RAFI AHMED KIDWAI AWARD: NOMINATION FORM

1. Name of theAward

: Rafi Ahmed Kidwai Award

2. Year Biennium 2001-2002

3. Name anddesignation of theScientist in full(underlinesurname)

Subramoney Narayana Moorthy

4 Date and place ofbirth

11 February, 1948, N. Paravur, Kerala

5. Marital status : Married

6. Complete Postaladdress

:Central Tuber Crops Research Institute,Sreekariyam,Thiruvananthapuram-695 017, Kerala, INDIA

7. Telephone , Fax,e.mail

0471-598551, Fax: (0091)471-590063, e.,mail sn_moorthy@rediffmail.com

8. Educational Qualifications beginning with the first-degree orequivalent (Tabular form)

Sl.No. Degree Institution Year

1 B.Sc. University College, Trivandrum 19672 M.Sc. IIT, Kanpur 19693 Ph.D. IIT, Kanpur 1975

9. Employment Record (In tabular form)

Positions held Year Organization Location

Jr. Development Chemist 1974-76 Hindustaninsecticides Ltd.

Alwaye,Kerala

Scientist B 1976-82 CTCRI TrivandrumScientist C 1982-85 CTCRI TrivandrumSr. Scientist 1986-1997 CTCRI TrivandrumPr. Scientist 1997

todateCTCRI Trivandrum

Any other relevant experience/training : (i). Attended Internationalcourse on Processing and Utilization of Tuber Crops at CIAT, Cali, Colombia duringMay 1986.

(ii). Underwent training in Starch Chemistry at the University of Nottinghamattached to Professor. J.M.V.Blanshard, and NRI, Chatham,UK for 6 months duringOctober 1990 to May 1991.

(iii). Attended First international Scientific meeting of the Cassava BiotechnologyNetwork (CBN) held at Cartagena, Colombia during August 25-28, 1992.

(iv). Attended International meeting Cassava starch and flour held at CIAT, Cali,Colombia during 11-14 January,1994.

(v). Attended XI the Symposium of International society for Tropical Root Cropsheld at University of West Indies, Trinidad and Tobago during 19-24 October 1997.

(vi). Worked as guest researcher at food technology division Lund University, Swedenduring April 98-March 99, attached to Professor A.C.Eliasson. Visited SwedishAgricultural University, Uppsala and Royal Danish Agricultural University, Copenhagenand Danish Technical University, Copenhagen, Denmark.10.

11. Details of the Research work submitted for the award

(i) When , where and how the research project was conceptualized?

The tropical tuber crops play a dual role in being a source of food as well

as industrial raw material. However, they have not received enough

importance due to various factors . The main factors are that the tubers

are considered poor mans crop and there is little awareness of the

variability available in the starch properties of these crops. Again the

knowledge about the innumerable products which can be produced

from starch has been scanty. So all these aspects needed to be

addressed to enhance the importance of these crops and research

projects were formulated and carried out covering food and industrial

applications of these neglected crops. In addition, an ad-hoc project on

minor tuber starches was undertaken in collaboration with RRL,

Trivandrum. Similar work was carried out during my advanced training

at the Food Science department of Nottingham University, and Natural

Resources Institute, UK and later on at Food technology department of

Lund University, Sweden during the Sabbatical leave . For use of

cassava as food , the cooking quality is very important and success of

any new variety depends on the acceptability by the consumers.

Previously only yield was considered important, but the role of quality

was realized and hence was accepted as essential criterion for

adoption. The experience gained from analyses of a large number of

samples was useful in formulating detailed studies on factors

responsible for good cooking quality of cassava tubers. The idea of

starch data bank which provides exhaustive data on different starches

and also starch bank having variety of starches with different

characteristics has been mooted and CTCRI having the most abundant

collection of root crops could best serve as the centre for this activity.

Hence a detailed study of the properties of all the tropical root starches

was carried out keeping in view effect of varietal variation and

environmental factors on the properties. Since there has been

increasing stress on value addition, processes for a number of products

based on the starches were developed which could in future make

these crops highly sought after. In view of the increasing demand for

environment -friendly products some of the technologies can be highly

relevant to the present day context.

(ii) When, where and how it was conducted ?

The work was carried out over a period of nearly 25 years and most of thework was conducted at the Crop Utilisation and Biotechnology division ofCTCRI, Trivandrum. Part of the work was also carried out at Food Sciencedepartment , University of Nottingham, NRI, UK ( 6 months ) and at FoodTechnology department , Lund University , Sweden (11 months).

In view of the importance of the tuber crops in food and industry, the work

on the cooking quality of cassava tubers, starch properties and product

development was taken up. First of all infrastructural facilities were built up

to carry out the work. Visits were made to ATIRA, Ahmedabad, CFTRI, Mysore

etc. and discussions with scientists and technologists working on starches

and related compounds were carried out. Based on the ideas thus generated,

equipments like Brabender Viscograph, FTIR and UV Visible

spectrophotometers were procured in addition to common laboratory

equipments. Books and journals related to starch and food were included in

the institute library. The cooking quality studies were carried out using the

tubers from varities available in the Institute. The studies on cassava starch

were instrumental in my getting deputed to UK . I carried samples of starch

and flour from different varieties and used the facilities available there. DSC

studies were carried out in detail on the starches. I also made use of this

opportunity to get acquainted with Deer Viscometer and Rheogonimeter. I got

training in Gel Permeation chromatographic studies of starch samples.

Similarly learned use of Coulter Counter for granule size measurement . A lot

of data on starch properties of tuber crops was generated and published in

International journals. Meanwhile a project on the minor starches was

undertaken in collaboration with Dr. Raja of RRL, Trivandrum financed by

ICAR-Cess Fund. When I got an offer for Sabbatical work at Lund University

to work with Prof Eliasson, an authority on starch, I carried with me the

different starch samples and studied their thermal properties using the

highly advanced Modulated DSC technique and generated voluminous data

on the tuber starches, especially interaction with lipids and surfactants.

Similarly detailed studies on rheological properties of the starches were

carried out and this is the first time that exhaustive work on rheology of

starches has been carried out. Since value addition is of utmost importance,

various products were developed from the tuber crops and their starches

which can have application in food and industry. Thus the results presented

are based on a concerted study carried out over a long period and covers

basic and applied aspects.

iii) What were the Socio- economic, technological and scientific relevance and priority of the research project ?

The tuber crops are considered poor mans crop in spite of the

fact that they provide food having high calorific and starch useful in

industry. Mostly they are cultivated by marginal and small farmers.

Except cassava they do not have any industrial base. The lure of cash

crops and easy availability of cereals and changing food habits are

futher threatening the survival of these crops. The crops can grow well

under adverse conditions (as recently proved by the experience of the

farmers during the Orissa Cyclone a few years back when only the tuber

crops survived ) and so it is necessary that these crops are retained in

the cropping schedule. This is possible only by value addition to a good

extent so that the farmers get good profit from these crops. The crops

can be very suitable for cultivation in North Eastern belts of the country,

but the major use will be as food and hence good cooking quality and

development of new simple foods need priority. Thus these are

important aspects which have been duly addressed.

The knowledge of starch properties of the tuber crops is scanty and

hence the awareness of their potential applications is limited. So the

studies on the tuber starches are very pertinent and can throw open

new vistas of their applications. In addition to providing basic

knowledge, the studies can throw light on the most desired

characteristics of starch which may be achieved by use of

Biotechnological tools. They can also substitute the chemically modified

starches which may have create health problems.

Product and process developments are becoming very important

in the present day context in view of the necessity to be competitive in

the world economic scene, Value added food and industrial products

with domestic and export potential need to be developed and has also

been given high priority in the work.

(iv) Who were the Principal Associate Scientists at various stagesof the research work?

1. Dr. C.Balagopalan, Former Head , CUBT Division, CTCRI,

Trivandrum

2. Dr. G.Padmaja , Head CUBT Division. CTCRI, Trivandrum

3. Dr K.C.M. Raja, Scientist G(Retd.) RRL, Trivandrum.

(v) What were the Principal milestones reached during the progress of the research work?

1. Based on the previous experience gained at IIT Kanpur anddiscussions with renowned Scientists in India working onstarch and related products, I was able to establish labfacilities for detailed studies on starch. The facilities havebeen made use of by other scientists of the institute and alsofrom other institutes,. Personnel from starch basedindustries also request our help in analyzing their products.

2. The cooking quality of cassava could be correlated tophysical changes occurring in the tubers during cooking likechanges in weight, volume and hardness.

3. Studies on the relationship of cooking quality of cassava tobiochemical parameters in the fresh tubers led to someinteresting results. Besides starch content, the starchproperties and presence of other ingredients along with starchalso influence the cooking quality.

4. . 5. A convenient method for the extraction of starch from

mucilaginous crops like Colocasia and amorphophallus wasdeveloped. The use of 0.03M ammonia not only led to higherrecovery of starch, but also better quality like colour,viscosity etc. In fact the procedure also was helpful in theextraction of mucilages from the crops

6. 7. The physico chemical and functional properties of different

starches were studied in detail and results showed a widevariability in the different starches unlike cereal starcheswhich show much less variability, In fact the results open upthe possibility of using these starches in lieu of thechemically modified starches.

8. Based on the studies on basic properties, it was also possibleto modify the starch properties by various physical, chemicalmethods which improved the properties while maintaining thedesirable ones.

9. The modified starches were displayed at various exhibitionsand their application and properties conveyed to industrialistsand entrepreneurs and visitors to the institute and hence theavailability of the technology was made aware.

10.Many industries have expressed their interest in theproducts and one Vensa Biotek purchased the technology forcold water miscible starch developed in our laboratory.

11. We have provides advise to many small scale units foradhesive production and oxidized starch

12. Based on the work on starch being done at CTCRI, it wasselected for hosting the XVI Carbohydrate Conference during2001.

vi) What were the principal results obtained and their scientific technological significance ?

During the period under report, I have been involved in three majorprojects in the institute, one ad-hoc project on physicochemical andstructural characterization of minor root crop starches and advancedtraining in starch chemistry in the UK and sabbatical at the Sweden.Three students also carried out their work under my supervision fortheir Ph.D degree. The work over the period covered a wide variety ofaspects which include studies on the cooking quality of cassava ,extraction process for starch from minor tuber crops, basic studies onthe starches of tropical root and tuber crops, production and propertiesof starch derivatives for application in food and industry and interactionwith industry and entrepreneurs for extension of technologies .The salient findings and results are outlined below under the differentheadings.

1.Cooking quality of cassava

For acceptance of cassava varieties for culinary purposes, cooking quality of

the tubers is of paramount importance..

A cassava variety is considered to possess good cooking quality if

the tubers are easily cooked and the cooked tubers should be soft, dry

and mealy . The poor cooking ones take long time to cook and are hard,

glassy and watery on cooking. Many varieties suffer from poor quality and

in addition, the quality is also influenced by environmental factors. Since

starch is the major component in cassava, it has a definite role in deciding

the cooking quality of tuber. Hence the role of starch and its behaviour in

presence of other biochemical components were examined in detail to work

out possible relationship with cooking quality For the study selected varities

having diverse cooking quality were used. Their cooking quality, properties

of the extracted starch and the behaviour of the starch in presence of other

components were investigated.

1.1. Physical changes during cooking.

First of all, a physical basis for assessment of cooking quality was

developed. Cooking is accompanied by swelling of starch granules and

imbibation of water during gelatinisation of starch and hence the change

occurring in the weight and volume of tubers during cooking was examined

at definite time intervals. The softness was measured using a fruit hardness

tester. The mealiness of cooked tuber was visually compared. The results

from a number of varieties revealed that the cooked tubers could be

classified into three broad categories based on the change in volume and

weight and softness after cooking (Table 1).

Tab 1. Physical changes in cassava tubers on cooking Category Cooking

quality

Appearance

of cooked

tubers

Vol. Wt. Softness*

1 Good Soft, mealy

and dry

+ 5-15% + 5-15% 5-15

2 Poor Hard, glassy,

sticky and

moist

0- -10% 0- -10% >20

3 Poor Disintegrated + >30% + >15% <3

* values in the fruit hardness tester (Scale 3-30)

It is obvious that too less or too much swelling of starch granules lead to

poor quality. The starch granules of good cooking varieties swell enough to

retain the granular integrity which provides the mealiness. The poor

cooking ones either do not swell to the desired level or swell too much. Too

less swelling results in non-mealiness and hardness while too much swelling

results in disintegration of the granular structure and release of the broken

starch molecules leading to cohesiveness and non-mealiness. The test

thus provides a physical method for determining the cooking quality of

tubers.

1.2 Starch content .

Since starch is the major biochemical component in cassava, the

role of

starch content was examined. The results with quantity of starch in tubers

having different cooking quality showed that varieties having low starch

content suffer from poor quality. Low starch content means that enough

starch molecules are not available to provide mealiness. It is also possible

that since the number of granules are less, they swell too much and

breakdown leading to non-mealiness. This is all the more true for under-

mature tubers which contain only less starch and always disntegrate on

cooking. It is difficult to arrive at the minimum starch content required for

good cooking quality, since some varieties having good starch content also

showed poor quality. But a minimum starch of 25% starch could be

considered imperative for providing cookability.

1.3.Starch properties.

Since it was clear that starch content alone did not decide

the cooking quality, a study of the starch properties was also undertaken.

Starch extracted from different varieties by standard method was examined

in detail for various properties and the results are discussed below.

1.3.1. Granule size.

Though microscopic studies did not show any wide variability in

average granule size among the different varieties, (Tab 2) Coulter counter

studies indicated that there is variation in the distribution pattern among

the granular sizes. Thus H-1687 starch showed a higher frequency in the range of 13-16

m and relatively less in the range of 6-13 m compared to H-165, H-97 and S-856 starches.

Variety M-4 also had a slightly different distribution pattern, but not as prominent as H-1687

starch [Pub.1]. Though the exact role of the granule size in deciding cooking quality is not clear,

it is seen that these two varieties are better cooking than the others . .

1.3.2. Crystallinity.

Starch has well defined crystalline structure owing to the well

ordered regions in the amylopectin portions. The starches from five

cassava varieties examined exhibited ‘A’ pattern and no difference in the ‘d’

spacing was evident. The Absolute crystallinity of starch determined from

the Xray Diffractograph also did not vary very much among the different

varieties.

( Tab 3 ]. Similarly the flours from these varieties had nearly similar

Absolute crystallinities

1.3.3. Molecular weight.

The molecular weight determined by Ferricyanide method, alkali

value and peroiodate methods did not show any definite trend and it was

concluded that there is only very little difference among the varieties. ( Tab

2] Pub 2]

1.3.4. Amylose content. The amylose content of the extracted starches determined

iodimetrically exhibited only slight variation among the different varieties

and may not be contributing very much towards quality. The soluble

amylose content also showed only little range suggesting very little role [Tab

2]. It has been suggested by some workers that the soluble amylose present

in the amorphous regions of the starch granules may be responsible for

stickiness in tubers. Such an effect is not evident in the present studies .

Gel Permeation Chromatographic analysis was also carried out on these

starches to find out if differences exist in the chain length and Degree of

Polymerisation . Starch was treated with isoamylase and the resulting

debranched starch was subjected to reverse phase GPC using Fructogel

columns. The fractions were collected and their carbohydrate content was

determined by the phenol sulphuric acid methods and the reducing value of

each fraction was determined by ferricyanide method. The chain length was

calculated by dividing the carbohydrate content by reducing vale and was

plotted against the elution volume. The figures [Fig 2] showed only slight

variations in the GPC patterns and no clear relationship was evident

leading to the conclusions that amylose contents and chain lengths are

almost similar among the varieties.

1.3.5. Swelling volume and solubility.

Values for swelling volume determined by allowing free swelling of

the granules in excess distilled water exhibited considerable difference

among the varieties. Starch of varieties like M4 had lower swelling volumes

compared to varieties like H-165 ( Tab ] . Higher swelling can lead to

weakening of intermolecular forces between the starch molecules resulting

in easy breakdown so that the granules do not have the granular integrity

required for mealiness. Thus swelling can be one of the key factors in

deciding the mealiness of cooked tubers. This is further supported by the

fact that during growth period, starch of variety M4 maintains uniform

swelling volume and swelling power [Fig 3], Publ.3 and the variety has

excellent cooking quality. Similarly solubility which provides insight into the

strength of starch granules also was constant for starch of M4.

1.3.6. DSC patterns.

Differential scanning calorimetry is an important tool to study

starch gelatinisation and provides wealth of information on starch structure.

The DSC patterns of starch from five varieties were obtained using a Perkin

Elmer DSC equipment (Fig 3). The thermograms showed distinct features

for some varieties. Starch of H-97 exhibited a typical pattern with a shoulder

which could not be removed either by defatting or ethanol extraction

showing that this pattern is genetically controlled and the starch may be

containing two types of granules having difference in their intermolecular

forces. Similarly the broad nature of the thermogram of starch of M4

indicates that the crystallites melt very slowly during gelatinization, again

highlighting higher strength of associative forces in this variety.

Intermolecular strength has a definite role to play in maintaining the starch

granular integrity during cooking and this is borne out by the DSC

behaviour of M4 starch.

