HEAT TRANSFER STUDIES OF EQUIPMENTS FOR PRODUCTION OF INDIAN TRADITIONAL

FOODS

A Thesis submitted to the

University of Mysore

for the award of degree of

DOCTOR OF PHILOSOPHY

in

Food Engineering

by

K. VENKATESH MURTHY

Department of Food Engineering, Central Food Technological Research Institute,

Mysore 570 020, INDIA

February 2006

K. Venkatesh Murthy Scientist, Department of Food Engineering, Central Food Technological Research Institute, Mysore-570 020, India

DECLARATION

I hereby declare that the thesis entitled Heat Transfer Studies of

Equipments for Production of Indian Traditional Foods which is submitted herewith for the degree of Doctor of Philosophy in Food

Engineering of the University of Mysore, is the result of the research work

carried out by me in the Department of Food Engineering, Central Food

Technological Research Institute, Mysore, India under the guidance of

Dr. KSMS. Raghavarao, during the period 2001 to 2006.

I further declare that the results of this work have not been

previously submitted for any other degree or fellowship.

K. Venkatesh Murthy Date:23.02.2006

Place: Mysore

CERTIFICATE

I hereby certify that this Ph.D thesis entitled Heat Transfer

Studies of Equipments for Production of Indian Traditional Foods

submitted by Mr. K.Venkatesh Murthy for the degree, Doctor of

Philosophy in Food Engineering of the University of Mysore, is the result

of the research work carried out by him in the Department of Food

Engineering, Central Food Technological Research Institute, Mysore,

under my guidance and supervision during the period 2001 to 2006.

(Dr. KSMS.Raghavarao)

Date:23.02.2006

Place: Mysore

ACKNOWLEDGEMENTS

I express my sincere gratitude to Central Food Technological

Research Institute Mysore and Council Scientific Industrial Research,

New Delhi for giving me an opportunity to continue higher studies.

I would like to express my sincere gratitude to my guide

Dr.KSMS.Raghavarao for his perseverance, persuasion, encouragement

and guidance during the course work.

I wish to express my deep sense of gratitude to Dr. V. Prakash,

Director CFTRI, Mysore for his constant encouragement and interest

shown in the field of equipment design for Indian Traditional Foods, which

would be a specialized and challenging area for engineers.

I express my thanks to Mr. A.Ramesh, Mr. H.Krishna Murty (former

HODs) and Dr. KSMS. Raghavarao, present Head of Food Engineering

for their support. I remember and thank Dr. R.Subramanian and Dr.

KSMS. Raghavarao, for their timely help during my professional career.

I gratefully acknowledge the help of staff of pilot plant Mr.

S.G.Jayaprakashan, Mr. I. Mahesh, Mr. B.V.Puttaraju, Mr. M.Shivakumar,

Mr. M.Nagaraju, Mr. K.Girish, Mr. Umesh, and Mr V.Kumar. Thanks are

also to my elder colleagues Mr R.Gururaj (Rtd), Mr. V.N.Subbarao (Rtd),

Mr. AVS.Urs (Rtd), Mr.D.Laksmaiah (Rtd), Mr. M.V.Srinivas Rao (Rtd),

Mr. Madhu (Rtd).

I also thank Ms. R.Chetana, Mr. Ganapathi Patil, and Mr. S.N.

Raghavendra for helping me during the preparation of this thesis.

I wish to thank my parents for providing me good education and

teaching me good values in life. I wish to thank my mother for giving me

blessings and guidance all these years that has lead to this humble work.

My mother was a silent crusader in shaping-up my personality.

My special thanks are also to my wife, Ms. Chetana who has

always been with me and thanks to my sons, Skanda and Sriram who

were all the while enquiring about the progress of the research work.

I thank and remember all my teachers who taught me good values

in life.

I remember my friend Mr. B.S. Prasad who has taught me to

accept success and failure in the same stride.

K.Venkatesh Murthy

Contents

Declaration by candidate Certificate by guide Acknowledgement List of Figures List of Tables Notations Synopsis Chapter 1: Introduction 1.1.0 History of Foods 1.2.0 Traditional Foods 1.3.0 Engineering Design of Machinery 1.4.0 Traditional Food Machinery Chapter 2: Chapathi Machine 2.1.0 Introduction 2.2.0 Materials and Methods 2.2.1 Materials 2.2.2 Methods 2.2.3 Design of Machine 2.3.0 Results and Discussion 2.3.1 Design and Development 2.3.2 Standardization of Chapathi Dough 2.3.3 Heat Transfer Analysis 2.4.0 Conclusions

Chapter 3: Chapter 3: Dosa Machine Dosa Machine 3.1.0 3.1.0 Introduction Introduction 3.2.0 3.2.0 Materials and Methods Materials and Methods 3.2.13.2.1 Materials Materials 3.2.23.2.2 Methods Methods 3.2.33.2.3 Measurement of Thermal Properties Measurement of Thermal Properties 3.2.4 3.2.4 Design of Machine Design of Machine 3.3.0 3.3.0 Results and Discussion Results and Discussion 3.3.13.3.1 Design and Development Design and Development 3.3.2 3.3.2 Standardization of Dosa Batter Standardization of Dosa Batter 3.3.3 3.3.3 Heat Transfer Analysis Heat Transfer Analysis 3.4.0 3.4.0 Conclusions Conclusions

Chapter 4: Boondi Machine 4.1.0 Introduction 4.2.0 Materials and Methods 4.2.1 Materials 4.2.2 Methods 4.2.3 Measurement of Thermal Properties 4.2.4 Design of Machine 4.3.0 Results and Discussion 4.3.1 Design and Development 4.3.2 Standardization of Chickpea Batter 4.3.3 Heat Transfer Analysis 4.4.0 Conclusions