1.3.7 Gelatinisation temperature.

The ease of gelatinisation can also play an important role in starch

swelling and hence the gelatinisation temperatures of starch of different

varieties determined microscopically were compared. . The results (Tab 2)

indicated that H- 165 starch gelatinized relatively earlier. Early

gelatinisation means that the gelatinised granules are being subjected to

longer periods of heating leading to higher breakdown of the starch

molecules and thereby resulting in poor quality. Gelatinisation

temperatures obtained from the DSC also showed that H-165 starch had

slightly lower values confirming that this starch gelatinized more easily and

hence possessed relatively weaker associative forces.

1.3.8 Pasting temperatures

Pasting temperature which indicate the temperatures at which a

perceptible increase occurs was determined in the Brabender viscograph

using different concentrations of the starch in distilled water. The results

obtained further confirmed earlier gelatinisation by H 165 starch. M4 starch

exhibited a high gelatinisation range showing the stronger intermolecular

bonding. Thus slow and steady gelatinisation of starch is preferable to early

and rapid gelatinisation so that the starch is able to maintain its

structural integrity.

1.3.9. Viscosity

Viscosity in an important property of starch and was determined for the different varieties

using a Brabender viscoamylograph at different starch concentrations. There was clear

difference in the patterns for the starch of different varieties. Broadly the patterns could be

classified into three

1. Single stage gelatinisation with high peak viscosity and high viscosity breakdown

2. Two-stage gelatinization with high peak viscosity and breakdown

3. Broad two-stage gelatinization with medium viscosity and medium breakdown

It was observed that H.1687 starch had a medium peak viscosity, low viscosity breakdown

but high set-back viscosity. M4 starch had slightly lower peak viscosity and setback viscosity.

On the other hand, H 165 starch had a very high peak viscosity and the breakdown was also

quite large. The viscographs clearly indicated that for H-165 starch, the set-back viscosity was

much lower compared to peak viscosity, whereas for H-1687 starch, the reverse was true (Fig.

4). The results indicate that -starch of H-165 undergoes rapid increase in viscosity and under

shear and heat suffers breakdown. This leads to cohesiveness for the paste brought about by the

broken starch molecules and hence poor quality. On the contrary, starch of M4 and H-1687 do

not exhibit high viscosity rise and hence suffer lower breakdown. These two varieties have better

cooking quality and hence viscosity behaviour can play a major role in deciding cooking

quality. These patterns seem to be genetically controlled as they were maintained by these

starches irrespective of the environmental factors, though there was variation in the viscosity

values.

1.4. Effect of other ingredients

Often it is found that tubers having high starch content and desirable rheological

characteristics do not cook well and others factors like environmental conditions and age of the

crop influence the cooking quality. Again the starch properties determined after extraction need

not truly represent the real condition in the tubers . The starch granules have to swell in lower

water regime and also in presence of various other components. So this aspect also has relevance

in deciding the cooking quality. The major factors present in the tubers are fibre, sugars and

much smaller quantities of proteins and lipids and minerals. These factors were determined and

their effect on the starch properties were studied. Calcium which is known to have a firming

effect on potato tubers and phosphorus being always present in starch were also estimated.

1.4.1 Distribution of starch and sugars in different parts of the tubers. Congo red staining of cooked tubers of different varieties indicated variation in starch content

in different portions of the tubers. A more uniform distribution was observed in better cooking

varieties. In order to confirm the results, the starch, sugar and dry matter contents of different

portions of the tubers were determined. In addition, the starch was extracted from these areas

and their swelling property examined. . Hence it is clear that of Other biochemical

constituene and hence other factors also decide the quality. There was no

swelling

Next the biochemical principles and their role were examined. For the study,

the tubers of eight varieties having different cooking quality were selected

and the starch, sugar, fibre contents were determined. In addition, the Ca

and phosphorus contents were determined. The starch and sugar contents

in the outer, middle and core portions of the tubers were also determined. It

was evident that starch content is an important factor in deciding the

quality. Tubers having low starch content did not cook well. The Calcium

and phosphorus contents showed only very minor variation and there was

no noticeable relationship between their content and cooking quality. Use

of Calcium sequestering agents like during cooking also did not bring about

any improvement in cooking quality of poor cooking varieties confirming

that Ca may not have an important role in deciding cooking quality.

1.4.2 Effect of other ingredients on starch swelling. In order to check the effect of the non-starchy components on the starch

properties, the properties of the flour obtained from the different varieties

were examined. These included DSC pattern, XRD pattern, Swelling

volume and viscosity parameters. The results clearly brought out the

influence of fibre present in the tubers on starch gelatinisation. Whereas

absolute crytallinity , XRD and DSC patterns were hardly affected, the

viscosity behaviour and swelling characteristics were influenced

considerably by the fibre. There was noticeable reduction in swelling and

peak viscosity of the starches in presence of fibre. The fibre acts as a partial

barrier to free entry of water molecules during gelatinisation and hence

allows only restricted swelling. The viscosity patterns are modified by the

fibre in imparting lower viscosity breakdown by cementing the starch

molecules against breakdown under shear and temperature. It was also

seen that defatting by hexane or extraction with methanol to remove lipids

and sugars hardly affected the swelling and viscosity patterns again

confirming that it is the fibre rather than fat or sugars that exert higher

influence on the starch properties. This fact is further confirmed by the

swelling and viscosity behaviour of the starchy flour obtained from

inoculum provided fermentation of tubers. The starchy flour thus obtained

contains large quantity of fibre and they modify the starch properties

favourably. In fact it was observed that food products made from flour

possess less stickiness compared to those made from starch alone. So fibre

has a definite role in deciding the starch properties.

The examination of the effect of the tuber extracts on the starch

properties also provided interesting results. Fresh tubers of different

varieties were crushed and squeezed out to provide the extracts. The isolated

starch from different varieties was allowed to swell freely in the extract and

the swelling volumes and viscosity studied. Whereas the extract of M4

enhanced swelling of all extracted starches, the extract of H165 tuber

brought about a reduction in swelling and viscosity . The sugar content in

the extract of H-165 was found to be relatively higher. It is well

documented that sugars have the capacity to increase the solubility of

starch and hence may be contributing to breakdown of starch and thus

lowering the cooking quality. The observation that tubers harvested

immediately after a rain following a drought contain higher sugars and

suffer from poor cooking quality further confirm this fact..

The main conclusion from the study of cooking quality was that the

cooking quality of cassava tubers cannot be attributed any single factor, but

an interplay of many factors. The major contributing factors are as follows

1. Starch content. There should be reasonable starch content. An exact

amount cannot be fixed but tubers having less than 25% will be hard

to cook. Uniform distribution of starch in the tubers and stability of

starch during growth period are desirable.

2. Presence of other components. Fibre and sugar affect swelling of

starch. Whereas fibre restricts swelling and thereby prevents viscosity

breakdown , sugars impart higher solubility to starch. So some small

quantity of fibre along with starch can lead to better quality.

3. Starch property. Starch property is an important criterion in deciding

the quality. Whereas very low swelling is not desirable, too much

swelling can lead to granular structural disintegration and thus

poor quality. Stability of viscosity and reasonable setback are

desirable.

The data thus generated can be used by the breeder to produce varieties

having desirable traits for cooking quality.

2. Extraction of starch Unlike the cereal and potato starches which have found

industrial uses since long, the root starches have not received much attention except cassava and to

some extent sweet potao starches. This can be attributed to two main factors. One is the difficulty in

extraction of starch from the tubers other than cassava and second factor is lack of knowledge

about their properties. Hence both these factors were taken into consideration for studies in detail.

Whereas extraction of starch from cassava is simple and the isolated starch is pure white in

colour and relatively free from other impurities, starch extraction from other tuber crops is not

so easy. The settling of starch granules is hindered by presence of various components like

mucilage, latex etc. and this leads not only to loss of starch, but also lowering of quality of the

extracted starch. The long residence time can bring about microbial contamination leading to

breakdown in starch and resultant loss of starch quality. In addition, the colour of the starch is

also affected so that the acceptability of the starch in applications like food - especially sago -

and textiles suffers. Work was carried out at CTCRI on use of various chemicals in

improving the yield of starch from various tubers. It was observed that among different

chemicals tried, ammonia gave best results, Tab. 1 [5]. The extraction of starch from different

tubers using ammonia (0.03M) not only improved the yield, but also the functional

characteristics like paste viscosity and swelling. Ammonia acts by reacting with the

mucilaginous compounds allowing the starch granules to settle fast. Use of lactic acid and citric

acid improved the yield of starch from sweet potato tubers and also the colour of the extracted

starch [6]. A detailed study on use of five chemicals in varying concentrations revealed that

the yield varied considerably for the different starches at different concentarions of the chemicals

examined, but ammonia appeared more effective in improving the yield of starch from aroids

and yams. Table [7, 8] The quality of sweet potato starch extracted using the enzyme

combination of pectinase and cellulase was studied and the results reveled that the enzymatic

extraction did not bring about any detrimental effect on the starch properties. [Pap].

3. Basic studies on the tuber starches.

Once the extraction of starches in good quantity and quality from most of the tubers was

achieved, a detailed study of the physicochemical and functional properties of the different tuber

starches was carried out in the Institute and the results are outlined below

3.1 Other components in starch

Even though starch extracted from the tubers appear white and pure, still it harbours many

other biochemical components like moisture, fibre, lipids, sugars, minerals which influence the

starch properties.

The moisture content varies from 6-16% depending on the process used for drying the

starch. The fibre content can show much higher variability depending on a number of factors like

the sieve used for removal of the fibrous material, varietal variation and age of the crop. These

factors are all the more important in cassava and sweet potato, where the fibre content increases

with the maturity The presence of the fibre modified most of the rheological and functional

properties of the starches [14]. The effect of fibre on starch properties is also clear from the fact that

cassava flour (containing 2-3% fibre) had different swelling and viscosity properties compared to

the isolated starch (having 0.1-0.15% fibre) and neither defatting nor ethanol extraction brought

about any major change in the properties of the starch or flour [15]. The total dietary fibre in

cassava flour was found to vary between 4.7 to 5.5% . For Coleus starch 0.4% fibre content was

observed [16]. It has been found that the fibre content in the extracted starch from cassava tubers

subjected to fermentation with inoculum provided culture contained considerable quantity of fibre

[11].

The tuber starches contain much lower quantities of lipids in them and so the effect of

lipids on starch properties is not so pronounced compared to cereal starches. The lipid content in

different cultivars of cassava was found to vary from 0.11 to 0.22% in starch and 0.27-0.45% in

flour of five varieties [15] . Lipids and surfactants form complexes with amylose chains and the

free chains of amylopectin and thus influence starch properties. Based on this principle, it has been

possible to improve the viscosity stability of cassava starch by treatment with surfactants It has also

been established by Modulated DSC studies that there is no hindrance for the tuber starches to

complex with surfactants or lipids even though the native starches do not contain much lipid in

them [18,19]. . The tendency of amylose to form complexes with lipids and surfactants has also

been made use of in determination of amylose content in starches using Modulated DSC [21, 22]

Another important component invariably present in starch is phosphorus, since P is involved

in starch synthesis. Studies on the P content in cassava starch during growth period did not reveal

any major variation with age of the crop for six cultivars over the growth period of 2- 18 months

[23]. The P content in different Colocasia cultivars varied from 0.006 to 0.013% [24]. Studies on

the P content in six accessions of D. rotundata showed only very minor variability (0.011-0.015%)

[25]. Examination of starch from three cultivars of Canna edulis from CTCRI revealed that the P

content ranged from 0.05 to 0.08% which is even higher than that found in potato starch [26].

Similarly it has been found that Curcuma starch also harbours high quantity of P (0.045%) [27]. The

high phosphorus content can impart high viscosity to starch and also improve the gel strength. The

high viscosity is attributed to the repulsion between the ionic phosphate groups. This was evident in

the case of Canna starch which has high viscosity and good gel strength. Biscuits made from the

starch were having good texture and crispness. These starches can also be very useful in food

applications requiring good gel strength like jellies etc.

2. 3. Colour and appearance

Colour is an important criterion for starch quality, especially for use in sago and textile

industries Use of organic acids also was helpful in improving colour of sweet potato starch. The

starch extracted from Colocasia and Dioscorea tubers by normal process always has an off-colour

which is difficult to remove. However use of ammonia during extraction was found to improve

considerably the colour of the starch from aroids especially Colocasia [5]. Though tubers of some

varieties of Amorphophallus possess yellow colour in their flesh, the resultant starch is pure white in

colour. If the extraction is proper, the colour remains white even during storage for six months.

2. 4. Granule size and shapeCassava starch granules are mostly round with a flat surface on one side containing a

conical pit, which extends to a well defined eccentric hilum. Some granules appear to be compound

[3]. Under polarised light, a well defined cross is observed. Sweet potato starch is polygonal or

almost round in shape and has a centric distinct hilum. Polarisation crosses are less distinct

compared to cassava starch. Yam starches have a large variability in shape, round, triangular, oval

and elliptical. Some of the elliptical granules are found to possess truncated ends [3]. Colocasia

starch granules are mostly round or oval and the hilum is observed only with difficulty.

Amorphophallus starch granules are mostly polygonal or round in shape and have faint hilum. We

obtained oval and polyhedral shape for Canna edulis starch granules [26]. Curcuma starch granules

are elliptical in shape like D. rotundata and canna starch granules [27] (Tab. 2). The size of the granules is also quite variable among the tuber starches (Tab. 2).

Cassava starch was found to have a size range of 5-40 m. . Studies on the starch granule size

variation with age of the crop starting from 2nd month till 18th month for six varieties revealed

that size increase was observed upto 6th month, but then remained steady [23]. Colocasia

granules are much smaller (range of 1-10 m) and are among the smallest of starches observed

in the plant kingdom. The small granule size makes the starch useful in various applications eg.

as a filler in biodegradable plastics, in toilet formulations, aerosol etc . Unlike other tuber

crops, which do not exhibit any significant variability in size among varieties, Colocasia starch

was found to exhibit varietal difference. Studies on 10 varieties revealed a significant

difference in average granule size (Fig 2, Tab. 4 ). Variety C-9 was found to have the highest

value of 5.19m and C-46 the lowest (2.96 m) [24]. The granules extracted from corms and

cormels of four cultivars of Colocasia were compared and it was found that there was very little

difference between them [30]. Even the distribution of the granule sizes showed only minor

difference between the corms and cormels. It was also found that though there was variation

among the cultivars, there was no significant variability during the growth period. Such varietal

difference was not observed in Dioscorea alata, D. rotundata and D. esculenta starches.

These starches showed an increase in granule size upto 5 months and thereafter remained steady.

One noticeable feature is that D. esculenta granules are very small, while the D. alata granules

are very large. The granules of D. esculenta possessed an average size of 2-15 m, close to

Colocasia starch. The small granule size of D. esculenta may be useful in applications similar

to those of Colocasia and cereal starches. Starch granules of D. alata and D.rotundata are

much bigger, the range is between 6-100 m for D. alata (average 35 m) and 10-70 m for

D.rotundata (average 33 m) starches. No significant difference in granule size among the

different varieties of three yam species studied viz. D alata, D. esculenta and D. rotundata was

observed.. There was only minor variation in starch granular size among 10 accessions of

Amorphophallus studied.(Tab. 5) [31] . Xanthosoma starch granules range from 10-30m

in size with an average value of 17 m, and no difference among accessions was observed.

Coleus starch granules had a a size range of 5-20m [16]. Pachyrrhizus starch was found to

have a size range of 7-40 m, and very little difference among varieties. . However the largest

granule size was observed for Canna edulis starch The average granule size was found to be

over 35 m for three varieties of Canna [26] The granule size was in the range of 16-58 m

for Curcuma zedoaria and 14-46 m for C. malabarica starches [27]

2.5. Spectral featuresThe infrared spectrum of starch of different varieties of cassava was found to be similar

with peaks at 3600-3200 (broad), 2800 (medium), 1660 (weak), 1480-1250 (medium) and a

number of peaks between 1150 and 710 cm –1.

FT-IR of the different tuber starches revealed only very minor differences, in spite of

their different crystallinity and granule sizes. The Raman spectra of the tuber starches indicated

distinct differences in the peak pattern in the region 800-200 cm-1 (fig )[32]

THE CP- MAS 13C NMR of the different starches showed typical pattern for the starches

and three main peaks were observed. The first peak was at 101-102 ppm corresponding to C1

and appeared as a singlet or doublet depending on the source of the starch. The next peak

appeared at 75-80 ppm corresponding to C2,3,5 and was a singlet. The final peak was at 64 and

a singlet. The peaks were observed only if the starch granules had 8-10% moisture in them.

There was clear correlation between the XRD pattern and the NMR peak pattern. Whereas the

starches having pattern ‘A’ showed a doublet for C1 peak in NMR, those with ‘B’ pattern had

clear singlet C1 peak (Tab. 6; Fig. 3). Thus the structural difference between the two types of

starch is evident.

2.6. X-ray diffraction patternStarch has a definite crystalline nature and the crystallinity has been assigned to the well

ordered structure of the amylopectin molecules inside the granules. . Cassava starch has been

found to posses ‘A’ pattern with three major peaks at 2Ø=15.3,17.1 and 23.5° [3] . As already

mentioned there was not much variation in absolute crystaniilty among the varieties. The flour

also possessed similar pattern and the starchy flour obtained from tubers subjected to inoculum

provided fermentation. Sweet potato starch was found to possess ‘A’ pattern. Colocasia,

Xanthosoma , Pachyrrhizus, Arrowroot and Amorphophallus starches also possessed ‘A’

pattern [3] . But the edible Dioscorea starches (viz. D. alata, D.esculenta and D. rotundata)

possessed ‘B’ patterns similar to potato. It was found that the XRD pattern of extracted starch is

same throughout the growth period of D. rotundata (Fig. 4). Starch of Canna edulis and

Curcuma sp. exhibited ‘B’ XRD pattern. A detailed study of the XRD parameters of the

starch extracted from Amorphophallus and Xanthosoma tubers subjected to pre-treatment using

different chemicals was carried out. The ‘ d’ spacing, angle intensity and peak intensity were

found to be similar for control (water) and chemically pretreated samples of Amorphophallus

samples. However shift occurred for the peaks indicating partial change in the crystalline phase

[7,8, 33]. For Xanthosoma starch, higher concentration brought about more significant changes

especially with potassium metabisulphite. Heat moisture treatment did not change the XRD

pattern of D. rotundata starch [34].

2.7. Molecular weight The molecular weight of cassava starch showed only minor differences existed

among the different varieties (Tab. 3). D. rotundata starch showed only minor changes in

the molecular weight over the growth period [25]. Colocasia esculenta and Amorphophallus

paeoniifolius starch from different varieties had almost the same range of reducing values,

showing that the tuber starches have nearly equal molecular weights. Studies on the yam and

aroid starches extracted from tubers subjected to treatment with different chemicals also

indicated only very minor differences in the reducing values among the different treatments

[7,8,33]. For coleus starch, the reducing value was 1.71, indicating the same range as for other

tuber starches [16] while it was between 1.7 to 2.1 for Curcuma starch [27].

2.8. Amylose contentThe linear component of starch, viz., amylose, imparts definite characteristics to starch

and therefore amylose content is an important criterion in determining the starch properties .

Amylose content is found to vary considerably among different starches and even genetic

modifications have been carried out to obtain starch of amylose contents varying from 0- >75%

amylose.

It was found that the Blue Values corresponding to total amylose varied from 0.50 to 0.55

for seven cassava varieties, indicating only very minor variation among the varieties [29]. When the

amylose content of six varieties of cassava was compared during growth period, there were only

insignificant differences in the amylose content [23]. . Examination of the effect of surfactants on

the amylose content in cassava starch revealed that though the surfactants reduced the Blue Values,

there was no correlation between concentration of surfactant and reduction in Blue Values [17].

Maximum reduction was obtained with cetyl trimethyl ammonium bromide while lowest reduction

was with potassium stearate. Sodium lauryl sulphate and cetyl trimethyl ammonium bromide,

having bulky hydrophilic groups, might be blocking the entry of the iodide into the amylose helix.

Colocasia esculenta starch had wide range in the amylose content and noticeable

relationship between the amylose content and granule size was noticed. The variety C-9, which had

the largest granule size also possessed the highest amylose content [24]. . Amylose content in six

D.rotundata varieties ranged from 21 to 24.6% [25] while that in D. esculenta and D.alata in the

range 20-26%. Thus the amylose content also varies considerably among the Dioscorea starches.

The starch of D. esculenta, D. alata and D. rotundata was also examined for total amylose content

in relation to age of crop. The results indicated only very little variation in the amylose content with

age of the crop. Xanthosoma starch also had a similar amylose content viz. 15-25% and very little

varietal variation was observed. The amylose content of ten cultivars of Amorphophallus

paeoniifolius was found to vary very little and ranged from 21.9-23.5% [31]. Starch from three

accessions of Canna edulis was found to have an amylose content ranging from 24-30% , the

highest being observed for purple accession [26]. Coleus starch had an amylose content of 33% [16]

. Thus among the different tuber crops, Canna edulis and Coleus starches have highest amylose

contents (Tab.8).

Soluble amylose is an important component in starch which plays a significant role in

deciding the textural properties. The amylose molecules in the amorphous regions are supposed

to make up this fraction and so are easily leached out and hence responsible for cohesiveness in

cooked tubers The soluble amylose contents in the tuber crops starches determined using

iodimetry ranged from 10-40% of total amylose. Soluble amylose content in different varieties

of cassava was found to be almost equal, even during the growth period. Similar trend was

observed for Colocasia, D. alata and Xanthosoma starches. For Amorphophallus starch from

different accessions, the soluble amylose content ranged from 9-11% forming nearly 45% of the

total amylose content [31]. The soluble amylose content in Coleus starch was 12.8% [16] while

it ranged from 10-12% for Canna edulis starch [26].Results on the complexation of tuber starches with the surfactants were quite interesting in

that the soluble amylose was suppressed to different levels with different starches and different

surfactants. In case of cassava starch, the surfactants had variable effect on soluble amylose portion.

The anionic surfactants potassium palmitate and potassium stearate and the neutral surfactants

glyceryl monosterate had little suppressive action but the cationic surfactants cetyl trimethyl

ammonium bromide and sodium lauryl sulphate had significant effect. Increase in concentration of

these surfactants led to reduced blue values for soluble amylose[17].

The effect of the cationic surfactant cetyl trimethyl ammonium bromide on the other

tuber starches is even more interesting (Tab. 9). Though the surfactant reduced the blue value

for soluble amylose of all the starches, the effect on Colocasia and D. esculenta starches was

more prominent indicating that the soluble amylose of these two starches may be more anionic

in nature or that the amylose helix of these two starches are such as to be able to sterically

favour the complex formation. It is worthwhile noting that these two starches have the lowest

granule size, but no correlation between complexing properties and granular size could be

observed for the other starches

2.9. DSC characteristics

Differential scanning calorimeter (DSC) has become an important tool in studying

starch gelatinisation. The method is simple, fast, requires only small quantities of sample and

gives reproducible results. Now the advanced version of DSC, viz., Modulated DSC can give

more valuable information regarding gelatinisation, glass transition and starch-lipid complexes.

Comparison of the DSC parameters among different tuber starches revealed not only

large variation among the different starches, but also between different samples and

experimental conditions used like moisture content, rate of heating etc. used [37,38]. The DSC

data obtained by us by using normal DSC and MDSC is presented in Tab. 11 and Fig. 7. The

effect of reheating the sample after one cycle has also been studied. The general trends which

emrged from the study of 11 tuber starches are outlined below. Among the different tuber

starches, cassava and sweet potato starches generally had lower Tonset and Tend values. Highest

values were noticed for Colocasia starch and the other starches had values in between. The

range of gelatinization varied from 8-10°C for the starches. Thus wide variation is evident

among the different studies. DSC of the starches from the two curcuma varieties indicted that

the gelatinisation peak of C. malabarica starch was a doublet and the splitting of peak may

be attributed to some structural differences in the starch [27]. . The range of gelatinization was

higher (17-22C) for curcuma starch and similar to yam and potato starches . This can also be

attributed to the presence of phosphate linkages in these starches.

Thus it is evident that there is considerable variability in the

gelatinisation temperatures among the different tuber starches. The

difference in the gelatinisation temperatures can be traced to the

variation in the starch intermolecular bonds. High temperature of

gelatinisation can be indication of higher stability of the starch

crystallites in the starch molecules which means more heating is

required to swell the granules. In addition, a number of other factors like

varietal differences, environmental conditions and the experimental

protocols like level of moisture, sample preparation, rate of heating and

instrument used - all contribute to the values.

The range of gelatinisation is also quite different among the different starches. In our

study, we obtained highest range for cassava starch (12.90°) and lowest for Xanthosoma

starch (4.7°) [38]. However here also lot of ambiguity exists among different reports and can be

attributed to a number of factors . Higher range has been attributed to higher level of

crystanillity which imparts higher structural stability so that the water molecules need longer

time to penetrate the crystalline areas . There does not appear to be any relation between the

XRD pattern and gelatinisation range, as both cassava and Xanthosoma have ‘A’ pattern but the

range of gelatinisation are far different. An ‘A’ XRD pattern indicates closer packing and should

have a higher range of gelatinisation, but such an effect is not observed. In addition , the Tonset

does not appear to be influencing the range of gelatinisation in any regular pattern. Similarly

granule size and gelatinisation range do not show any relationship. In the Brabender

viscographic curves, the yam starches show a longer range which does not appear in the DSC.

The difference in the water: starch ratio between Viscography and DSC may be reason for this

anomaly.

Gelatinisation enthalpy is another important parameter obtained by DSC. The value

depends on a number of factors like crystallinity, intermolecular bonding etc. For cassava starch

values of 12.4 and 16.6 J g-1 were obtained by us. The enthalpy of gelatinisation of five

varieties of cassava varied from 10.6-13.8 J g-1 [15]. Gelatinisation enthalpy was also found to

depend on the genetic and environmental factors . Effect of variety and environmental

conditions was also evident . The gelatinisation enthalpy was 12.9 J g-1 for Colocasia starch and 16.6 J g-1 for

Amorphophallus starch [37] . For D. alata starch our values were 11.6 and 15.4 J g-1 . For

D. rotundata starch values of 10.28 and 15 J g-1 were recorded . For Xanthosoma starch the

enthalpy was 9.1 and 15.22 J g-1 in the two studies . We obtained enthalpy value of 17 J g-1

for Canna starch . Here also there does not appear to be any relationship between the enthalpy

and other factors like amylose content, granule size and XRD patterns. Since the amylopectin

has a more crystalline nature, higher amylopectin content has been considered to contribute to

higher enthalpy of gelatinisation. However such an effect is not evident in any of the studies.

Again the differences do not reflect the structural differences among the tuber starches. The

results also show that unlike the gelatinisation temperatures which show wide variation, the

enthalpy of gelatinisation is within in a small range for the tuber starches.

DSC has been quite useful in studying retrogradation properties of starches. Starch

retrogradation is another aspect in which lot of vagueness exists. Originally it was assumed that

retrogradation occurs by association of the amylose chains. But using waxy starches, it has been

established that amylopectin can also take part in the retrogradation by the association of the

outer chains Retrogradation parameters of tuber starches have been examined by DSC, but the

results were quite erratic and hence difficult to arrive at definite conclusions [38] . The values

for Tonset showed very wide range from 37° to 58°, highest and lowest being for arrowroot and

Xanthosoma starches respectively. It is well known that retrogradation brings about drastic

reduction on Tonset of starches. The highest reduction was observed for Amorphophallus and

lowest for D. esculenta starches. The range also varied widely from 12.2°C for cassava to 43°C

for D. alata. The wide range in values indicates that the retrograded starch contains

recrystallised amylopectins of different crystanillity. Among the starches D. alata starch

appears to have the maximum variability in crystalline structure. . The reduction was to the

extent of 2.5 fold to 7 fold. No relationship could be derived from the properties of retrograded

starches with those of the nonretrograded starches [37].

MDSC in starch gelatinisation

The tuber starches were studied in detail using MDSC . MDSC uses a continuous heating-

cooling cycle which is helpful in identifying reversible and non-reversible processes occurring in

polymers. Gelatinisation of starch is a non-reversible process whereas melting of the amylose-

lipid complex is reversible one. In the normal DSC, the latter is studied by subjecting the starch

to cooling after the first run and then re-heating it so that the gelatinisation peak does not appear

during the second heating. Since MDSC separates the two processes, MDSC should be better in

studying the two processes. It was with this presumption that MDSC studies were carried out on

various starches .

MDSC was run on a Seiko SII 6200 DSC equipment provided with an built-in software.

. The samples were directly weighed into coated aluminium pans. Double distilled water was

added to get a water-starch ratio of 2:1 and empty aluminium pan was used as reference. The

heating cycle used was as follows: first heating from 15C to 150C at the rate of 3C /min,

cooling to 30C at 30C/min; second heating from 30 to 130C at 3C/min and final cooling to

30 at 30C /min. Using the built-in software the thermogram was resolved into reversible,

irreversible and total peaks. The gelatinisation onset (To ), Gelatinisation end(Te ) and

gelatinisation enthalpy (H) were determined from the thermographs and corrected for dry

weight. The results were expressed as mean of at least three values.

Some of the graphs obtained for the different starches are given in figures. The graphs

corresponding to total contains both the reversible and irreversible changes taking place during

gelatinisation.. The starch gelatinisation is an endothermic process which involves absorption

of water by the starch and swelling and it is an irreversible process. . The second peak

corresponds to the melting of the starch-lipoid complex which is formed between starch and lipid

and the peak depends on a number of factors like concentration, lipid type and heating

conditions.

In modulated DSC, the heating takes place in stages, in which there is continuous cycles of

heating and cooling and it is claimed that it is able to separate the reversible and irreversible

processes taking place during the runs. It is expected that therefore it should be possible to

separate the starch gelatinisation and starch-lipid complex melting. So during the splitting of the

total peak into K (kinetic) and C modes, the irreversible transformation viz. gelatinisation

should appear in the K graph while the reversible viz. starch-lipid melting should be only present

in the C graphs. However the result shows that such a clear separation does not take place.

Whereas the H for K is invariably lower compared to S(Total) , the C graph invariably

contains some peak corresponding to the starch gelatinisation which should not be there . This

indicates that the separation of S into K and C does not strictly follow the reversible and

irreversible pattern. It is also quite possible that the so-called gelatinisation of starch is not fully

irreversible and may contain reversible processes also. This is invariably true for all the starches

examined The absence of peak for starch-lipid melting during the secod heating cycle proved

beyond doubt that the tuber starches do not contain any naturally bound lipids in them. The

result is interesting in that Pacchyrrhizus plant produces pods and so it can also be considered

as a leguminous crop. The starches from leguminous crops usually contain native lipids and

show the starch-lipid melting endotherm. The absence of such a peak in the DSC of

Pacchyrhizus starch shows that the starch has more similarity to tuber starches rather than

legume starches.

Starch-surfactant complexation in determination of amylose content in various starches

The starch –surfactant complexation has been used for determination of amylose in the

tuber starches. The principle behind this method is comparison of the enthalpy values of the

starch-lipid melting with standard amylose. The method has many advantages over the other

common methods. Iodimetric method is very sensitive to pH and often provides inconsistent

results due to the difficulty experienced in dissolving starch to get uniform solution.. GPC

method is long and is also not so reliable. The DSC method is very simple and requires only

very small quantities of the sample . The principle behind the method is that when a lipid or

surfactant is added to starch, it binds with the amylose fraction of starch. The measure of

enthalpy of melting of complex can give the estimate of amylose content in starches. It has also

observed that whenever the complex is cooled and reheated, the enthalpy during second heating

is higher compared to first heating. In addition the Tonset is also elevated. This indicates that

during first heating when starch gelatinises, the amylose portion is released and hence can form

complex with the lipid or surfactant. So if the process is repeated, the complexation becomes

more strong. In modulated DSC, there is continuous heating-cooling cycle during each run and

hence it can be considered as a series of heating and cooling operations. So this method should

give better results. This is the principle behind use of MDSC in amylose determination. Another

drawback in the earlier method which uses DSC is use of the lipid lysolecithin which is quite

costly. So we tried use of easily available surfactants viz. Sodium dodecyl sulphate(SDS) and

cetyl trimethyl anmmonium bromide. (CTAB)

The experimental technique involves weighing out 2-5 mg starch into the pans, addition of

5% solution of the surfactant, so that the starch : water ratio is 1:2. After sealing, the pans are

allowed to equilibrate for 1 hour. The pans are transferred to the equipment and an empty pan is

used as reference. The heating sequence is as follows. First heating from 15 to 150C at 3 C /

minute, cooling to 30 at 30 C/min, reheating from 30 to 150 at 3C/min and final cooling to 15C

at 30C/min. The amplitude was fixed at 2C/min and frequency 0.017Hz so that effectively, the

sample is heated continuously by 3C, immediately cooled by 2C and so on. Each run takes

nearly an hour and half. A sample of potato amylose was used as standard. The enthalpy of

gelatinisation was calculated using standard software. The results were calculated on the basis

of at least three runs. .

Since the starches were obtained from different sources and it is not always safe to rely on

reported data, the amylose contents in the starches were determined for all samples by standard

iodimetric method. This involved dissolving the starch in DMSO-Urea solution, followed by

determination of absorbance of the iodine-starch complex obtained from the solutions. The total

amylose content was determined by precipitating out the starch from the solution using alcohol

followed by re-dissolving in DMSO-urea solution .and determination of absorbance. In order to

compare with data obtained by GPC, the analysis of all samples was carried out at the Food

Science department of Uppsala university based on the standardised procedure developed there.,

Starch was debranched using -amylase followed by fractionation in a Sepharose column. For

debranching, 5 l isoamylase from Pseudomonas amyloderamosa was used and after reaction,

the enzyme was inactivated in a boiling waterbath for 5 min.. The samples were injected on a

Sepharose CL 6B column (1.6 X 70 cm. ) using 0.25 M KOH as eluent at a flow rate of 13 ml

per hour. Two ml. Fractions were collected and the elution profile was obtained by the phenol-

sulphuric acid method

The results are presented in Table. The results obtained by the MDSC method have been

compared with those obtained using iodimetry and Gel Permeation Chromatography. The starch

samples used in the study are of different origins including cereal, root and tuber and pea

starches. In addition genetically modified starches from barley, maize and potato have been

compared. So a wide range of starches has been examined. Among the cereal starches, there was

good agreement between values obtained by GPC, iodine staining and the present method. The

values obtained for CTAB were higher than those obtained on using SDS. For tuber starches,

both the surfactants gave very good results. However in case of some tuber starches, the

apparent amylose was much higher than the total amylose which is not easily explainable. The

absence of lipids may a contributing factor. On the whole, the results indicate a very good match

between the amylose contents determined by iodimetry and GPC with those obtained by the

present method. A comparison between the two surfactants do not show any major difference

though it appears that CTAB is more sensitive for low amylose samples. The length of the

hydrophobic chain is very important in deciding the complex formation. It has been found that

12 to 18 carbon chain length is optimal for complexation with amylose. Both the surfactants

have this range and the role of the hydrophilic head needs further examination. The method thus

appears quite efficient since it gives acceptable vales for a wide range. The surfactants used are

widely available. Unlike iodine staining which requires defatting to get more accurate results,

the present method does not need any such step.