Chapter 5: Conclusion and Suggestion for Future Work

References Annexure 1 Annexure 2

List of Figures

1.1 Versatile Grating Machine 1.2 Hot air Popping Machine 1.3 Bio Plate Forming Machine 1.4 Integrated Hot Air Roasting Machine 1.5 Continuous Lemon Cutting Machine

2.1 Chapathi Machine

2.2 Chapathi Sheeting Unit

2.3 Pneumatic Extruder

2.4 Improved Pneumatic Extruder

2.5 Dusting and Cutting Device

2.6 Chapathi Baking Unit

3.1 Experimental Set-up for Measuring Thermal Diffusivity 3.2 Graph indicating the increase in Wall Temperature and

Center Temperature of the Copper Cylinder (Dosa

Batter)

3.3 Dosa Machine 3.4 Improved Dosa Machine 3.5 Auto Discharge Assembly 3.6 Floating spreader Assembly 3.7 Floating Scraper Assembly 3.8 Improved Batter/Oil Dispenser 3.9 Microstructure of Dosa Prepared on Different Hot Plate

Materials

3.10 Profilogram of Dosa Made Using Dosa Machine

4.1 Boondi Machine 4.2 Experimental Set-up for Measuring Thermal Diffusivity

4.3 Graph indicating the increase in Wall Temperature and Center Temperature of the Copper Cylinder Chickpea

batter

4.4 Circular Deep Fat Fryer 4.5 Discharge Mechanism 4.6 Improved Circular Deep Fat Fryer 4.7 Improved Discharge Mechanism 4.8 3D Graph Showing the Influence of Die Plate Diameter

on Moisture Content in Batter and Colour Change in

Boondi

4.9 3D Graph Showing the Influence of Die Plate Diameter on Moisture Content in Batter and Texture (crispness) of

Boondi

4.10 Contour Plots Showing the Influence of Die Hole Diameter and Total Colour

List of Tables

2.1 Chemical and Rheological Characteristics of Flour Samples 2.2 Effect of Water and Optional Ingredients on the Rheological

Characteristics of Chapathi Dough

2.3 Effect of Slit Width on the Thickness of Chapathi Sheet 2.4 Effect of Water and Optional Ingredients on the Sheeting

Characteristics of Chapathi Dough

2.5 Effect of Water and Optional Ingredients on the Quality of Chapathi

2.6 Comparative Quality Characteristics of Chapathi Made by Manual and Mechanical Sheeting

2.7 Average Thermal Conductivity (kc) as a Function of Hot Plate Temperature of Whole Wheat Flour

2.8 Average Thermal Conductivity (kc) as a Function of Hot Plate Temperature of Atta

2.9 Complete Heat Balance on the Chapathi Baking Oven 2.10 Estimation of Thermal Efficiency of the Chapathi Baking

Oven

3.1 Wall and Center Temperature of the Copper Tube for Dosa

Batter

3.2 Composition of Rice and Black gram 3.3 Estimation of Thermal Properties of Instant Dosa Batter 3.4 Comparison of Thermal properties of Dosa Batter by

Composition and Experimentation

3.5 Estimation of Thermal Efficiency of the Dosa Machine 3.6 Expansion Characteristic of Rice and Urdh Dhal During

Soaking

3.7 Effect of Temperature on Quality of Fermented Dosa Batter 3.8 Effect of Ingredients on Quality of Dosa Using Conventional

Batter

3.9 Average Thermal Conductivity (kd) as a Function of Hot

Plate Temperature

3.10 Average Radiative Heat Transfer Coefficient (pd) as a Function of Refractory Surface Temperature

3.11 Complete Heat Balance on the Dosa Machine 4.1 Coded and Uncoded Process Variables and their Levels for

Boondi

4.2 Wall and Center Temperature of the Copper Tube For Chickpea batter

4.3 Composition of Chickpea 4.4 Estimation of Thermal Properties of Chickpea Batter 4.5 Comparison of Thermal properties of Chickpea Batter by

Experimentation and Composition

4.6 Complete Heat Balance on the Deep Fat Frying of Boondi 4.7 Sphericity of Boondi Globules 4.8 Central Composite Rotatable Design and Response

Functions

4.9 Analysis of Variance (ANOVA) for fit Second Order Polynomial Model and Lack of fit for Total Colour Difference

and Compressive Strength as per CCRD

4.10 Experimental and Predicted Values of Compression at Optimized Frying Conditions

4.11 Estimated Co-efficient for Polynomial Fit representing Relationship between Response and Process Variables

4.12 Average Convective Heat Transfer Co-efficient (ho) as a Function of Hot Oil Temperature of Boondi Globule

Notations

Stefan-Boltzman constant, (W/m2. h. K4) Hc Emissivity of the hood of Chapathi baking oven Hd Emissivity of the hood of Dosa machine pc Emissivity of the Chapathi pd Emissivity of the Dosa tc Chapathi baking time, (h) td Dosa baking time, (h) v Latent heat of water evaporation, (kJ/kg ) A Constant rate of temperature rise of batter, (C/min)

Ac Area of the Chapathi bottom in contact with the hot plate, (m2)

Ad Area of the Dosa in contact with the hot plate bottom, (m2)

Arc Area of the radiating refractory surface of Chapathi baking

oven, (m2)

Ard Area of the radiating refractory surface of Dosa machine, (m2)

Cpb Specific heat of Chickpea batter, (kJ/kg. K)

Cpc Average specific heat of wheat flour, (kJ/kg. K)

Cpd Specific heat of Dosa batter, (kJ/kg. K)

Dc Diameter of Chapathi, (m)

Dd Diameter of Dosa, (m)

Df Degree of freedom

fprc Geometrical factor for Chapathi

Fprc Overall coefficient for radiation heat transfer

fprd Geometrical factor for Dosa

Fprd Overall coefficient for radiation heat transfer

hFc Convective heat transfer coefficient of Chapathi, (W/m2. oK)

hFd Convective heat transfer coefficient of Dosa, (W/m2. oK)

ho Convective Heat transfer co-efficient of groundnut oil, (W/m2 C)

kb Thermal conductivity of Chickpea batter, (W/m.C)

kc Thermal conductivity of the Chapathi, (W/m.C)

kd Thermal conductivity of Dosa, (W/m.C)