3. Influence of chain length on the starch gelatinisation

The influence of chain length of the lipid used for complexation with starch on the

gelatinisation characteristics was studied using MDSC. It is well-known that for efficient

complexation a minimum chain length of the lipid or surfactant is required. Though

complexation has been reported for even 6 carbon system, the optimum length is 12 to 18. The

strength of the complex is can be gauged from the gelatinisation temperatures as well as

gelatinisation enthalpy. The higher the gelatinisation temperature the stronger will be the

complex. Similarly a higher enthalpy of gelatinisation indicates stronger complex. Earlier work

has been mainly on pure amylose and complexation was mainly studied using Glyceryl

derivatives of various fatty acids and data has often been compared with the results from

different lipids or surfactants.. It was decided that a comparison will be more relevant if the

surfactant used is same and for this purpose lysolecithin having different chain length of fatty

acid was examined. A large number of starches from different sources was examined. These

included cereal starches, root and tuber starches and genetically modified ones. Lysolecithin

having the fatty acid residues (C6:0), (C-10:0), (C-14:0) and (C-18:0) were used for the study.

A 1% solution of the surfactant was prepared in double distilled water. Starch was weighed

accurately (1-5mg) into the pans, 2 times the weight of the surfactant solution was added , the

pans were sealed and MDSC was run as described earlier. The Tonset and T end and H were

determined from the thermograph after the resolution of the graphs into reversible and

irreversible graphs. At least three runs were made for each sample.

The results are presented in tables.

N

o

Starch C-6 C-10 C-14 C-18Tons

et

Ten

d

H Tons

et

Ten

d

H Tons

et

Tend H Tons

et

Tend H

1. Cassava 51.6

60.1

11.7

63.4

76.0

11.6

65.4

77.4

10.5

64.3

76.5 8.8

- - - - - - 93.7

103.4

1.88

106.0

114..8

1.8

- - - 73.5

81.0

1.3 98.4

104.9

2.4 108.7

116.4

2.75

2. Xanthosoma 74.2

81.5

13.13

72.0

79.2

12.8

75.6

82.6

11.38

74.1

81.5 9.3

- - - - - - 92.3

101.5

2.3 105.0

115.8

3.0

- - - 72.7

79.8

1.86

98.2

103.5

2.82

108.5

116.4

3.75

3. Colocasia 76.7

80.9

11.7

77.2

85.1

11.6

79.5

86.6

9.36

79.5

86.9 12.0

- - - - - - 95.1

102.0

0.53

104.2

112.5

0.5

- - - 80.2

87.3

0.38

99.5

105.2

0.98

108.4

115.4

1.15

4. D. alata 71.2

80.3

12.9

70.3

80.0

12.3

72.2

80.6

8.72

71.5

80.2 10.6

- - - - - - 94.1

102.0

0.09

104.2

115.5

3.35

- - - 72.1

78.5

1.52

94.1

104.2

2.36

109.2

116.5

3.6

5. D.esculenta 66.1

71.1

13.13

63.2

75.2

9.18

62.4

73.0

6.5 64.9

73.3 6.6

- - - - - - 94.5

105.2

1.35

104.0

114.0

1.75

- - - 71.1

78.6

1.21

98.6

104.5

1.5 109.8

115.4

1.48

6. C.edulis 64.2

71.6

9.08

63.1

71.2

12.91

64.3

71.2

8.12

63.9

71.5 12.67

- - - - - - 92.4

103.3

3.78

104.4

116.5

4.7

- - - 73.3

78.8

1.6 98.2

104.2

2.98

110.5

117.5

3.98

7. Amorphophallus

78.0

84.8

12.26

75.1

83.0

14.48

77.9

85.0

12.16

77.15

84.3 9.38

- - - - 94.1

102.3

2.0 104.5

116.7

3.38

- - - 71.2

78.6

2.28

98.0

104.3

2.9 109.1

116.8

3.5

8. D.rot 74.5

83.1

11.8

72.1

81.9

13.2

73.3

84.7

9.65

72.4

81.3 8.45

- - - - - - 93.9

101.3

1.25

103.8

115.5

2.52

- - - 73.7

80.2

1.49

97.5

103.0

2.71

109.1

116.2

3.2

9. Pacchy. 67.0

73.1

8.83

62.6

72.9

9.47

64.4

74.5

9.45

63.7

75.3 8.10

- - - - - - 94.2

103.1

2.37

104.7

113.8

2.35

- - - 75.7

85.1

0.66

99.0

105.4

2.53

106.7

118.2

3.24

10

Arrowroot 69.1

77.3

12.31

68.8

78.0

12.61

71.3

79.5

7.85

70.2

78.6 8.37

- - - - - - 97.3

102.4

2.15

106.3

115.9

3.0

- - - 71.8

79.2

1.82

97.5

103.9

2.62

109.1

116.6

3.4

Various interesting points emerge from the results. As is evident from the table, the chain

length really influences both the gelatinisation temperatures and the enthalpy. The peaks

corresponding to starch gelatinisation, starch-lipid complex melting during first heating and

during second heating are affected. For wheat starch the values are 48-58 , 102-114, and 107-

116C for C18 lysolecithin. For C14, the corresponding values are 50-64, 93-102 and 98-

105C . When C10 is used the values are 50-59, 69-87 and 77-88C respectively. However for

C6 only peak for starch gelatinisation was observed. The following conclusions can be drawn.

There is no effect of chain length on the starch gelatinisation temperature since there is only very

small difference between the values. Increase in chain length leads to higher gelatinisation

temperatures for the starch-lipid complex melting indicating the strength increases with increase

in chain length. This is further confirmed by the results for the C6 system where there is no peak

at all for the starch-lipid complex melting. A comparison of the values for cassava starch is as

follows 64-76 for starch gelatinisation, 106-114 for starch-lipid complex melting for first

heating and 108-116C for second melting with C-18. For C-14, the values are 65-77, 92-101

and 98-103C. In case of C-10, the gelatinisation temperatures is.63-76C. Though there is no

peak corresponding to starch-lipid melting during first heating. there is a peak for melting of

starch complex. during second heating . The absence of the peak for the first heating is due to

the masking of this peak by the starch gelatinisation peak. This is confirmed by the enthalpy

values for the starch gelatinisation.

Similar results were obtained for all the tuber starches. It was also observed that there was

no peak for starch-lipid complex melting when C6:0 lysolecithin was used showing that there is

no effective complexation when the chain length is only 6 and this effect is clearer when tuber

starches are used. The peak for starch-lipid complex melting was observed only for Glacier

variety of Barley during first heating and this result with this starch can be explained on the

basis of high amylose content in this variety.

The results with the enthalpy also showed similar trends. The H values for gelatinisation

of wheat starch were 5.6 J/g for C-18, 4.95 for C-14, 6.3 for C-10 and 7.49 J/g for C-6

lysolecithin respectively. For the starch-lipid complex melting during first heating, the values

were 4.2, 3 and 2.2 J/g and those for second heating the values were 4.17,3, and 2.2 for C-18,

C-14 and C-10 respectively. It is noted that there is no peak for the starch-lipid complex melting

indicating that the complexation of lipid with C-6 system is negligible or absent. This can be

expected because minimum 6 carbon is required for complexation and the bulky hydrophilic

head may be inhibiting complex formation. The enthalpy for starch gelatinisation for C18 is

higher compared to C14 . However, for C10, the enthalpy is again higher and this is not

explainable. Similar trend is observed for the other cereal starch samples. For tuber starches,

the H showed a steady increase with reduction in chain length. Such difference between the

starches is not clear. . The H values for starch-lipid complex melting show reducing values

with reduction in chain length for most starches. However for the tuber starches, the first starch-

lipid complex melting peak is absent and hence there is no H values for these. The values for the

second peak follow clearly the trend of reduction with reducing values of chain length.

The data thus clearly indicate the following. The longer the chain length, the

complexation is stronger. This is shown by the higher gelatinisation temperature and

gelatinisation enthalpy of the starch-lipid complex melting . These show higher values during

second heating as expected proving that amylose leaches out during gelatinisation of starch.

The complexation formed with C-6 is very low or absent or even if formed, it is very weak. The

role of the hydrophilic head is also important. Some differences exist between the cereal and

tuber starches in their complexation with C-6 lysolecithin indicating differences in their internal

structures..

Effect of native lipids on the gelatinisation of different starches.

It has been observed that durum wheat provides better quality needles compared to normal

wheat flour. The reason behind this is not clear. It was felt that the native lipids present in these

may be influencing the starch gelatinisation differently, since it is basically the starch which

gives the texture, structure and shape to the needles. To examine this aspect, it was decided to

study the effect of native lipids from wheat, durum and rye on the gelatinisation characteristics

of starch of D.alata and pachyrhysus. These two root starches were taken since D alata has a

B XRD pattern and Pacchyrhysus A pattern and so the study can throw some light on the

starches with different structural properties.

The total lipids were isolated by extraction of the corresponding flour at room temperature

with ethanol and removal of the solvent in vacuum, The polar lipids were separated from the

total lipids by column chromatography. Accurately weighed quantity of The lipids (200mg) was

allowed to equilibrate with water, starch (200 mg) was added and the mixture was thoroughly

mixed to ensure uniform distribution. For DSc studies, a small quantity of the material was

accurately weighed and transferred into the pan, taking care that all the material is completely

inside the pan, it is sealed and placed into the sample holder. The DSc was run as follows

Heating 15 to 150 at 5C/, cooled to 30, reheated to 130 at 5C/min and cooled again. The

gelatinisation parameters were directly read out from the thermograph. Each sample was run at

least three times using polar lipids and total lipids.

The results are summarized in Tables. It is evident that the lipids form strong complex

with the starches examined. However the results do not show any higher value for polar lipids

compared to total lipids. It was expected that the polar lipids should form stronger complexes

and should give higher values for both gelatinisation temperatures and enthalpy . Such result

was not observed . But the results clearly showed that the tuber starches can form complexes

with lipids and there is no inhibition for such complex formation and hence lipids can be used to

modify the starch properties.

2.10. Gelatinisation and Pasting temperature

Gelatinization of starch takes place over a definite range of temperature known as

gelatinization temperature. Gelatinisation temperature can be measured microscopically, by

DSC and also by using a viscograph. However use of viscograph provides the pasting

temperature rather than gelatinisation temperature. The former may be defined as the

temperature at which a perceptible increase in viscosity occurs and is always higher than

gelatinisation temperature. Among different tuber starches, cassava starch has the lowest

gelatinisation temperatures. No relationship between granule size and gelatinization

temperature was observed [29]. Pasting temperature of H-165 starch determined using a

viscograph was slightly lower than those for most of the other varieties, and M4 starch had the

highest range of pasting temperature [15]. These values are quite close to DSC values of 66

and 78°C for Tonset and Tpeak respectively. When cassava starch was subjected to steam

pressure treatment at different pressures, there was progressive increase in pasting temperature

by 2 to 9° C depending on the time of treatment and pressure used. The pasting temperature rise

was higher for longer time of treatment and higher pressures [39]. Increase in pasting

temperatures was also observed on treating the starch with surfactants [17]. It was found that

different types of surfactants generally increased the pasting temperatures, but most pronounced

effect was noticed on treatment with potassium palmitate and potassium stearate. On

esterification to acetate, the pasting temperatures were reduced due to weakening of associative

forces [40]. Examination of gelatinization temperature of cassava starch in non-aqueous

solvents indicated that the values were enhanced tremendously in glycerol and ethanol, while in

DMSO and formalin, only slight increase was noticed. The large increase in the first two

solvents can be traced to steric factors [41].

The pasting temperature of sweet potato starch varied between 66.0 to 86.3°C °C. .

Pasting temperatures of different cultivars of Colocasia esculenta and Xanthosoma

sagittifolium starches have been determined using the Brabender Viscoamylograph.. There was

only very slight difference between varieties but the pasting temperatures of these two

starches were distinctly higher than those of cassava and sweet potato starches. The

gelatinisation temperature of starch of three accessions of Canna edulis was 74-85 to 80-95°C

by the Brabender Amylograph, but 74-75°C by the RVA [26]. Pasting temperatures of starch of

Amorphophallus paeonifolius extracted from 10 accessions were compared and again no

significant variability was noticed and the starch gelatinised in the same range as the other aroid

starches viz. ., 81-85 to 82-85°C [31] However the range was lower compared to cassava or

the yam starches. For Pacchyrrhizus starch, we obtained values of 74-79°C and only minor

variation existed among varieties [3]. The values for curcuma starch was 81°C by RVA [27]

while it was 65-85°C for coleus starch determined microscopically[16]. Yam starches generally gelatinised over a temperature range of around 20°C and

gelatinisation continued even after 95°C showing strong intermolecular linkages. The large range

for yam starches may be attributed to the presence of phosphate linkages in these starches (similar to

potato starch) since it was found that the yam starches invariably contained higher quantity of

phosphorus.

2.11. Viscosity

An important and useful property of starch is that it provides a viscous paste when heated in

presence of water. It is this viscosity that accounts for the use of starch in textile, paper, adhesive

and food industries.

4. Detailed Brabender viscographic studies on cassava starch from different varieties and

at different starch concentrations have been carried out and the results indicate variation

in the viscosity parameters. There was no correlation between viscosity and granule

size. peak viscosity and setback viscosity. .

In a Redwood Viscometer No. 1, a 2% paste of cassava starch had a

value over 50 seconds and only minor variation among varieties was

observed. When cassava starch was subjected to steam pressure

treatment, the viscosity fell steadily with increase in pressure and time

of treatment. At a pressure of 15 psi for 150 minutes, the viscosity fell

from 58.5 seconds to 30 seconds. The same trend was observed in the

Brabender Viscosity results also, where the peak viscosity dropped from

430 BU to just 30 BU. It was also observed that the reduction in

viscosity was linearly related to the severity of treatment. [39]. .

It was observed that different surfactants affected the viscosity of cassava starch

differently [17]. Whereas sodium lauryl sulphate increased the peak viscosity, especially at

higher concentrations, the effect of potassium stearate and potassium palmitate was not so

pronounced. Glyceryl monostearate was found to reduce the peak viscosity at higher

concentrations. Similar effect was observed for the Redwood 2% viscosity values also.

Viscosity of cassava starch in various non-aqueous solvents has been compared [41].

Ethanediol depressed the Redwood viscosity from 55 seconds to 17.5 seconds, while glycerol

increased it to 175 seconds. DMSO and Formalin also increased the viscosity, but to a much

lower extent.

In addition to peak viscosity, the breakdown in viscosity is another important criterion

that decides the applicability of starch in food and industry. In this respect, cassava starch is

considered inferior to maize starch, because its viscosity is rapidly reduced on heating under

shear leading to a ‘long’ and cohesive texture for its paste, which is not desirable in food and

textile applications. Much effort has been paid to strengthen the starch paste viscosity. Steam

pressure treatment can improve the paste stability, but it is accompanied by a corresponding

reduction in peak viscosity. However, surfactants were found to have a more desirable effect.

On incorporation of potassium stearate or potassium palmitate, even at 0.02% mole

concentration/100 g starch, the viscosity was maintained and also stabilised [17]. Since the

surfactants are easily handled and work up is easier the method may be used to modify starch

viscosity.

In view of the presence of a large number of hydroxyl groups in

starch, cross linking has been used to stabilise starch viscosity. Various di-

and tri-functional chemicals have been used to crosslink the starch. The

most effective chemicals have been epichlorhydrin, phosphorus oxychloride

and sodium metaphosphate. These chemicals bind the starch molecules in

the granules, increasing the associative forces, rendering the starch

granules stronger and preventing breakdown during heating and stirring

The textural properties of cassava flour could be improved by treatment with

phosphoric acid and > however the latter imparted a bitter taste to the

product.[42]. . Recently, it has been found that some Lewis acids are able

to liquefy starch at low concentrations of the salt without affecting the basic

properties of the starch and this treatment may be effective as a method for

thinning starch. Many salts can influence starch properties depending on

the type of salt used [44,45].

Whereas a large amount of work has been done with cassava starch, only

very little work has been carried out on the other tuber starches. Sweet

potato starch behaves almost similar to cassava starch in its viscosity

characters, viz., peak viscosity, viscosity breakdown and setback

viscosity. The rheological properties of sweet potato starch extracted

using an enzymatic process did not vary among the different

concentrations of enzyme used upto 0.1% [9]. Breakdown in viscosity

was observed only at higher concentration of enzyme The rheological

properties of various tuber starches have been compared using the Bohlin

rheometer and wide variability in the values of G’ and G’’ was observed.