Kdb Thermal conductivity of Dosa batter, (W/m. C)

L Moisture loss during baking, (kg)

ma Mass fraction of ash

mc Mass fraction of carbohydrate

mf Mass fraction of fat

mm Mass fraction of moisture

mp Mass fraction of protein

Q1 Calorific value of LPG, (kJ/Kg)

Q2b Sensible heat absorbed by Boondi, (W)

Q2c Sensible heat absorbed by Chapathi, (W)

Q2d Sensible heat absorbed by Dosa, (W)

Q3b Latent heat absorbed by Boondi, (W)

Q3c Latent heat absorbed by Chapathi, (W)

Q3d Latent heat absorbed by Dosa, (W)

QAb Total theoretical heat absorbed by Boondi, (W)

QAc Total theoretical heat absorbed by Chapathi, (W)

QAd Total theoretical heat absorbed by Dosa, (W)

QTb Total heat absorbed by Boondi, (W)

QTc Total heat transferred to Chapathi, (W)

QTd Total heat transferred to the Dosa, (W)

q1d Heat lost by the water bath, (W)

q2d Heat gained by batter,(W)

qcc Heat transferred by conduction to Chapathi, (kJ)

qcd Heat transferred by conduction to Dosa,(kJ)

qFc Heat transferred by convection to Chapathi, (kJ)

qFd Heat transferred by convection to Dosa , (kJ)

qRc Heat transferred by radiation to the Chapathi, (kJ)

qRd Heat transferred by radiation to Dosa, (kJ)

r Radius of Boondi Globule, (m)

R Radius of the copper cylinder, (m)

T1 Out side surface temperature of the copper cylinder, (C )

T2 Temperature of batter inside the copper tube, (C )

T3 Surface temperature of Boondi globule, (C )

T4 Core temperature of Boondi globule, (kg)

T5 Temperature of groundnut oil, (C )

Tc Temperature of Chapathi, (C )

Tcb Chapathi bottom surface temperature, (C )

Tcd Wheat flour/dough temperature, (C )

Tct Temperature of the Chapathi top surface, (C )

Td Measured temperature of the Dosa, (C )

Tdb Temperature of the Dosa bottom surface, (C )

Tdd Temperature of Dosa batter at ambient conditions, (C )

Tdt Temperature of the Dosa top surface, (C )

THc Hood (refractory surface) temperature of Chapathi baking oven, (C )

THd Hood (refractory surface) temperature of Dosa machine, (C )

Tp Hot plate temperature, (C )

Tp1 Predicted temperature of the Dosa, (C )

TRc Temperature of the hot air inside the hood, in (C )

TRd Temperature of the hot air inside the hood, (C )

W1 Mass of Chapathi dough, (kg)

W1d Mass of Dosa, (kg)

Wc Mass of Chapathi dough, (kg)

Wd Mass of Dosa batter, (kg)

xc Thickness of the Chapathi, (m)

xd Thickness of the Dosa, (m)

b Thermal diffusivity of Chickpea batter, (m2/s)

c Thermal diffusivity of Chapathi dough, (m2/s)

d Thermal diffusivity of Dosa batter, (m2/s)

Duration of Experiment, (Min)

b Density of Chickpea batter, (kg/m3)

d Density of Dosa batter, (kg/m3)

DBNU Dark brown non-uniform

BU Brebanders unit

DGNU Dull grey non-uniform for Chapathi baking oven

LBU Light brown uniform

SEM Standard Error Mean

NS Not significant

Synopsis

The traditional foods have been prepared for hundreds of years

and the art of preparation has been perfected over years and varied

across the country. The attempts to change these food habits have not

been successful to the extent envisaged. As the value of time is

increasing day by day, especially with the working women being the sign

of times, the demand for the ready-to-eat traditional foods is also

increasing. Though the basic kitchen technology for the production of

these foods is known, considerable research and development efforts are

required to translate these technologies to the level of large-scale

production. This requires a lot of input from the food engineers and

technologists. The variation in these foods is so vast that it is very difficult

to treat them under a uniform class. The traditional food prepared and

consumed in one region may not be known in another region. Till recently,

the preparation of traditional foods was considered more an art than

science and the mechanization has been thought of very recently.

The successful operation of any machine depends largely on the

kinematics of the machines. The motion of parts is largely of rectilinear

and curvilinear type. Rectilinear type includes unidirectional, reciprocating

motion while curvilinear type includes rotary, oscillatory and simple

harmonic motions. Design is a process of prescribing the sizes, shapes,

material composition and arrangements of parts so that the resulting

machine will perform the prescribed task. The role of science in the

design process is to provide tools, to be used by the designers as they

practice their art. It is the process of evaluating the various interacting

i

alternatives that designers need for a large collection of mathematical and

scientific tools. These tools when applied properly can provide more

accurate and reliable information for use in judging a design, than one can

achieve through the process of iteration. Thus mathematical and scientific

tools can be of tremendous help in deciding alternatives. However,

scientific tools aid imagination and creative abilities of the designers to

make faster decisions. The largest collection of scientific methods at the

designers disposal falls into the category of analysis. These are the

techniques, which allow the designer to critically examine an already

existing or proposed design in order to judge its suitability for the task.

Thus analysis in itself is not a creative science but one of evaluation and

rating things that are already conceived. Most of the effort is spent on

analysis but the real goal is the synthesis, that is, the design of a machine

or system. However, analysis is a vital tool, inevitably be used as one of

the steps in the design process.

With this in view, development of equipment such as continuous

Chapathi machine automatic Dosa machine and continuous circular deep

fat fryer for Boondi along with the integration of mechanization with the

technological standardization of respective dough/batters is considered in

the present study.

The subject matter of this thesis is presented in five chapters.

Chapter 1: This chapter comprises of general Introduction and scope of

the present investigation, literature review pertaining to the design

ii

fundamentals and design considerations for food processing machines.

Further, the gist of 5000 years history of Indian traditional foods, the need

for mechanization with respect to the present day context and the

objectives of the present study have been presented.

Chapter 2: It comprises of the preamble for Chapathi machine. The

optimization of the moisture content for different wheat flours such as

whole-wheat flour, resultant atta, mixing time and resting time of the

dough are presented and the rheological properties of dough, the

optimum thickness of the Chapathi sheet for machining, the effect of

dusting on the quality of the sheeting are discussed. Engineering and

thermal properties such as shear strength of Chapathi sheet and thermal

conductivity, specific heat, thermal diffusivity of the Chapathi dough are

presented. This chapter presents the approach in understanding and

integrating the thermal and engineering aspects of the Chapathi machine.

The conceptual schematic, the engineering details of machine and the

selection of the engineering materials for different parts are presented.

The working principle of the integrated Chapathi-making machine,

namely, pneumatic sheeting, dusting and cutting devices coupled to the

baking oven are discussed. The conceptual designs of different parts

such as baking oven, custom-built burner are discussed. The energy

balance in order to arrive at the theoretical heat required for the baking of

Chapathi, the residence/baking time based on added moisture and the

heat loss in baking oven, design of the gas burner, air fuel ratio required

for complete combustion of the liquid petroleum gas are also discussed.

iii

The rate of heat transfer and total heat requirement for baking of the

Chapathi is presented. The contribution of different modes of heat transfer

and its relevance to the sensory characteristics of baking Chapathi,

thermal efficiency of the baking oven for Chapathi are discussed.

Chapter 3: This chapter comprises of general introduction of Dosa, an

Indian traditional break-fast food and conceptual design of automatic

Dosa machine. Different parameters essential for the preparation of the

Dosa batter such as soaking time, swelling ratio, moisture uptake during

soaking, final moisture content in batter, mixing and fermentation time are

discussed. The results of this chapter are useful in understanding the

integration of technological and engineering requirements of the

automatic Dosa machine. The Dosa batter was studied under two

categories, namely, conventional batter and instant batter mix (powder).

The optimization of different ingredients for the preparation of the Dosa

batter, effect of added moisture on baking time and product quality are

presented. The rheological properties of the conventional batter as well as

instant Dosa batter in terms of the viscosity at different moisture levels

with the effect on the final product quality, scanning electron microscopic

study to examine the pattern of evaporation of moisture during baking has

been presented. The thermal properties such as specific heat, thermal

conductivity and thermal diffusivity of the Dosa batter are presented. This

section presents the approaches that are useful in calculating the

theoretical heat requirement of the automatic Dosa machine and in turn

design of the circular burner. Trained panelists from sensory science

iv

department of CFTRI evaluated the product prepared using the automatic

Dosa-machine. The product prepared from both conventional and instant

batters are evaluated by the panelists for various attributes for the

sensory evaluation of the product and the results are presented in this

section. The results of this chapter are useful in understanding the market

acceptability of the machine made product.

The principle of operation and salient features of the automatic

Dosa-machine are discussed. The heat transfer study across the hot plate

of the machine, the quality parameters of the product produced using hot

plates of different materials such as stainless steel, cast-iron, alloy steel

and teflon coated aluminum and the microstructure along with the sensory

aspects of the product produced using these hot plates have been

discussed. The Dosa machine has a circular burner for supply of heat to

the hot plate, which is designed to be concentric to the circular hot plate.

Based on the theoretical heat estimate, including the operational losses,

the dimensions of the burner, number as well as diameter of the holes

and the size of the mixing tube along with the required air fuel ratio are

presented. The scraper is an important sub-assembly in the automatic

Dosa-machine. It is a straight edged strip of stainless steel, which rests on

the rotating hot plate. The curvilinear motion of the hot plate against a

straight edge will aid in scraping the Dosa from the hot plate and also roll

the product into a presentable form. A circular scraper, which is an

improvement over the straight edged scraper, not only scrapes and rolls

the product but also discharges the product from the hot plate in to the

collection chute is presented in this section. The heat transfer studies and

v

analysis of different modes of heat transfer, their individual contribution

towards the product quality, theoretical heat requirement, thermal

efficiency and sensorial properties of the product are presented. Based on

the heat transfer studies, which clearly indicated mode of heat transfer to

be more important than the quantum of heat transferred and accordingly,

the design modifications are incorporated in the machine. Baking

temperature, baking time, sensorial attributes, textural properties of the

product such as colour, shear strength are discussed in this chapter.

Chapter 4: This chapter comprises of general introduction of Boondi, (as

a snack food) conceptual design of continuous forming device and

continuous circular deep fat fryer. Different ingredients essential for the

Chickpea batter, final moisture content in the batter and the mixing time

are also discussed. The results of this chapter are useful in integrating the

engineering and thermal aspects of the continuous forming device and

continuous circular deep fat fryer. Optimization of different ingredients for

the preparation of Chickpea batter, effect of added moisture on frying

time, diameter of the forming die, height of fall of the globule from the

forming die to the top of the oil bath and product quality are presented.

The rheological properties of the Chickpea batter, with varied added

moisture, in terms of the viscosity and their effect on the final product

quality has been presented. The thermal properties such as specific heat,

thermal conductivity and thermal diffusivity of the Chickpea batter are

presented. Calculation of the theoretical heat requirement of the

continuous circular deep fat fryer and its application in design of the

vi

circular burner are also discussed. The product prepared from the

Chickpea batter was evaluated for various attributes of the sensory

evaluation of the product and their observations are presented in this

section. The results of this chapter are useful in understanding the

integration of the technological and mechanization of the process besides

the market acceptability of the machine made product.