However all the starches exhibited uniformity in their elastic behaviour

predominating over viscous nature , Table 12, Fig. 9[47].

Data on the viscosity characteristics of the other starches are also widely variable .

The viscosity of Colocasia starch extracted from ten cultivars was less than that of cassava

starch and close to cereal starches . Considerable difference in peak viscosity values among

the accessions was observed. . At 5% concentration, the viscosity ranged from 130 to 350 BU.

The lowest and highest values at 6% and 7% concentrations were 200 and 600 (6%) and 320

and 880 BU (7%) respectively [24]. It was also interesting to observe that C-9 starch having

the highest granule size and amylose content had the highest peak viscosity. As earlier stated,

there was only nominal breakdown in viscosity even at the highest concentrations pointing out

the possibility of using this starch in various applications which require paste stability.. The

viscosity values were nearly same for the corm and cormel starches [30].

Variability in the viscosity properties of Amorphophallus paeoniifolius starch extracted

from ten accessions was quite minor [31]. The values ranged from 280-380 BU at 5%

concentration, 450-620BU at 6% concentration and 770-920 BU at 7% concentration. The

viscosity breakdown for the starch samples was very low, similar to other aroid starches and in

the same range as the cereal starches

Starch extracted from seven varieties of Xanthosoma sagittifolium has been compared

for its viscosity. There was only a slight difference in the viscosity values among the varieties.

The highest value was 360 BU and the lowest 280 BU at 6% concentration. The breakdown

varied from 0 to 30 BU at 7% concentration, showing the stability of the starch paste.

All the yam starches showed a characteristic pattern of slow rise in

viscosity and even after 95°C an increase in viscosity was noticed. This

implies that all the granules do not gelatinise at 95°C and some of them

gelatinise only during the holding period. In this respect the yam

starches resemble potato starch.

The viscosities of starch of four varieties of D. esculenta extracted using water and

ammonia solution were compared. There was only minor difference in the values between the

varieties (800-950 BU), but the viscosities of starch extracted using ammonia solution were

much higher than those obtained by water extraction.

When the viscosity of D.alata starch from five varieties extracted with water and

ammonia was compared, the results were not so conclusive. Mostly, there were no peak

viscosity values. As observed for the D.esculenta starch, there was no observable breakdown

in viscosity on heating and stirring.

The 2% viscosity of six varieties of D. rotundata starch varied from 37.5 to 46

seconds . As far as the paste viscosity is concerned, the values ranged from 325 to 550 BU at

5% concentration and 680 to 920 at 6% concentration [25]. The viscosity breakdown was

quite low in spite of the high viscosity levels. The yam starches contain three to four times as

much phosphorus as found in cassava and aroid starches. It has been reported that the

phosphate linkages in potato starch is responsible for its high viscosity and such effects may

also be important in the yam starches. Steam pressure treatment of the D.alata and

D.rotundata starch has been found to reduce the viscosity. The reduction in viscosity was

found to be directly related to the pressure and time of treatment (Fig. 10). The peak viscosity

came down to nil value at 15 psi for 60 minutes for both the starches [34]. This method can be

tried as a method for modification of starch, since the process is simple and does not involve

use of any chemicals and so workup is simple The Redwood viscosity of Coleus starch

was found to be 37 seconds at 75°C for a 2% solution which increased to 56 seconds on

cooling to room temperature [16].

5. Rapid Visco Analyser has become more popular in studying viscosity and many publications

have come out recently on the studies on tuber starches . . The RVA profiles starch

of some varieties of D. alata, D.esculenta and D. rotundata harvested at different maturity

have revealed that maturity did not affect the rheological properties to any major extent.

Pacchyrrhizus starch had similar viscosity as arrowroot and there was only very little

difference among 10 varieties examined. . Results in our laboratory, however do not show

such high setback for Canna starch. The peak viscosity values for the starches from three

accessions of canna varied from 3887 to 4187 cPs. The RVA patterns of the starches from

the three accessions do not coincide exactly with the Brabender data . The results indicate

noticeable breakdown for all the three starches but is not widely different among them [26].

Viscosity studies on Curcuma starch showed that variation exists between the two species

studied. and removal of curcumin lead to an increase in peak viscosity of C. zedoaria starch

almost to the level of C. malabarica starch . The breakdown in viscosity was quite low

showing that the granules are quite strong and resist breakdown under shear and heat. In this

respect also, it resembles yam starches rather than cassava,

6. Rheological studies on tuber starches

Rheological studies of the starches extracted from Amorphophalus, Xanthosoma, Colocasia,

D.rotundata, D.alata and D. esculenta tubers treted with selected concentrations of SHMP,

NaCl, KMS, GMS and NH4OH and control starches were conducted in a Bohlin rheometer

system (oscillation set). The experimental conditions were:

a. torque element 1.542gcm.

b. Measurement interval - 60s.

c. Thermal eqlbm. Time - 10s.

d. Sensitivity - 1%

e. Amplitude - 3%

e. Heating rate -1.5 C/min

Auto strain off.

The cup in which the starch slurry had been poured into was a C25 measuring system.

Frequency, phase angle, viscosity, storage modules(G‘) loss modules (G’’), range , strain and

correlation were determined at each one minute time interval. The ratio G’/G’’ was calculated

a t 95C 75 C, 60 C, 45C and at 35C at different time intervals.

From the date obtained, the rheological properties of different starches were examined.

In the case of D.rotundata tuber starches, GMS treated starch had grater G’ value and

G’/G’’ ratio compared to other treatments. This indicates a greater elastic behavior of the

starch. For all the treatments and control G’ and G’’ are maximum at 95° C. Thereafter,

they decrease and on cooling beyond 35°C, G’ and G’/G’’ values increase. That is the elastic

behavior is gradually decreasing upto 35° C and then an increase in elastic property takes place

For control D. alata starch, the G’ value ranges from 105 Pa to 90.4 Pa and G’/G’’ value from

11.4 to 6.41. SHMP, NaCl, KMS and NH4OH treated starches have lower G’/G’’ and G’’

values compared to that of control starches. But all the chemically pretreated starches showed

similar trend in the G’ and G’/G’’ changes. D. alata control starches have lesser G’ values

than D.rotundata starches at higher temperature. Hence these starches possess more elastic

properties than D .rotundata. at higher temperature. But at 35°C, after 45 minutes the values

were higher for D.alata starch. The G’ values were lowest for NH4OH treated starches and the

highest for SHMP treated starches. The G’ values of control sample ranged from 59 to 146 Pa.

G’ value decrease up to 45 C and there after increases on cooling. That is liquid characteristics

were more significant at higher temperature while at lower temperature the elastic (solid)

characteristics become more prominent.

G’ values of the D. esculenta control starch ranged from 19 to 25.3 Pa. The value decrease

upto 60°C and thereafter increased and on cooling to 35°C the values remain constant. All

chemically pretreated starches behaved in a similar manner as that of the control. SHMP treated

starches had the highest G’ value but the ratio of G’/G’’ value was highest for GMS treated

starches.

Amorphophallus tuber starches possess almost same G’/G’’values at different temperatures. A

small decrease in the G’/G’’ ratio was observed upto 35°C and thereafter an increase was

noticed.. The G’/G’’ value were found to be highest foe GMS treated starches.

Colocasia tuber starch had higher G’/G’’ values in the range of 1.4 to 6.8. G’ values

increased when the temperature was decreased from 95 C to 35 C. Hence the elastic behavior

was more prominent at lower temperature for Colocasia starch. NaCl ,GMS and KMS treated

starches behaved in a similar manner as that of the control samples but cooling after 35 °C did

not make any significant change in G’/G’’. The G’’/G’’ were higher for GMS treatment than

control.

In case of Xanthosoma control starches. G’/G’’ value decreased after 45 C and increased on

further cooling. But all the chemically treated starches showed decrease in G’/G’’ upto 60 C

and thereafter increase with decreased temperature. At higher temperatures GMS treatment

provided the highest G’/G’’ value. But on cooling at 35°C for 60 minutes, G’/G’’ values were

more or less similar for GMS and KMS treated starches.

Thus it is clear that different pretreatments bring about different effects on rheological

properties. However the results indicate that the treatments do not bring about any major

changes in the elastic characteristics of the starches and hence the treatments do not bring about

any deleterious effect on the starch properties.

A comparative study of different tuber starches was made using the Bohlin rheometrer.

Three concentrations were examined viz. 3,4 and 5%. From the data, three factors were

compared including viscosity, elastic modulus and phase angle. The results indicated wide

variability in these among the different starches

The viscosity data obtained from the rheograms do not yield any conclusive results. For

most of the starches, no clear trends could be observed except that increase in concentration led

to increase in viscosity, but the increase was not quantitative. However, the difference in the

viscosity among the starches was obvious. Canna edulis and D rotundata starches had higher

levels of viscosity at all the three concentrations while Colocasia and D. esculenta had low

values. The aroid starches appear to provide more reliable results compared to the yam

starches There is good agreement with the Brabender results that Canna edulis , D.

rotundata and D. alata starches possess high viscosity while Colocasia and Xanthosoma have

low viscosity levels. Breakdown in the viscosity and setback observed with the Brabender

viscographs are not very evident. The results are presented in Figs.1

Storage modulus

The storage modules (G’) for the different starches at the three concentration are given

in Figs. Wide variation between the different root starches could be observed. The range of

values for Xanthosoma starch at 3% concentration was 0.1 to 0.2 Pa during the heating-cooling

cycle; which increased to 5-7 Pa at 4% and 12-33 Pa for 5% starch concentration. During

cooling, a slight decrease was observed for 3% concentration. The results indicate low gel

strength at this concentration. At 4%, the increase in G’ during cooling was more apparent and

this became more significant at 5%, showing high gel strength at 5% concentration.

For D. alata, the G’ values were quite high especially at higher concentrations. The

range at 3% was 6-12.6 Pa . There was a small increase during holding at constant temperature

(95°) and cooling to 35°C. At 4% concentration, the values were much higher (36-53 Pa) with

a small increase during cooling and holding at 35°C but was not very significant. But at 5% ,

the increase during later stage was very evident. Earlier experience on this starch had shown

that the starch has a good gel strength and is confirmed by the present study especially at higher

concentration.

For Pacchyrrhizus starch, the G’ was quite low at 3% during heating and till last stages

of cooling, when there was a noticeable increase. At 4% concentration, a discrepancy was

evident during initial phase, but the increase in cooling was obvious. This was further

confirmed by the large increase in 5%, The results indicate strong elastic nature and gel

strength for the starch at high concentration.

Colocasia starch had very low G’ at 3% and hence very low elastic character. When

concentration was increased to 4% the values were much more perceptible and there was a

sharp increase during cooling . For 5% concentration the G’ was nearly 30 times that at 3%

and increase on cooling was very evident. Thus elastic character becomes clear at 5% and

though the gel strength was not high , tendency to gel was obvious. Colocasia starch has been

found to exhibit low viscosity and relatively poor gel strength (Moorthy, 1994). These

characteristics may be related to the small granule size of this starch.

Arrowroot starch at 3% concentration had a detectable G’ at 3% concentration, which

increased with concentration, two fold at 4% and three fold at 5% concentration. The storage

modulus followed the same pattern as the viscosity, a fall during holding at 95°C , than a

slight increase on cooling and then remaining steady. This was true for all the three

concentrations and the increase was nearly same at these concentrations.

For cassava starch, the trends were clear. At 3%, the values were insignificant, but at

4% , they became evident (5-7) while at 5% they were much more significant. . However at

5%, there was a steep fall during holding period and then a small rise, very similar to arrowroot

starch. In this respect G’ resembled viscosity pattern at 5% concentration. The rapid fall at 5%

concentration during heating and holding reflects the breakdown of the starch which is also

evident in the Brabender Viscograph. Though the starch exhibits good elasticity , the gel

strength doesn’t appear to be very high on cooling.

D. esculenta starch had very low G’ at 3% Even at 4%, the G’ was low, but during cooling

some increase was evident. At 5%, the G’ was quite detectable and showed a rapid raise

during cooling. No further change was observed. The viscosity results also had shown a

similar trend. D. esculenta starch has very small granules and thus similar to Colocasia

starch. For these starches swelling is also not very high and hence the observed low values for

viscosity and G’

Canna starch has been found to possess very high gel strength both in the

Brabender Viscographic measurements and also during preparation of

various food products This was confirmed by the G’ data in the present

study . At 3% concentration itself, the values were highest during the

starches examined (10-22 Pa). At 4% the increase was two fold which

further rose 10 fold at 5% concentration. Though there was a tendency to

increase during cooling, it was not very high. The starch thus possess high

elasticity and gel strength and can be useful in many food applications.

Canna starch is known to possess high phosphorus content and perhaps

this helps in its possessing high G’ and gel strength.

D. rotundata starch, was similar to canna starch in having high G’ .

At 3%, the value was 10-35 Pa increasing to 20-35 for 4% and further to

45-65 Pa for 5% concentration . D. rotundata starch has also been

found to be possess high gel strength and elasticity and is confirmed by

the present results . However a fall during cooling is difficult to explain

and may be due to experimental error.

For Amorphophallus starch trends were more evident . The G’

values were 1.4-3.5 Pa for 3%, increasing to 8-10 for 4% and further to

14-23 Pa at 5% concentration. There was also an increase during latter

phase of cooling. This indicates that the starch has higher elasticity

compared to the –other aroid starches.

The results on storage modules indicate that Canna edulis and

D.rotundata starches possess high elasticity and gel strength. The aroid starches have lower

G’ , but definite trends could be observed for these starches. A 6.4% paste of sweet potato has a

reported value of over 150 Pa at 85° falling to less than 100 Pa on further heating and then

cooling. The values appear quite high compared to the starches used in the present study even

taking into account the higher concentrations used (Garcia et al, 1998). 4%cassava paste has

been found to have a G’’ value of 16.57 Pa at 20° after cooling. (Hansen et al, 1991)

Phase angle

The phase angle change due to shear gives an indication of the

strength of the starch gel. It reflects the ratio of elasticity to viscosity of

the samples.

Figs. provide the trend of the different starches. The phase angle values for Xanthosoma starch werein agreement with the G’ values. At 3%, the phase angle values were in the range 27-65 whichdropped to 12-20 at 4% and 2-24 for 5% concentration. There was a steep fall at the initial stage ofheating at 3%, which may be due to very low values for G’ at this stage . For 4% concentrationalso, there was a small increase in phase angle during cooling, which is not explainable. However at5%, the behaviour was as expected and there was a steady decrease during cooling and thenremained steady

For D. alata starch, the data was rather irregular and though the trend indicated

a decline with increase in concentration, the data was not in consistency with G’ values. G”

though low, may also be influencing the deformability of the starch paste.

Pacchyrrhyzus starch exhibited definite trend of a reduction with increase

in concentration. Lowest phase angle of 13-28 was observed for 5%

concentration as expected. Compared to other starches, the values are quite

high and in conformity with G’ values. Though the starch does not possess

high elasticity, the phase angles were on the higher side.

The data for Colocasia starch was quite inconsistent at 3%, but for 4% and 5%

the values were more reliable and as expected there was a reduction with increase in

concentration. However there was no decrease in the values on cooling, -indicating that gel

strength does not increase with cooling.

The values for phase angles were nearly same at 3, 4 and 5%

concentrations for arrowroot starch. Though G’ increased steadily with

concentration, the phase angles were nearly equal . The range was 16-70

or 3%, decreasing to 14-48 at 5% and there was no decrease in the phase

angle values during cooling showing poor gelling tendency.

Cassava starch had a phase angle values of 38- at 3% which fell to 10-25

at 5% concentration . The high value at 3% is due to the low G’ at this

concentration. The values were nearly same at 4 and 5% concentration.

Cassava starch thus appears to achieve high elasticity at 4 and 5%. The gel

strength cannot be considered very high but still large.

For D. esculenta starch, the values were very low at 3% concentration but at

4 and 5% levels, the values were in line with G’ values. At 5%

concentration, a high gel strength is indicated by low value for phase angle.

Though G’ had risen very rapidly at later stages, this effect was not visible

in the phase angle values.

Canna edulis starch had exhibited high G’ at 4 and 5% concentration, but the

phase angle values do not reflect the same effect. Though there was a progressive decrease with

increase in concentration, it was not following a definite relation. Even at 3% concentration,

the values were quite low indicating high elastic nature of the starch paste.

For D rotundata starch, the values were quite low even at 3% concentration

showing high elasticity , but at 5% concentration, the values did not reflect the high G’ observed.

Generally high gel strength was noticed for this starch.

For amorphophallus starch, the results do not show any special trend, 5%

values being lower than 3 and 4% values. There was no decreasing trend on

cooling. In contrast to G’ which showed high values, the effect was less

prominent.

Strain sweep tests

The results of the strain sweep experiments are presented in the

figures. The following trends emerged . Higher the G’, the greater is the

tendency to breakdown under shear. This was found to be true for all high

G’ starches, viz., D. rotundata, D. alata and Canna edulis. For medium G’

starches the thinning was evident at the highest concentration, while it was

quite negligible for the low G’ starches. Amorphophallus starch however did

not show such tendency. Even among the different concentrations, the

same effect is very clear. At higher concentrations, the intermolecular

collisions will be more and this can lead to breakdown in the G’. In addition

for Colocasia and D. esculenta starches, their smaller granular size may also

be contributing to the stability.

The summary of results is presented in Table 2. The highest viscosity values

were observed for Canna edulis, followed by D.alata and D.rotundata. Colocasia ,

Pcchyrrhyzus and Xanthosoma starches had low values. Cassava starch also exhibited

unexpected low values. The general tendency of increase with concentration increase was

evident. The storage modules also followed the same trend, with Canna edulis having high

storage modulus and in line with Brabender viscosity values and the observed gel strength of

their pastes. Cassava starch has Arrowroot had reasonable high values at 5%,

while also exhibited high values at 5% concentration. The values were nearly low for

colocasia, D. esculenta and Pachyrrhyzus . Starches. The trends were quite clear for Viscosity

values for Amorphophallus, Cassava, Arrowroot and Canna starches. For Colocasia and

D.esculenta starches, the values were prominent only at 5%. Most of the increase was found

during cooling.

For storage modulus, trends were quite evident for Canna, arrowroot,

Amorphophallus, Colocasia and Pachyrrhyzus starches. Only D. alata exhibited variation.

Colocasia and Xanthosoma starches had higher G’ during cooling, while these were less for

most of the other starches which showed almost equal values. The high gel strength of C.

edulis, D.esculenta, and D.rotundata starches is evident from the values.

The phase angle values also follow the pattern of G’. Though most of the

starches showed a decreasing trend during cooling, it was not observed for

all starches.

Thus the results clearly point out that viscosity measured by the Bohlin

rheometer is not very reliable at low concentrations and also for starches

which gelatinise slowly beyond 95°C . It may not be correct to compare the

Brabender values with the Bohlin data. The G’ values are consistent with

the gelatinisation profile for most of the starches and most of the starches

show elastic characteristics especially at higher concentration. The phase

angles do not follow the same trend as G’ indicating that the effect of

variation in loss modulus (G”) may be important in many cases.

2.12. Swelling power and solubility

Starch swells on heating in water and the extent of swelling depends on the origin of the

starch. Swelling power and solubility provide evidence of non covalent bonding between starch

molecules. Factors like amylose-amylopectin ratio, chain length and molecular weight

distribution , degree / length of branching and conformation decide the swelling and solubility

[20, 48]. Cassava starch has swelling power which is in between those of potato and cereal

starches- a property in conformity with its observed viscosity. The swelling volume of different

varieties of cassava varied from 25.5 to 41. 8 ml g-1 of starch (Tab. 13). during the growth

period , starch of two varieties H-2304 and M4 maintained their swelling volumes within small

ranges, while that for some varieties such as H-165 expressed wide variations which indicate

that these varieties are very much susceptible to environmental influences [23] Fig 11.

Swelling volumes also depend on the presence of various chemicals and any treatments carried

out on starch. A high amylose content and presence of stronger or greater numbers of

intermolecular bonds can reduce swelling . Formation of lipid-starch complex can also affect

the swelling volumes as also presence of naturally occurring carbohydrate and

noncarbohydrates along with starch [20]. This has been amply illustrated in the effect of fibre on

the swelling volumes of different varieties. The fibre acts as barrier to free swelling of starch. It

was also found that extraction with ethanol or defatting of flour did not change the swelling

volumes showing that the suppressive effect is more due to the fibrous material rather than lipid

or sugars present in the flour [15]. The starchy flour extracted from fermented tubers also

exhibited the same trend [49]. Sodium sulphite was found to have noticeable effect in

suppressing the swelling volume of cassava starch. The swelling volume dropped to very low

values at definite concentrations The values dropped nearly to zero at 0.05 and 0.1%

concentration of the salt (Fig 13). At higher concentrations, the swelling volumes increased to

nearly the same level as the native starch. The effect has been attributed to the oxidative-

reductive depolymerisation brought about by the sulphite ions. The effect was nullified at higher

concentrations due to destruction of the sulphite ions. Similarly the effect of the sulphite was

neutralised by addition of propyl gallate which is an oxygen scavenger [43] . The effect was not

unique to cassava starch and swelling volume of Dioscorea starches was lowered by sulphite at

similar concentrations also. Thus the effect can be attributed to the salt. In order to check

whether is effect is only with sodium sulphite alone, other salts were tried including potassium

sulphite, sodium chloride, sodium sulphate and sodium phosphate. Potassium sulphite gave

similar results showing that the suppressive effect is due to sulphite ions while other salts failed

to produce such a trend. Another salt that brought about a similar effect was sodium

thiosulphate at the same concentrations. [50]. The swelling vlomes were lowered at 0.01% and

then increased. The solubility on the other hand experienced a drastic increase at the same

concentration and this salt also be acting similar to sodium sulphite. Surfactants also affect the

swelling volume of starches. The swelling volume was reduced by half by potassium palmitate

and potassium stearate even at lowest concentrations, while glyceryl monostearate affected

only to a small extent. In contrast sodium lauryl sulphate and cetyl trimethyl ammonium

bromide enhanced the swelling volume considerably [17]. . Steam pressure treatment also

lowered the swelling volume by compressing the starch molecules and thus restricting the free

swelling of starch [39]. Considerable variation in swelling volume of different varieties of Colocasia was

noticed. The values ranged from 26.5 to 60 ml g-1 – which indicates a high degree of variability.

For C-9 starch, having highest granule size, the swelling volume was the least [24]. Inverse

relationship was noticed between the granule size and swelling volume of ten accessions of taro [30].

Swelling volume of starch of six clonal selections of D. rotundata has also been

examined at different concentrations and only slight differences were noticed among the

selections. At 1% concentration the values ranged from 15-25 ml g-1 and at 5% , the range fell

considerably due to deficiency of enough water to swell all granules [25]. Starch from different

varieties of D. esculenta, D. alata, Xanthosoma sagittifolium and Amorphophallus

paeoniifolius had much lower ranges . The relatively lower swelling of Dioscorea starch

compared to potato starch has been attributed to the higher lipid content in the starch and also

higher inter-associative forces compared to potato starch. Swelling volume of Canna edulis

starch was observed to be 11-14 ml g-1 for three accessions of canna starch. In general, the

aroid starches had rather low swelling volumes. Starch from ten accessions of A. peoniifolius

had swelling volumes ranging from 11.7 –13.0 ml g-1 at 0.5% concentration and 21.5 to 24.4

ml g-1 at 1.0% concentration [31] . For Coleus starch, the swelling volume was around 25

ml g-1 [16]. For Curcuma starch, the value obtained was 19 ml g-1 for C. zeodoria and 30 ml g-1

for C. malabaricum starches [27]. The swelling volume of starch from Amorphophallus

extracted from pretreated tubers with different chemicals depended on the chemicals used. All

the chemicals lowered the swelling volume, but highest reduction was with Glyceryl

monostearate. [8]. For Xanthosoma starch, Glycerol monostearate (GMS) and ammonia

enhanced the swelling volumes to a small extent [33].

Solubility of starch also varies with origin of starch. Solubility depends on a number of

factors like inter-associative forces, swelling power, presence of other components etc. Cassava

starch has a higher solubility compared to the other tuber crops and the higher solubility can be

attributed partly to the high swelling it undergoes during gelatinisation. The solubility values

ranged from 25 to 48% . The solubility of starch of different cassava varieties varied from 17.2 to

27.2%. However no direct correlation between swelling and solubility could be observed [3].

Solubility data of starch from different varieties during the growth periods also showed that starch of

varieties H.2304 and M4 had good stability in their solubility, whereas the others had medium or

poor stability [23]. The solubility was enhanced by heat moisture treatment.

Solubility of cassava starch in various non-aqueous solvents has been examined. It was

found that maximum solubility was obtained in DMSO and formalin, while in glycerol it was

moderate. Starch was insoluble in anisole and methyl cellosolve (Tab.14). The solubility data

indicate that starch is more soluble in polar solvents or solvents with affinity towards water [41].

The solubility of starch of yams and aroids pretreated with various chemicals was affected to

different extent by the chemicals used and also the concentration [8]. The values were between 18-

32%. Solubility of the other tuber starches varied from 10-30% and the aroids had usually lower

solubilities.

2.13. Clarity and Sol stability

Transparency of starch paste varies tremendously among the different starches. . The

high clarity has much relevance in food and textile applications. Clarity depends on the

associative bonds between the starch molecules in the granules. Cassava starch, having weaker

associative forces compared to cereal starches has thus better clarity. When derivatives of

cassava starch were compared, acetylated and propylated derivatives had better clarity , though

only to a small extent. The clarity was best when pyridine-acetic anhydride was used for

acetylation. This reagent gives highest clarity probably due to the high D.S achieved. .

Esterification tends to weaken the associative forces by reducing the available hydroxyl groups

[40]. In contrast, heat moisture treatment reduced the clarity by strengthening the associative

forces.

Dioscorea starches have almost equal clarity as cassava starch, indicating that their

associative forces are similar. Variation was not observed among different varieties of

Dioscorea alata, D. esculenta and D. rotundata starches. Steam pressure treatment was found

to decrease the clarity of D. alata and D. rotundata starches and the reduction was directly

proportional to the pressure used and time of treatment. The reduction in clarity on pressure

treatment can be attributed to the strengthening of associative forces [34] The clarity of aroid

starches is, as expected, poor and the values are closer to that of cereal starches. The clarity of

starch pastes of ten accessions of Colocasia esculenta was nearly equal [24]. Similarly no

significant variation among starch of ten different accessions of Amorphophallus paeoniifolius

was observed [31]. The clarity of three accessions of Canna edulis was found to be much

higher than the aroid starches. [26]. Generally the ‘B’ starches appear to have higher clarity

compared to ‘A’ starches.

Sol stability or paste stability reflects the retrogradation tendency of starch pastes.

Cassava and sweet potato starches have low retrogradation tendency and therefore high paste

stability. The lower retrogradation tendency of cassava may be due to the higher weight-

average molecular weight of the amylose fraction in cassava . Dioscorea starches also have

good stability, while the aroid starches have poor stability [3]. The results also reflect the

differences in associative forces among the different tuber starches.

The sol stability of cassava starch in various non-aqueous solvents has been studied.

The values varied from 3 hours in ethanediol to over 20 days in formalin. Formalin may be

preventing parallel association of the starch molecules, especially the amylose chains, by

forming some complexes [41]. Sol stability was also affected by added surfactants. Sol stability

was enhanced by derivatisation also, though there was no correlation between degree of

substitution and sol stability. The paste stability of starch of different varieties of D. alata , D.

rotundata , D. esculenta, X. sagittifolium, and A. paeoniifolius was nearly same. Heat-

moisture treatment (steam pressure treatment) of Dioscorea starches decreased the paste stability

and the observed reduction at higher levels of treatment was so high that the starch gel started

settling within 2-3 hours, indicating that the starch molecules come so close to each other by the

compressive treatment that they associate themselves very easily leading to fast settling [34].

2.14. Digestibility

Digestibility of starch by enzymes is of importance for evaluating nutritive value and

also in industrial applications. Cassava starch is one of the least resistant root starches . In

vivo digestibility of different tuber starches was studied on albino . The results indicated that in

case of raw starch, digestibility of cassava, sweet potato, Colocasia, Xanthosoma and

Amorphophallus starches was quite high (65-75%), comparable to corn starch (76%) but that of

the Dioscorea was low (15-25%) similar to potato (10%) . On cooking, the digestibility was

substantially increased for all the starches including yam and potato starches. The large

increase in digestibility on cooking can be attributed to the change in starch structure on

gelatinisation [51]. This was confirmed by the observation that the XRD patterns of all the

cooked starches were similar, unlike the uncooked starch in which aroid starches have ‘A’

pattern, and yams posses ‘B’ pattern. A comparison of the digestibility was also carried out

using pancreatic -amylase under in vitro conditions. Under in vitro conditions, maximum

activity was obtained on cassava starch while Colocasia suffered breakdown to much lower

extent indicating that in vivo and in vitro digestibility cannot be directly compared. The

digestibility could not be related either to the amylose content or the soluble amylose contents in

these starches. Earlier reports had indicated that popping of sweet potato improved starch

availability and nitrogen digestibility. . In a study of digestion of aroid and yam starches, effect

of pre-treatment influenced -amylase digestibility [33].

.

The results are summarized in Tables. It is evident that the lipids form strong complex

with the starches examined. However the results do not show any higher value for polar lipids

compared to total lipids. It was expected that the polar lipids should form stronger complexes

and should give higher values for both gelatinisation temperatures and enthalpy . Such result

was not observed and it is presumed that more experiments should be conducted to verify this.

There does not appear to be any distinct results for any of the starches examined. All this

warrant further work in this area.

The cereal starches have intrinsic lipids present on them. It was desired to find out if

added lipases modify the gelatinisation characteristics of starches. It is wellknown that these

lipids affect the starch gelatinisation to a large extent. The removal of lipids may also be helpful

in reducing the lipid flavour associated with cereal starches. Wheat starch was used for the

study. Lipase at three different concentrations (viz 1,3 and 5%) was added to a starch suspension

in water (1:1) and the pans incubated at 37C for , 15, 30, 45 and 60 min and DSC run at the

following conditions. First heating 15-150 at 5C/min, second heating upto 130 at the same

rate. The Gelatinisation temperatures and gelatinisation enthalpy starch-lipid complex melting

temperatures and enthalpy were calculated using inbuilt software. The results do not indicate

any major change in the starch gelatinisation temperatures or enthalpy for any of the

concentrations examined. However some slight increase in starch-complex melting enthalpy was

observed at 3% concentration of the enzyme for 30 minute treatment.. There was also

corresponding decrease in the temperature of melting. It is not clear why the values again tend to

change at higher period of treatment. It was expected that the lipase would act upon the native

lipids present in the starch and weaken the complex and hence reduce the enthalpy of melting.

But such a phenomenon does not happen and may be the lipase is unable to break the starch-

lipid complex. Further work using higher levels of lipase and longer

15. Conclusions

The studies on the different tuber crops reveal the vast variability available among them.

Such differences are not observed in case of cereal starches . The high viscosity of cassava and

Canna starches makes these starches very useful in many food and industrial applications especially

where high thickening power is desired. The low viscosity of aroid starches can be exploited in

paper industries which prefer lower viscosity and good film forming capacity. The small granular

size of Colocasia and D. esculenta starches make these ideal as filler in biodegradable plastics, and

in aerosols and talcum powders. The clarity of cassava, Canna and yam starches can be very useful

in many food applications. Similarly the good gel strength of these starches, especially Canna starch

can be utilised in a wide array of food products. The easy gelatinisation of cassava and sweet potato

starches can make them suitable in manufacture of hydrolytic products derived from starch . The

range of characters observed makes the tuber starches amenable to different applications based on

their properties in place of chemically modified starches. An awareness of their potential uses can

help in large scale cultivation of these crops and extraction of starch from them. It is also possible to

modify the starch properties by simple physical methods like hydrothermal or steam pressure

treatments Latest developments in biotechnology can also be tried to modify the starches. These

include fermentation of starch by use of selective organisms or enzymatic modifications which can

bring about specific substitutions. Lot of work has been done on fermentation of cassava and its

effect on starch quality ] whereas the use of enzymes in starch derivatisation has not been exploited

and offers very good scope for value addition

5. Modification of starches. Blending cassava starch with maize and potato

starches modified the viscosity properties with the resulting blend having properties in

between those of the starches [46].

The studies on the bsiac properties of different tuber starches show a wide varuiability in their

physicochemical and functional properties. However they have some undesirable properties.

Therefore attempts have been made to modify the undesirable properties while maintaining the

desrable ones. These include physical and chemical modifications. The physical methods tried is

steam pressure treatment and blending with other starches. . Chemical modifications include

complexation with surfactants and derivatisations like esterifications, crosslinking and oxidation

.

Starch derivatives Since some properties of tuber starches like cohesive texture and

poor viscosity stability of cassava starch, poor clarity and sol stability of colocasia starch are

undesirable in food products attempts were made to improve the properties by chemical

modifications In addition, production of some products by degradation of starch was

attempted. Starch is chemically a polymer of glucose units joined together by (1,4) linkages

and partly. (1,6) linkages. These linkages render the starch susceptible to breakdown by

various chemicals and enzymes unlike cellulose which is much more stable to many chemicals

and enzymes. Thus it is possible to derive various partially degraded products with special

properties suited to various applications in food and industry. In addition the presence of a large

number of hydroxyl groups makes it possible for reaction with various chemical reagents and

physical treatments which can modify the starch properties. These treatments can be degradative

or nondegradative and a number of physical and chemical treatments were attempted. These

include steam pressure treatment, complexation with lipids and surfactants, and chemical

modifications viz. oxidation, derivatisation, crosslinking , etherification and fermentation. The

effect of these treatments on the starch properties described below.

Various surfactants and emulsifiers are added to starch to improve their functional

characteristics and hence a study was conducted to examine how the surfactants affect cassava

starch properties. The results revealed that different surfactants affected the viscosity

differently. Whereas sodium lauryl sulphate increased the peak viscosity, especially at higher

concentrations, the effect of potassium stearate and potassium palmitate was not so pronounced.