The principle of operation and salient features of the forming and

frying machine are also discussed. The conceptual design for continuous

forming device and continuous circular deep fat fryer having different

parts such as the forming sub-assembly, discharge mechanism for the

fried product; custom built circular burner etc are discussed. The

theoretical heat required for frying of Boondi, the residence/frying time

based on added moisture and the heat loss in the frying machine are

discussed. The continuous circular deep fat fryer has been designed with

a circular burner for supply of heat to the oil, which is concentric to the

circular trough. Based on the theoretical heat analysis including the

operational losses, the dimensions of the burner, the number and

diameter of the holes, size of the mixing tube along with the required air

fuel ratio are arrived at. The discharge mechanism is an important sub-

assembly in the continuous circular deep fat fryer. The discharge

mechanism has to work inside a circular rotating trough picking up the

fried product from the hot oil bath while draining the excess oil. The heat

transfer studies of the continuous circular deep fat fryer is presented in

this section. The theoretical heat analysis, thermal efficiency and

sensorial properties of the product are also presented. The frying

vii

viii

temperature, frying time and textural properties of the product such as

colour, shear strength and sensorial attributes are also discussed in this

chapter.

Chapter 5: This chapter contains the conclusions of the work

carried out during the development of the different machinery for Indian

traditional foods. It also highlights the importance and scope in design and

development of machinery for diverse Indian traditional foods, which can

be a specialized area of research for future work.

Section 1.1.0: History of Foods

Over the last few hundred centuries, the glacial ages have

alternated with warm epochs. Following the last warm period, about

15,000 years ago, man came to his own, starting off as a food gatherer

and then gradually evolving as a food cultivator. During this long phase

fruits appeared to be his main dietary item. The development of

agriculture after about 10,000 BC rapidly changed the dependence on

constant hunting for animal food (Achaya, 1994). In the course of a few

millennia meat declined even further, and the agricultural/horticultural

produce started to dominate the diet. At every place around the world

where human evolved, a similar evolutionary pattern has characterized

the kind of food that he/she consumed. This can be deduced from the

evidence that was left behind by way of tools, cave paintings, and

surviving words.

Every community that lived in India has a distinctive food ethos.

Most of these, however, have been influenced by Aryan beliefs and

practices. Originally starting from the North and North-West of India,

Aryan ideas gradually expanded all over the country, sub-suming earlier

practices and exerting a strong influence on those cultural beliefs that

appeared later.

Food for Aryan belief was not simply a means of bodily

sustenance; it was part of cosmic moral cycle and Bhagavadgita says,

From food do all creatures come into being. In the great Aryan cosmic

1

cycle, the eater and the food he eats and the universe must all be in

harmony and all of these are different manifestations of same essence.

The domestic hearth in a Hindu home was considered an area of

high purity; even of sanctity, in fact, it was set up adjacent to the area of

worship. The domestic hearth had to be located far away from waste-

disposal area of all kinds and demarcated from sitting, sleeping and visitor

receiving areas (Achaya, 1994). Before entering the cooking area, the

cook was to take bath and don unstitched washed clothes. The objective

of cooking is not simply to produce materials suitable for eating but to

conjoin the cultural properties of the food with those of the eater.

Section 1.2.0: Traditional Foods

Indian traditional foods have a long history and the knowledge of

preparing them has been passed on from generation to generation.

Efforts have been made to document this vast knowledge, which is in the

domain of a few families/individuals. Large number of traditional foods are

being consumed by people in different geographical locations in the

country. Indian sweets and snack food industry are on the threshold of

revolution and identified to have good export potential. Central Food

Technological Research Institute (CFTRI), Mysore has made a significant

contribution in this context towards the process development and

mechanization.

2

1. Chapathi

A variety of breads have been developed from wheat, which is the

main staple food in India. The term bread is hardly appropriate for a

numerous roasted, fried and baked items of India. Dry baked forms of Roti

include the common Chapathi, baked dry on a hot plate (thava), some

times puffed out to a Pulka by brief contact with live coal/flame. A very

thin Chapathi prepared in Gujarat state is the Rotlee. The Rumali Roti

(scarf) is also thin but much bigger in size. The Bhatia made in the state

of Rajastan, are soft, thin Roties that come apart as two circles because

of the style of rolling of the dough. Dough carrying spinach yield distinctive

Roties, the Missiroti, baked dry on a thava, flaky in texture, has spinach,

green chillies and onions in the dough. The Kakras are kneaded with milk

and water and are crisp products that keep well for longer periods and are

carried by Gujarathi travelers.

Wheat products after rolling out can be either pan baked using just

a little fat, or baked with out fat. Paratas are the most common, often

square or triangular in shape rather than circular. The dough can be

mixed with seasoned vegetable like potatoes, spinach or methi and these

products are eaten with curds. Poories are deep fried products made from

wheat flour and some times the dough is mixed with sugar or fat. The

dough of the Bhatura is allowed to ferment using yogurt, and then rolled

out to give a layery fried product (Achaya, 1994).

The other category of the wheat based product which are

unleavened and baked, either in closed or heated oven or in Indian style

3

tandoors, which are open, lined, glowing ovens with live coals placed at

the bottom. Naan is made of maida, the white inner flour of wheat, which

is leavened before baking to yield a thick elastic product. Naan is normally

dressed with either saffron water or tomato to give red surface colour after

baking.

2. Dosa

Food was delicious and varied in South India in the first few

centuries AD. Rice was converted into many appetizing foods. The appam

was a pancake baked on a concave circular clay vessel and a favored

food soaked in milk. The other forms of shallow pan-baked snack were

Dosai and adai, both based on rice. The Dosa is now made by fermented

batter, a mixture of ground rice and urdh dhal and the adai is made from a

mixture of almost equal parts of rice and four pulses, ground together

before shallow baking.

The tosai (Dosai) is first noted in the Tamil Sangam literature of

about 6th century AD. It was then perhaps, a pure rice product, shallow-

fried in a pan, while the appam of similar vintage was heated without fat

on a shallow clay chatti (pan). Today the Dosa is made from fermented

batter and Dosa of Tamil Nadu is soft, thick product, while that of

Karnataka is thin, crisp and large. It is frequently stuffed with a spiced

potato mash to yield the popular masala-Dosai.

4

3. Idli

In Tamil literature the ittali is first mentioned only as early as the

Maghapuranam of the 17th century AD. The Manasollasa of about 1130

AD written in Sanskrit describes the Iddarika as made of fine urad flour,

fashioned into small balls, fried in ghee and then spiced with pepper

powder, jeera powder and asafetida. In Karnataka, the Idli in 1234 AD is

described as being `light, like coins of high value, which is not suggestive

of a rice base. The steaming vessel in Kannada is allage, and the iddalig.

In all these references, three elements of the modern Idli are missing.

One is the use of rice grits (in the proportion of two parts to one of urad).

The next is the long process of grinding and the overnight fermentation of

the ground batter. The last is the steaming of the fermented batter. The

literature does not offer certain answers as to when in the last few

centuries these elements entered the picture.

In 1485 AD and 1600 AD, the Idli is compared to the moon, which

might suggest that rice was in use; yet there are references to other

moon-like products made only from urad flour. The Indonesians ferment

many materials (soyabeans, groundnuts and fish) have a similar

fermented and steamed item called kedli. Steaming is a very ancient form

of food preparation in the Chinese ethos, referred to by Xuan Zang saying

that in the 7th century AD India did not have a steaming vessel. It has

been suggested that the cooks who accompanied the Hindu kings of

Indonesia during their visits home (often enough looking for brides) during

the 8th to 12th centuries AD, brought fermentation techniques with them to

5

their homeland. Perhaps the use of rice along with the pulse was

necessary as a source of mixed natural microflora needed for an effective

fermentation. Yeasts have enzymes which break down starch to simpler

sugar forms and bacteria which dominate the Idli fermentation carry

enzymes for souring and leavening through carbon dioxide production.

Even Czechoslovakia has a similar steamed product called the Knedlik

(pronounced needleck). Steaming can of course be achieved by very

simple means, merely by tying a thin cloth over the mouth of a vessel in

which water is boiled and its antiquity would be impossible to establish. It

is not unlikely that the name of the Idli persisted even though its character

changed with time, resulting in diversified forms of Idly (Achaya, 1994).

Section: 1.3.0: Engineering Design of Machinery

Designing process requires an organized synthesis of known

factors and the application of creative thinking. Design and production, the

two principal areas of technical creativity are closely interrelated. The

designer has to keep in mind, the product designed to be manufactured in

the most economical way. Apart from the knowledge in manufacturing

aspects, he/she must be in touch with the consumer needs to design the

machine to suit their requirement. Regulations, national codes, safety

norms are to be given due consideration and these often play a decisive

role in determining the final design.

The machine design can be broadly classified into three categories

as adaptive design, developmental design and new design. In adaptive

design the designer is concerned with the adaptation of the existing

6

design. Such design does not demand special knowledge or skill and the

problems can be solved with ordinary technical training. A beginner can

learn a lot from the adaptive design and can tackle tasks requiring original

thoughts. A high standard of design ability is needed when it is desired to

modify a proven existing design in order to suit a different method of

manufacture or to use a new material. In developmental design, a

designer starts from an existing design but the final result may differ quite

remarkably from the initial product. This design calls for considerable

scientific training and design ability. New design, (which never existed

before) is done by dedicated designers who have sufficient personal

qualities of high order. Research, experimental activity and creativity is

aptly required.

In the actual design work in industries one need not design the

simple elements like bolt or nut every time and most of these elements

are readily available to meet standard specifications. A designer is

required to select these elements properly and put them together to meet

the requirements and this process of selection of elements and their

configuration is usually termed as system design. It is usual to break

down the complete system into a series of sub-assemblies, components

and materials and these sub-assemblies can be further broken down to

single detail parts each of which is made from raw material. In system

design, a designer has to properly think of a device capable of giving

required output for a given input; devise means and obtain the emergent

properties of the elements and system and their configuration; study the

feasibility of elements and system; examine the compatibility and

7

interconnection of elements and system; and find the optimized design or

select the best system. System design means design of complex system

comprising of several elements. It should always be remembered that

requirement for a design concern demand, function, appearance and cost.

It is known that every process is a combination of three elements,

namely, the man, machine and material. A change in any one of these will

result in a change in the process. All these three elements are subjected

to inherent and characteristic variations. These variables result in the

variation in size of components. Due to inevitable inaccuracy of

manufacturing methods, it is not possible to make any part precisely to a

given dimension and it can only be made to lie between maximum and

minimum limits. The difference between these two limits is called the

permissible tolerance. The tolerance on any component should be neither

restrictive nor permissive and should be as wide as the process demands.

Generally in engineering, any component manufactured is required to fit

or match with some other component. The correct and prolonged

functioning of the two components matched (assembled parts) depends

up on the correct size and relationship between the two. Thus by variation

of hole and shaft sizes, innumerable types of fits can be possible. The

limits and fits provide guidance to the user in selecting basic functional

clearances and interferences for a given application or type of fit and in

providing tolerances which provide a reasonable and economical balance

between, fits, consistency and cost.

8

Section 1.4.0: Traditional Food Machinery

The popularization of traditional foods is gaining momentum and is

becoming very popular. The increasing consumer demand for high quality

and safe product at affordable price has resulted in a need for

mechanization, in which the food engineers and technologists have a

major role. The mechanization and automation of traditional foods offers a

challenge as many parameters affect the product quality. The trend

towards the urbanization with a concomitant scarcity of domestic help,

increasing trend in the employment of housewives outside their homes to

supplement the income have increased the demand for ready or

processed foods. The vast variations in the Indian traditional foods made

it difficult to mechanize and also to design a single cost effective machine

to manufacture different types of foods. Some of the food processing

machinery designed at Central Food Technological Research Institute,

Mysore are described below.