Glyceryl monostearate was found to reduce the peak viscosity at higher concentrations . Similar

effect was observed on the 2% viscosity also but to a much lower extent. In addition to peak

viscosity, viscosity stability is important criterion for applicability of starch in food and

industry. In this respect, cassava starch is inferior to maize starch, because its viscosity is

rapidly reduced on heating under heat and shear which leads to a ‘long’ and cohesive texture for

its paste, which is not desirable in food and textile applications. Much effort has been paid to

strengthen the starch paste viscosity. Steam pressure treatment can improve the paste stability,

but it is accompanied by a corresponding reduction in peak viscosity. However, surfactants had

a more desirable effect. On incorporation of potassium stearate or potassium palmitate, even at

0.02% mole concentration/100 g starch, the viscosity was maintained and also stabilised. Since

the surfactants are easily handled and work up is easier the method may be used to modify

starch viscosity.

It was found that sodium sulphite has a special effect on the swelling of cassava starch.

In an examination of effect of the salt at various concentrations, at the concentration of 0.05%

and 0.1% sulphite there was a dramatic fall in the swelling volume. Above this concentration,

the swelling volume recovered to original value. The anomalous behaviour has been attributed

to superoxide induced oxidative reductive depolymerisation of starch . At higher levels of the

salt and in presence of oxygen scavenger propyl galate the effect was absent. Similarly the

effect was absent in the Brabender Viscograph showing that the reaction is very specific to

levels of oxygen. This type of thinning can have some applications which require starch

solutions which have low viscosity levels.

Ester derivatives were prepared from starch by different procedures . Various acids and

anhydrides were used for esterification. The reaction was attempted using the following

systems.

1. Direct reaction with the acid

2. Reaction of acid/anhydride in presence of alkalies

3. Reaction of acid with starch in presence of catalysts

4. Reaction with acylating agents;

Direct reaction with acidThe esters prepared by direct action of acid were (a) formic (b) isobutyric (c) glycolic

(d) thioglycollic derivatives.

The degree of substitution (D.S) obtained by using different acids are given in Table 4.

Lactic acid did not give an ester on direct reaction with starch due to its weakly acidic nature.

Reaction of acid/anhydride in presence of basesThe acid or its anhydride was reacted with the starch in presence of different bases. The

bases tried included dilute alkali, pyridine, triethanolamine and triethylamine. In case of dilute

alkali, though the yield of the products was good, the degree of substitution was low. Further

substitution could be achieved by treating the samples again with acid anhydride and dilute

alkali. However such repeated treatments could not increase the degree of substitution above

0.3.

It was observed that a high degree of substitution was obtained when pyridine was used

and the maximum possible D.S= 3.0 was achieved when pyridine in combination with

anhydride was used. By controlling the amount of acid/anhydride used, desired level of D.S

could be obtained.

The other bases tried for the reaction, viz. triethanolamine and triethylamine did not give

good D.S. indicating that their basicity is not enough to form stable complexes with the acid.

Table 4: Yield , nature and properties of different ester derivatives of cassava starchYield g25-1gStarch

D.S Viscosity(Seconds)

Mode ofpreparation

1. Formyl 20.7 0.23 50.0 Direct reactionwith acid

2. Glycollic 18.8 0.20 44.0 Do3. Thioglucollic 18.0 0.19 44.0 Do4. Isobutyric 19.3 0.22 51.0 Do5. Citric 24.2 0.05 58.5 Do6. Malic 22.5 0.06 56.5 Do7. Tartaric 22.9 0.02 60.0 Reaction with

acid/anhydridein dilute alkali

8. Succinic 23.5 0.10 57.0 Do9. Stearic 22.0 Very low - Do10. Phthallic 23.2 Very low - Do

Catalytic esterification

The esterification of cassava starch was tried with various catalysts. Metal halides were

used in the reaction of the starch with acetic anhydride in acetic acid. The catalysts tried were

ZnCl2, SnCl2, MnCl2 and AlCl3. The results showed that SnCl2 gave highest D.S. followed by

ZnCl2 .

The catalytic effect of perchloric acid on acylation of cassava starch was tried The

results showed that the optimum temperature for the reaction to give good yield and a

reasonable level of substitution was 30°C. Propionic anhydride in presence of perchloric acid

gave similar results. The D.S of the esters could be determined by finding out the intensity of

the 1680 cm-1 absorption in the IR spectrum.

The gelatinisation temperatures were slightly lowered by increasing

the substitution. The associative forces are weakened by substitution of

the hydroxyl groups and hence the earlier gelatinisation. Viscosity at

75°C also showed a fall with increasing substitution, again due to the

reduction of associative forces. Clarity was improved to a small extent

by substitution by acetyl or propionyl groups. The paste stability is as

high as 10 days when the D.S is around 0.10. This property is desirable

for food purposes, where the tendency of starch to retrograde, especially

on freezing and thawing , poses a problem.Ferrous sulphate and hydrogen peroxide catalysis did not give any notable level of

substitution.

Reaction with acylating agents

Attempts to prepare esters by using sodium acetate-acetic anhydride gave a D.S of 0.05.

The viscosity of the starch was 46.0 seconds (Redwood No.1) , gelatinization temperature was

48-65°C and it had acceptable clarity and good sol stability.

The different ester derivatives prepared, their method and D.S are summarised in Table

4. It was generally observed that higher levels of substitution were obtained when pyridine was

used as the base and the anhydride of the acid was used for the reaction. However, as noted for

acetyl derivatives, the sol stability was reduced when pyridine was used for the reaction.

Among the various derivatives prepared, acetyl derivative was found to be the easiest

to prepare and had desirable properties. It was found that phthallic and stearic esters could be

obtained only in low levels of substitution, probably due to steric factors.

Chloroacetic ester of starch was prepared by reaction of chloroacetic acid with starch

suspended in KOH solution at low temperatures. However D.S was low and the product did not

possess good thickening property.

Cross linking

Starch granule strength could be improved by cross linking with poly functional

reagents. These reagents bridge the starch molecules and prevent the breakdown under heat and

hence reduce the cohesive nature of starch and minimise viscosity fall during holding period.

The crosslinking agents used were epichlorhydrin, phosphoric acid and phosphorus

oxychloride. The crosslinked products were obtained by standard procedure and showed

improved stability. A sample of phosphate crosslinked starch had higher viscosity and less

cohesive texture. Though higher crosslinking levels are achieved by using epichlorihydrin or

phosphorus oxychloride, these reagents are difficult to handle and the reaction conditions are

very selective (pH and temperature should be kept within specific ranges). The phosphate ester

on the other hand can be prepared easily using phosphates and has no toxic effects. Hence this

reagent is preferred to bring about crosslinking.

Oxidative reactions

Oxidation of starch can lead to various products depending on the oxidising agent used.

Oxidised starch gives a clear fluid and adhesive paste which does not form a hard gel on cooling

but retains its free flowing, adhesive nature. Films formed from oxidised starch pastes are

strong, tough and horny, in contrast to the weak and brittle films of acid modified starches or

dextrins. Oxidised starch has maximum use in paper industry and also in drilling muds as

dispersant. Dialdehyde starch which is obtained by cleavage of 2,3-diol bond is useful for we-

end application in paper industry. The basic polymeric structure is maintained and hence

dialdehyde starch can be useful for synthesis of polyols.

Oxidation of starch was tried with bromine under steam pressure. The amount of

bromine used, the pressure and time of treatment were varied. The final product obtained was

analysed for reducing value and viscosity. It was found that starch is degraded to a large extent

during the oxidation by bromine as indicated by increased reducing values and decreased

viscosity. There was no effect of sodium peroxide or benzoyl peroxide on the products under

different conditions showing that the reaction is not radical initiated.

Dialdehyde starch was prepared by oxidation of cassava starch with potassium

metaperiodate The dialdehyde starch did not give blue colour with iodine, indicating that it

loses the helical structure required for iodide-starch complex. The loss in the coiled nature is

probably due to absence of enough hydrogen bonds to stabilise the coiled structure and also due

to formation of hemiacetal type of structure by internal bond formation. This is confirmed by

the fact that the dialdehyde starch shows only a very weak peak at 1680-1700 cm-1 in its IR

spectrum. However, the dialdehyde starch gave condensation derivatives with hydrazine, urea

and hydroxylamine, though to a small extent. These condensation products were formed in

gelatinous form and were difficult to crystallise.

Oxidised starch for possible use in drilling muds was made by permanganate and

chromic acid oxidation. The starch was oxidised by using aqueous 0.05M permanganate and

0.5 M HNO3 or 0.1 M sodium dichromate and concentrated HNO3. The products stained blue

with iodine and exhibited weak carbonyl absorption in the IR spectrum indicating that no 2-3

diol bond cleavage had taken place.

Pregelatinised Starch

Pre-gelatinised starch is used in various instant foods, since it is more miscible in water

or milk compared to raw starch. Pre-gelatinised starch was prepared by heating, with

continuous steady stirring the starch with minimum amount of water required to gelatinise the

starch, until the starch was completely gelatinised (as evidenced by the translucency of the

paste). After heating was stopped, the slurry was spread out into a thin film and dried in the sun

or in an oven at 60-65°C. The dried sample was powdered while hot and stored by keeping out

of contact with moisture. The finely ground material was used for various preparations. A

formulation including the pregelatinised starch, cocoa powder and sugar was found to be quite

acceptable in taste and quality and was miscible in hot and cold milk and serve as an infant

food.

Modification by fermentation

Six varieties of cassava having varying HCN contents were subjected to fermentation by

a mixed culture inoculum comprising of Lactobacilli, Corynebacteria and yeast cells. The

properties of the starch extracted from the fermented tubers were studied for possible

modification during fermentation. Apparent reduction in total and soluble amylose contents was

observed. Differential Scanning Calorimetry of the samples indicated that the enthalpy of

gelatinisation was reduced, but the gelatinization temperature was enhanced. Marked reduction

in Brabender viscosity values of starch from fermented tubers was observed, but he X-ray

diffraction patterns remained unaffected. All these changes could be attributed to the presence

of fibrous material and consequent reduction of starch content in unit volume rather than any

major change in the granular structure of starch.

Value added products from starch

Starch adhesives

The simple starch adhesive was made by dissolving starch in dilute alkalie withcontinuous stirring and chemicals like urea and borax were added to improve tack. Finally asmall quantity of formalin was added as preservative. Use of Carboxymethyl cellulose and /orsodium silicate enhanced the viscosity. Use of glycerol did not improve the properties. A dryadhesive was made by the following technique. Starch containing 35% moisture was mixedthoroughly with 0.1 part of phosphoric acid and 1 part of urea. The moist mixture was driedunder vacuum to 7% moisture level and mixed with 0.5% tri-calcium phosphate. The slurrywas heated to 125°C with vigorous stirring and maintained at this temperature for 1 hr. Theyellow product when mixed with 4 parts water and boiled, gave a transparent paste, which didnot settle or become thick. Anti-fungal and antibacterial agents and stabilisers were added.This paste can be conveniently used as remoistening gum. Starch paste was also made bydissolving the starch in calcium chloride solution. The stability could be improved by addingsome glycerol.

Adhesives were prepared using cassava starch with polyvinyl alcohol (PVA). PVA was

dissolved in cold or hot water, pregelatinised starch was added to give a ratio of starch:PVA 1:1

and stirred thoroughly for 2 hours until a uniform paste was obtained. To this material a

plasticiser was added to maintain the uniformity of the paste. An antimicrobial agent (either

copper sulphate crystals or 40% formalin) was introduced to ensure good storage life for the

sample. The samples were tested for their efficiency in the following systems : paper and paper;

paper and cardboard; plywood and hardwood; wood and wood ; ceramic and wood and

ceramic and ceramic. The procedure adadpted for testing the samples was based on the one used

at Forest Research Institute, Dehradun The paste was applied to the surfaces of the two

materials and they were placed together and a weight of 2 or 3 Kg was kept on the sample for 3-

6 hours. Afterwards the weight was removed and the pieces were tried to be separated by pulling

using hand. A good adhesive is indicated by the surfaces sticking together not peeling away.

The paste had excellent adhesive property in all the systems except in plywood and

wood;ceramic. It was found to be most superior for ceramic:ceramic system and thus holds

promise in the building sector. The drawback in the paper; wood and plywood; paper system

was the hygroscopicity affected the stability and slowly there was decrease in the adhesiveness.

For the ceramic:ceramic system, there was no letup in the stickiness even after prolonged storage

even in humid conditions. This should serve as a good substitute for the synthetic pastes similar

to fevicol. etc. In order to improve the resistance to moisture, hot water soluble PVA was used

instead of coldwater soluble PVA and poly vinyl acetate was used in place of polyvinyl alcohol.

Dioctyl phthalate was found to give good appearance and also good stability to the paste. It was

also found that use of urea or borax in small quantities was helpful in increasing the pastiness of

the samples.

Carboxymethyl starch

The conditions for the production of carboxymethyl starch were tsandardised at the laboratory

level. The basic process consists of treating starch with alcoholic alkali to obtain a granular

suspension to which the monochloroacetic acid or sodium salt of the acid is added and stirred for

4 hours. The product is precipitated in excess ethanol or methanol , filtered and dried to obtaina

slight cream coloured product having high solubility and viscosity. The viscosity obtained was

three times higher than that of starch at the same concentration. This product has high demand

in textile and adhesive industries. The process was further modified to reduce the quantity of

alcohol required for precipitation of the derivative. Three entrepreneurs are interested in the

technology and it is expected that the know how will be transferred in the near future.

Cold water miscible starch was prepared by solubilising the starch in dilute alkali and

precipitaion in alcohol. The resulting granular product is transparent, miscible in water and

possesse good viscosity. The product has potential as instant starch in textile applications.

Starch phosphate was prepared by reaction of starch with phosphates in presence of urea and

borax. The required quantity of the chemicals was dissolved in minimum quantity of water and

the starch was thoroughly mixed. After drying overnight, the powder was subjected to heat

treatment for 4 hours at 145°C and then washed with water-alcohol mixture to remove

dextrins. A final washing with excess methanol yields a product with high viscosity, stability

and solbility.

Fructose syrup.

The

Tab. 1. Yield and total amylose content for starches extracted with ammonia solutionand waterSpecies Extraction medium Yield(%) Total amylose

( blue value)Cassava Water 21.8 0.54 0.37 0.012Cassava NH3 22.2 0.37 0.37 0.019Cololcasia Water 6.2 1.79 0.28 0011Cololcasia NH3 16.2 0.37 0.26 0.017Dioscorea alata Water 17.0 1.43 0.45 0.008Dioscorea alata NH3 18.3 1.0 0.44 0.010Dioscorea esculenta Water 17.7 1.06 0.29 0.004Dioscorea esculenta NH3 18.7 1.14 0.28 0.008Dioscorea rotundata Water 18.8 0.85 0.40 0.010Dioscorea rotundata NH3 19.5 1.16 0.40 0.013Sweet potato Water 13.0 1.02 0.34 0.008Sweet potato NH3 10.9 1.10 0.35 0.013Xanthosoma Water 20.0 0.32 0.38 0.014Xanthosoma NH3 20.5 1.76 0.36 0.015

Table 2. Granule size and shape of different starches

Starch Granule shape Granule Size(m)

Cassava

Round, Truncated, Cylindrical , Oval,Spherical , Compound

5 -40

Sweet potato Round, Polygonal, Oval 5-35

Colocasiaesculenta.

Round, 1-10

Xanthosomasaggittifolium

Round, variable 10-50

Pacchyrhizuserosus

Round, Cupoliform or convex-biconcave

6-35

Arrowroot

Round, polygonal 5-50

Amorphophalluspaeoniifolius

Round, Polygonal, 3-30

Canna edulis

Oval, polyhedral 15-120

D. alata

Oval 16-100

D. esculenta Round, Oval, 2-15

D. rotundata

Oval, Polyhedral 10-70

Coleus Round, oval 5-20

Curcuma sp. 14-46

Tab. 3. Table Varietal differences in starch

Varieties Granulesize (m)

Alkalinumber(ml of0.1 Nalkali)

Reducingvalues

(FerricyanideNo.)