1. Chapathi machine

The Chapathi machine comprises of two major sub-units, namely

the Chapathi sheeting unit and the Chapathi-baking unit. Both these units

are integrated into the Chapathi machine in order to produce Chapathi

continuously in largescale automatically. The forming of circular Chapathi

discs of required thickness and diameter is done using the sheeting unit

and the discs are transferred to the Chapathi-baking unit for baking. The

development of the Chapathi machine design includes series

9

of improvements and is presented as improved devices. The invention is

covered by Indian patents.

2. Dosa Machine

Some traditional Indian foods such as Dosa and Idli are becoming

more popular. Dosa, an Indian traditional food is consumed by a large

section of population as a breakfast food. For the largescale production, a

continuous automatic Dosa machine was designed and fabricated. The

machine can handle different types of batter such as conventional batter

as well as instant batter mix (powder). The consistency of the batter, the

timetemperature for baking of the Dosa have been standardized.

Predetermined quantity of the batter is dispensed, spread to uniform

thickness on the hot plate of the machine and baked Dosa are scraped,

rolled and discharged automatically. The invention is covered by Indian

patents.

3. Boondi Machine

The Boondi machine has two sub-units, namely, Boondi forming

unit and Boondi frying unit and both are integrated for continuous

operation. The forming machine has a die, for varying the diameter of the

globules and the unit has the provision for changing the die plates having

different sizes of holes. In order to form Boondi globules, the batter is

made to flow through perforated die under mechanical vibration. As the

batter passes through the holes/perforations of the die, it breaks into

10

globules, fall directly into the hot oil of the continuous circular fryer. The

invention is covered by Indian patents.

4. Versatile Grating Machine

Grating machine is useful for large-scale preparation of gratings of

uniform dimension of fruits, vegetables and coconut (shown in Fig. 1.1).

The gratings obtained using this machine will have application in fruit,

vegetable, coconut and other similar food processing industry. Based on

stationery circular multi pointed cutter, rotating vanes and conical rotor

concept, a device can grate different varieties and sizes of fruits and

vegetables of different geometry and hardness. Raw mango, Carrot,

Amla, Copra (dried), Beet root etc. are a few common types of fruits and

vegetables which are grated using this machine. The invention is covered

by an Indian patent.

5. Hot Air Popping Machine

The hot air popping machine is designed for popping of maize,

paddy, and sorghum. The unit consists of a fluidization chamber, a screw

conveyor for feeding the material into the combustion chamber for

popping and a discharge chute (shown in Fig. 1.2). The popped material

due to the decrease in bulk density (increase in volume) is discharged

through the discharge chute. The startup (heat up) and shutdown times of

the popping are rather instantaneous and the hot air is recirculated. The

direct heat transfer to heating medium (air) and recirculation of hot air

11

increases the thermal efficiency of the popping machine. The invention is

covered by an Indian patent.

6. BioPlate Forming Machine

Traditionally plant residues such as leaves, areca palm sheath

have been used in India for forming into different shapes such as plates,

cups, saucers etc. for serving of foods. Leaves of plants such as of Butea

or Bauhunia are washed, softened and depending on the desired size of

plate, two or more of the leaves are manually stitched together at the

edges, using small sharp pins made of twigs or coconut ribs. Traditionally,

cups and saucers of this nature are also used for vending of butter and

other semi-solid materials. In its construction, the bio-plate forming

machine (shown in Fig. 1.3) consists of a prime mover for the rotary

motion of the die sets, a set of punch and die, an actuating cam, a main

frame and electrical parts. The forming of bio-plate is by the process of

thermosetting of the leaves and axial thrust with heat is applied through

the punch and die set. The invention is covered by an Indian patent.

7. Integrated Hot Air Roasting Machine

Roasting is a high temperature short time heat treatment operation

and is done to enhance the organoleptic properties of food materials. The

roasting, resting and cooling decks are incorporated in a single machine

so that the three operations are done sequentially. The integrated hot air

roasting machine (shown in Fig. 1.4) was employed for roasting/toasting

of cereals, pulses, spices, oil seeds and ready to-eat snack foods using

12

flue gas. The product processed by using this device has uniform color,

moisture and other sensorial properties. The material is processed under

hygienic conditions in a continuous manner. All the variables such as

residence time, temperature of the hot air, resting time and cooling time of

the roasted material are done sequentially using a programmable logical

controller (PLC). The device is energy efficient as the hot air is

recirculated. The invention is covered by an Indian patent.

8. Continuous Lemon Cutting Machine

The machine relates to a continuous circular cutting machine for

lemon and other similar spherical fruits. The lemon-cutting machine

(shown in Fig. 1.5) is capable of cutting the spherical fruits either into two

halves or into four equal parts. Cut lemon and other similar fruits will have

application in pickle and other similar food processing industry. The

machine design is based on the concept of stationery cutter and rotating

locating rollers. The invention is covered by an Indian patent.

Although design and development of these machinery has been

carried out over the years at CFTRI, the traditional food machinery

considered for detailed study in the thesis are,

1. Chapathi machine.

2. Dosa machine.

3. Boondi machine

13

14

The study is broadly classified into two categories, namely, i)

Design of machinery and technology of preparation of traditional foods

and ii) integration of the two.

The technology aspect of the study involves standardization of

relevant food materials to meet the requirement of the machines and

study of their thermal properties for the completeness of the design of

these machines. Several Indian patents extensively cover the above

inventions (Venkateshmurthy et al., 1997, 2000, 2001, 2002, and 2005).

The theoretical studies carried out were of immense use in

improving the design of these machines to achieve near perfection. Many

a time the machines were modified to suit the food material and the food

formulations were modified to adapt to the engineering design. The

process of iteration helped in matching the machine to food and food to

machine and finally resulting in a good match.