Formicacid

released onperiodate

oxidation (ml of 0.01N Ba(OH)2

Amylosecontent(Blue

value at660 nm0

Pastingtemp. (°

C)

Viscosityof 2%paste

(seconds)

M-4 5.4-35.1 7.2 1.8 6.5 0.530 60.70 58.0Kalikalan 5.4-40.5 9.2 1.8 6.6 0.550 63.70 58.0H-1687 5.4-40.5 8.8 1.4 6.3 0.540 55.68 58.0H-2304 5.4-43.2 8.0 1.4 6.7 0.525 52.68 55.0H-226 5.4-43.2 3.4 1.8 6.65 0.500 55.66 56.0H-97 5.4-43.2 6.2 1.2 7.1 0.535 58.70 55.0H-165 8.1-48.6 7.2 1.6 6.9 0.505 52.65 54.0

Tab. 4. Starch granule size, total and soluble amylose contents in Colocasia starchGranule size* (m) Total amylose

content (%)Soluble amylose

content (%)C-9 5.19 31.1 15.6C-62 2.96 26.3 15.9C-46 4.27 22.1 10.4C-149 3.06 23.4 15.6C-189 3.30 20.8 7.8C-216 3.51 22.1 10.4C-218 3.39 24.7 14.3C-220 3.55 29.2 17.1C- 226 3.16 24.7 16.5C-304 3.20 26.3 13.0* CD- 0.3011

Tab. 5. Yield of starch, granule size and amylose content of Amorphallus starchYield (%) Average granule size

(m)Total amylose

(%)Am 2 7.0 13.03 23.2Am 5 10.0 12.49 23.5Am 14 8.1 10.32 22.9Am 15 12.3 11.12 23.3Am 27 11.1 9.62 23.3Am 32 9.9 10.62 23.2Am 34 12.2 11.69 22.9Am 36 10.5 10.35 23.9Am 43 10.5 10.19 21.9Am 51 14.3 9.85 23.2

Table 6. XRD patterns and Chemical shifts for C1 peaks of

different tuber starches

Starch source Nature of C1 NMR peak XRD pattern

Cassava Doublet A

Colocasia Doublet A

Amorphophallus Doublet A

Pacchyrhizus Doublet A

Xanthosoma Doublet A

Arrowroot Doublet A

D. alata Singlet B

D. esculenta Singlet B

D. rotundata Singlet B

Canna edulis Singlet B

Tab. 7. XRD patterns and absolute crystallinities of starch/flour of different varieties of cassavaVarieties XRD pattern Absolute crystalinity (%)H-97 A 8.8H-165 A 11.27H-856 A 10.16H-1687 A 11.47M 4 A 8.91

Table 8. Amylose content (%) in tuber starches

Cassava 18-28

Sweet potato 16-27

Colocasia esculenta. 10-19

Xanthosoma 15-28

D. alata 16-25

D. esculenta 15-27

D. rotundata 18-27

Pacchyrhizus 17-27

Arrowroot 16-27

Amorphophallus 15-25

Canna edulis 18-29

Table 9. Effect of cetyl trimethyl ammonium bromide on the amylose of different tuber starchesStarch Total amylose

Blue valuesSoluble amylose

Blue valuesCassava 0.32 0.18Cassva+CTAB 0.27 0.13Colocasaia 0.28 0.18Colocasia+CTAB 0.20 0.07D. esculenta 0.29 0.14D. esculenta+CTAB 0.22 0.04D. alata 0.43 0.18D. alata+CTAB 0.38 0.11D. rotndta 0.38 0.18D. riotunddata+CTAB 0.35 0,12Sweet potato 0.38 0.13Sweet potato+CTAB 0.34 0.09Xanthosoma 0.38 0.21Xathosoma+CTAB 0.33 0.15

Tab. 10. DSC data on starch from varieties of cassava

Variety T onset T max T end H cal g-1

°CH-97 69.36 72.29 77.13 3.43H-165 65.35 69.22 74.86 3.27H-856 65.62 70.14 74.94 2.65H-1687 67.12 71.45 75.39 3.15M-4 68.20 73.24 78.54 2.95

Table 11 . DSC parameters of different tuber starchesT onset T max T end H J g-1

Cassava 68.5064.0

71.2ND

74.7276.9

12.416.6

Sweet Potato 61.3

73.2

84.5 15.3

Colocasia 83.23

79.985.68ND

90.0285.0

12.8810.6

D. alata 77.2173.74

81.52ND

85.4480.2

11.615.4

D. esculenta 75.9265.7

79.75ND

85.6875.35

13.6413.25

D. rotundata 79.0272.17

83.12ND

87.9580.8

10.2815.01

Xanthosomasaggittifolium

83.1174.8

85.72ND

90.4179.5

9.0815.22

Pachyrrhizuserosus

63.6 ND 76.6 13.65

Canna edulis 65.35

ND

70.85

16.04

Amorphophalluspaeoniifolius

77.8 ND 83.53 16.6

Arrowroot 68.5 68.5 85.0 15.6

Table 12. Rheological properties of tuber starches in a Bohlin RheometerP (3%) P (4%) P (5%) V (3%) V (4%) V (5%) G (3%) G (4%) G (5%)

Cassava 38-56 17-29 10-25 0.03-0.14 0.3-0.45 0.5-0.8 0.8-1 3.5-6.5 8-22Colocasia

19-90 35-46 22-33 .003-.01 0.05-0.19 0.24-0.47 0.01-0.16 1.3-1.6 2.9-5.8

C. edulis 11-21 8-14 9-15 0.7-1.1 1.2-2.9 2.2-3.2 8-25 35-49 70-93D. alata 12-24 10-20 6-16 0.16-0.33 1.1-2.2 1.6-2.6 6-12 36-53 54-92D. esc 14-70 21-35 14-27 0.01-0.07 0.02-0.08 0.04-0.21 0.02-0.1 0.1-0.28 0.6-5D. rot 9-24 7-15 9-16 0.03-1.8 1.1-2.6 1.2-2.6 12-35 23-39 48-66Amorph 25-29 17-24 17-22 0.12-0.28 0.4-0.8 0.7-0.14 1.4-3.5 7-11 14-23Arrowroot

16-20 14-19 14-18 0.25-0.3 0.45-0.68 0.6-1.05 5-8 8-16 13-23

Pacchyr. 30-73 21-42 13-28 0.01-0.02 0.07-0.11 0.14-0.2 0.04-0.53 0.7-1.7 1.3-3.9Xantho. 27-65 12-20 5-24 0.02-0.1 0.2-0.34 0.1-0.57 0.1-0.9 5-7 1-33

Units of V and G Pascals

Tab. 13. Swelling volume, swelling power and solubility of cassava starch of different varietiesVarieties Swelling volume

ml/g starchSwelling power Solubility

%M4 30.5 38.5 22.8Kalikalan 38.8 51.4 24.8H-1687 25.5 35.1 23.6H-2304 30.5 39.5 24.8H-226 33.8 42.6 27.6H-97 30.5 34.6 17.2H-165 37.8 51.8 27.2Ichyapuram local 41.8 54.3 24.4

Tab14. Solubility, gelatinisation temperature and viscosity

of starch solutions

Solubilityg/100 ml

Gelatinisationtemperature °C

Viscosity (2%)Redwood sec.

Viscosity (2%)after cooling sec.

Glycerol 10 130-145 175 1800Ethanediol 2 110-125 17.5 38DMSO 25 75-85 85 130Formailin 25 70-85 78 139DMF Nil -- -- --Methylcellosolve Nil -- -- --Anisole Nil -- -- --

vii) What is the potential value of the results in increasing the production, productivity, profitability and substantiality of agricultural enterprises in the relevant field ?

viii) That has been the actual impact of these findings onproduction, productivity, and sustainability of agriculturalenterprises in the relevant field ?

ix) Any other impact of the results obtained

x) A concise statement (about 200 words) highlights themost significant of the research work done that youwould like to see in your citation, if chosen

12. List of all publications in bibliographic format arising out ofthe research work related

Enclosed as Annexure -I

13. Whether any patents have been taken out or applied for basedon results of this research work ? If so give details

One patent was filed in the council and is under process ,but the technology has vbeen transferred to an industrial unit inAndhra Pradesh.

14. Whether the research work has been submitted for any other award/recognition?

Part of the findings were included in the Hari Om Trust awarad

and team research awards of ICAR. Results were POSITIVE.

15, Certificate by the applicant

Certified that the statements made in this application regarding the

research achievements are true and to the best of my knowledge.

.

Signature

16. Certificate by the Head of the Institution where research was done

Certified that the Statements made in this application are true to the best of my

knowledge.

Signature and seal17. Forwarding note by the Head of the Institution

I am forwarding the application for Rafi Kidwai Award.

Signature and seal

18. Annexures :

Annexure -I List of Publications relevant to research undertaken

Annexure- II Detailed Bio-data of the applicant

Annexure - III Paper cuttings and patent certificates

1. Moorthy S.N. 1982. Acetylation of cassava starch, Proc. Seminar on Post-harvest technology of cassava, AFST(I), Trivandrum, p. 49-51.

2. Potty,V.P., Maini, S.B., Moorthy, S.N. and Balagopalan C . 1982. Production ofitaconic acid from cassava starch, Proc. Seminar on Post-harvest technology ofcassava, AFST (I) Trivandrum, p. 51-53.

3. Moorthy S.N. 1982. Effect of steam pressure treatment on nature andproperties of cassava , AFST (I), Trivandrum, p. 68-71.

4. Moorthy S.N. , Maini, S.B. 1982. Varietal differences on the properties ofcassava starch, Proc. Seminar on Post Harvest technology of cassava, AFST (I),Trivandrum, p. 71-74

5. Moorthy S.N. 1982. Production of high fructose syrup from cassava starch,Proc. Ahara –82, AFST, Bangalore.

6. Moorthy S.N. 1983. Effect of various treatments on cassava flour quality, J.Food Sci. Tech., 20 , 302-305.

7. Moorthy S.N. 1982. Behaviour of cassava starch in various solventsStarch/Staerke. 37, 307-308.

8. Moorthy S.N. 1985. Acetylation of cassava starch using perchloric acidcatalysis, Starch/Staerke, 37, 307-308.

9. Moorthy S.N. 1986. Properties of Coleus starch Starch/Staerke, 38, 77-78.10. Moorthy S.N., and Ramanujam, T. 1986. Variation in properties of starch in

cassava varieties in relation to age of the crop, Starch/Staerke, 38, 58-61.11. Moorthy S.N. 1985. Effect of different types of surfactants on cassava starch

properties. J. Agric. Food Chem. 35, 1227-1232.

12. Moorthy S.N. 1987. Viscosity and swelling properties of cassava-maizeblends, Proc. National Syrup on tropical tuber crops, Trivandrum , 215-218.

13. Padmaja,G., Balagopalan,C., Kurup, G.T. Moorthy, S.N. and Nanda, S.K.1990.Cassava processing, marketing and utilization in India, III Asian CassavaResearch Workshop, Indonesia, Oct. 21-26.

14. Vijayagopal, K., Balagopalan, C and Moorthy,S.N. 1987. Gelatinisation andliquefaction of cassava flour, effect of temperature, substrate and enzymeconcentration, Starch/Staerke, 40, 300-302.

15. Moorthy S.N. and Nair S.G. 1989. Studies on Dioscorea rotundata starchproperties, Starch/Staerke, 41, 81-83

16. 17. Moorthy S.N. 1991. Extraction of starches from tuber crops using ammonia.

Carbohydrate Polymers., 16,391-398.18. Santha N., Sudha,K.G., Vijayakumari, K.P., Nayar, V.U. and Moorthy S.N.

1990. Raman and infra red spectra of starch samples of sweet potato andcassava . Proc. Ind. Acad. Sci. (Chem. Sci.) 102, 705-712.

19. Moorthy S.N. and Padmaja, G. 1991. Comparative study on digestibility ofraw and cooked starch of different tuber crops., J. Root Crops, 17 (Sp) 255-258.

20. Mathew George , Padmaja G. and Moorthy,S.N. 1991. Enhancement in starchextractability from cassava tubers through fermentation with a mixed cultureinoculum, J. Root Crops, 17, 1-9.

21. Moorthy, S.N., Blanshard, I.M.V. and Rickard, J.E. 1992. Starch properties inrelation to cooking quality of cassava Proc. Meeting of cassava BiotechnologyNetwork, Cartagena, Colombia, 265-269.

22. Moorthy, S.N. , Thankamma Pillai, P.K. and Unnikrishnan, M. 1993.Variability in starch extracted from taro, Carbohydrate polymers, 20, 169-173.

23. Moorthy, S.N. , Mathew George and Padmaja, G. 1993. Functional propertiesof starch flour extracted from cassava on fermentation with a mixed cultureinoculum , J. Sci. Food Agric. 61, 443-447.

24. Mat Hashim, Moorthy, S.N., Mitchell, J.R. , Hill , S.E , Linfoot ,K.J. andBlandshard, J.M.V. 1992. Effect of low levels of antioxidants on the swellingand solubility of cassava starch, Starch/Staerke, 44, 471-475.

25. Padmaja, G ., Mathew George and Moorthy, S.N. 1993. Detoxification ofcassava during the fermentation with a mixed culture inoculum, J. Sci. FoodAgric, 63, 473-481.

26. Padmaja, G ., Mathew George ., Moorthy, S.N., Bainbridge,Z., Plumb, V.,Wood, J.F. and Powell, C.J. 1994. Nutritional evaluation of the starchy flourobtained from cassava tubes or fermentation with a mixed culture inoculum.J. Agric. Food Chem., 42 , 766-770.

27. Moorthy, S.N., Unnikrishnan, M. and Lakshmi, K.R. 1994. Physico-chemicalproperties of some accessions of Amorphophallus paeonifolius, Trop. Sci., 34,371-376.

28. Moorthy, S.N., Rickard, J.E and Blandshard, J.M.V. 1994. Influence ofgelatinisation characteristics of cassava starch and flour on the texturalproperties of some food products, Internatl. Meeting on cassava starch andflour , Cali, Colombia, Jan. 1994.

29. Padmaja, G. Balagopalan, C., Moorthy, S.N. and Potty, V.P. , 1994. Qualityevaluation and functional properties of two novel cassava food products –‘yuca rava’ and ‘yuca porridge’ internal. Meeting in cassava starch and flour,Cali, Colombia, Jan 1994.

30. Moorthy, S.N.,1992. Untapped potential of starch of minor tuber crops., Proc.VIII Carbohyd. Conf., Trivandrum, 89-93.

31. Moorthy, S.N., 1994. Physico-chemical properties of starch of lesser knowntuber crops, Proc.Symp. Newer Developments in Carbohydrates and relatednatural products, Trivandrum , 1994.

32. Moorthy, S.N., padmaja, G. and Maini, S.B. 1994. A rapid method fordetermination of starch in cassava tubers (Communicated to J. Root. Crops).

33. Moorthy, S.N.and Thankamma Pillai, P.K. 1994. Properties of starch of someaccessions of taro, Proc. Internatl.Symp. Trop. Tuber Crops. Trivandrum. Nov.1993.

34. Prem Kumar.T., Moorthy, S.N. , Balagopalan, C., Jayaprakas, C.A. andRajamma, P., 1996. Quality changes in market cassava chips infested byinsects, J. Stored Prod. Res., 32, 183-186.

35. Mathew George, Moorthy, S.N. and Padmaja,G. 1995. Biochemical changes incassava tuber during fermentation and its effect on extracted starch andresidue. J. Sci. Food Agric. 69, 367-371.

36. Moorthy, S.N., Wenham, J.E and Blanshard, J.M.V. 1996. Effect of solventextraction on the gelatinization properties of flour and starch of five cassavavarieties, J. Sci.Food Agric., 72, 329-36.

37. Moorthy, S.N. and Mathew George, 1998, Fermentation of cassava and theassociated changes in physicochemical and functional properties, CriticalReviews in Food Science and Nutrition, 38, 73-121

38. John, J.K., Sunitha Rani, Raja, K.C.M. and Moorthy, S.N., 1999,Physicochemical and enzyme susceptibility characteristics of starch extractedfrom chemically pretreated Xanthosoma saggittifolium roots Starch/Staerke,51, 86-89.

39. Sunitha Rani,V., Jancy K. John, Moorthy, S.N. and Raja , K.C.M. 1998. Effect ofpre-treatment of fresh Amorphophallus paeoniifolius tubers on thephysicochemical properties of starch, Starch/Staerke, 50, 72-77.

40. Moorthy, S.N. and Balagopalan, C., 1999, Novel carbohydrates from cassavastarch, In: Tropical Tuber Crops , Ed. Balagopalan, C., Nayar, T.V.R.,Sundaresan, S., Premkumar, T. and Lakshmi, K.R., Oxford IBH, New Delhi,37-43.

41. 42. Sajeev.M.S and Moorthy S.N.1997, Effect of steam pressure treatment on the

rheological properties of components of cassava based field, J. Root Crops, 23,74-80.

43. Moorthy, S.N. 1999, Effect of steam pressure treatment on thephysicochemical properties of Dioscorea starches, J. Agric. Food Chem., 47,1695-1699.

44. Moorthy, S.N. and Balagopalan, C., 1999,. Physicochemical properties ofenzymatically separated starch from sweet potato, Trop. Sci., 39, 23-27

45. Revamma, R. and Moorthy, S.N., 2000, Effect of sodium thiosulphate on theswelling and viscosity properties of cassava starch, Proc. Internationalsymposium on tropical root and tuber crops, 19-22, January, 2000,Trivandrum, India.

46. Premkumar, T., Moorthy, S.N., Jayaprakas, C.A. and Unnikrishnan, M., 2000Quality changes in tubers from cassava plants infested by scale insects,Aonidomytilus albus, Proc. International symposium on tropical root and tubercrops, 19-22, January, 2000, Trivandrum, India.

47. Balagopalan, C., Moorthy, S.N., Ray, R.C., Laila Babu , Shanthi, B., and Sheriff,J.T., 2000 , Integrated technologies for value addition and postharvestmanagement of sweet potato (Ipomea batatas, Lam) in India, Proc. Internationalsymposium on tropical root and tuber crops, 19-22, January, 2000, Trivandrum,India.

48. Moorthy, S.N., Meizes, Y., and Eliasson, A.C., 2000, Effect of lipids ongelatinisation of starch, Proc. International symposium on tropical root and tubercrops, 19-22, January, 2000, Trivandrum, India.

49. Moorthy, S.N., and Eliasson, A.C., 1999, Starch-lipid interactions of tuberstarches, Proc. XIV Carbohydrate Conference, Madras.

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