Schematic of Machine Development

Thermo physical properties Processing

Thermal properties

Technology of Food

Food processing machinery

Food machinery

Physical properties Conceptual schematic

Standardization of Ingredients Thermal Diffusivity

Thermal conductivity

Specific heat Standardization of preparatory

operations

Energy / Heat requirement

FOOD PROCESSING MACHINE

Fabrication

Engineering Design

1.1: Versatile Grating Machine

16

Fig. 1.2: Hot Air Popping Machine

17

Fig. 1.3: Bio Plate Forming Machine

18

Fig. 1.4: Integrated Hot Air Roasting Machine

19

Fig. 1.5: Continuous Lemon Cutting Machine

20

Section 2.1.0: Introduction

As traditional staple foods in India, Chapathi and Poories stand

next only to cooked rice. In northern parts of the country Chapathi and

Poories are the main staple foods. In large number of industrial and

military canteens hundreds of Chapathis/Poories are prepared and

consumed daily. All the preparatory operations are carried out manually,

which is tedious and time consuming. Attempts to produce and market

pre-cooked and packed fast foods; especially Chapathi are being made

by some agencies with very little success. One of the problems in their

attempts being the non-availability of suitable machinery and gadgets for

preparing them on a large-scale. In case a device is made available for

making Chapathi, from dough mixing to baking/frying, would result in

reduction in labor and drudgery to cater to large number of people in short

time in serving Chapathi of uniform quality. The mechanization would

pave way for the production and marketing of precooked and packed

Chapathi as convenient food in large volumes hygienically.

The design problem can be best approached through a

combination of theory, modern knowledge of materials, awareness of the

limitations and practicability of various production methods. The finest

workshop facility with the most up-to-date machine tools enabling

economic production will be no good if the designer has not done the

work satisfactorily. Machine members have to be so sized, in order to with

stand the resulting stresses and deformation and at the same time

transmit the required motion with constant or variable forces acting on

21

them. The machine elements are to be sized keeping in view the criterion

of wear and the environmental conditions like temperature, corrosion and

other ambient conditions. Since there are many ways of addressing the

same problem and no rigid rules are applicable, as the designers must

rely upon models and other testing techniques to determine whether the

machine will perform satisfactorily.

The successful operation of any machine depends largely on the

kinematics of machines. The motion of parts is largely of rectilinear and

curvilinear type. Rectilinear type includes unidirectional, reciprocating

motion while curvilinear type includes rotary, oscillatory and simple

harmonic motions. Design is a process of prescribing the sizes, shapes,

material composition and arrangements of parts, so that the resulting

machine will perform the prescribed task.

Roti and Chapathi are the staple food in India and different type of

these unleavened breads are prepared from wheat and are baked on a

steel plate (tava) and puffed by bringing it in contact with live flame for a

brief period. Chapathi, normally hand rolled by a pin and plate are baked

on pan using fat. Fermented dough using yogurt and rolling out to give a

layery fried product is called the Bhatura. An Indian styled well-insulated

oven is used for the preparation of unleavened bread called the Tandoori

Roti. Naan is made of maida, the white inner flour of wheat, which is

leavened before baking to yield a thick elastic product.

The numerical values of thermo physical properties of food

products are necessary for design, optimization, operation and control of

food processing plants and quality evaluation of products. Most of the

22

design and operation of food process and processing equipment have

been based more on the industrial experience and empirical rules, than

on engineering science. This is due to the complex physical and chemical

structure of raw and processed foods and the diversity of food processing

operations and equipment. Advanced mathematical modeling, computer

simulation, process control and expert systems of food processing require

quantitative data of transport and other engineering properties.

Previously, heat transfer analysis for heating or cooling of food

products employed constant uniform values of thermal properties. These

analysis being over simplified were always inaccurate. Present day

analytical techniques such as finite element and finite difference methods

are much more sophisticated and can account for non-uniform thermal

properties, which change with time, temperature and location as a food

product is heated/cooled. This greatly increases the demand for more

accurate thermal property data and more sophistication in the sense it is

necessary to know how thermal properties change during a process.

Though there are many reports on the measured values of the

thermal properties as well as on mathematical models for their estimation,

it is often necessary to make measurement for special cases, or at least

to verify the literature values or the validity of the models because of the

great variation in origin, composition and processing of food.

Literature Survey

There are very few reports of development of machinery for Indian

traditional foods. Some of the machines designed and developed earlier

23

are a) Continuous Chapathi machine based on screw extrusion and three

tier baking oven (Gupta, et al., 1990), b) Design and development of an

Idli machine and vada machine (Nagaraju, et al, 1997), c) Dosa machine,

Boondi machine, Bio-Plate casting machine, Grating machine, Laddu

machine (Venkateshmurthy, et al., 1997, 2000, 2002, 2004) and

Continuous Rice cooker (Ramesh, et al., 2000).

The theoretical aspects of the estimation of thermal properties

such as specific heat and thermal conductivity, in order to design

continuous baking oven for Chapathi, Indian unleavened flat bread has

been described (Gupta, 1990). Though a good amount of work has been

reported on thermal conductivity of biological materials, practically no data

is available for wheat dough and baked Chapathi. The work on the

process for the preparation of quick cooking Rice with increased yield,

reduced processing cost has been reported (Ramesh, 2000).

A review of the status of machinery for Indian traditional foods and

the need for mechanization with emphasis on reduced processing cost

with hygiene for the Indian food machinery manufacturers has been

presented (Ramesh, 2004).

Data on thermal properties of food products are needed to

understand their thermal behavior and to control heat transfer processes.

Knowledge of thermal properties is essential for mathematical modeling

and computer simulation of heat and moisture transport (Rask, 1989;

Sablani et al., 1998). Inspite of many reviews and books, data are not

available for many food products and needs to be generated.

24

Since most foods are hygroscopic in nature, one should consider

how strongly they bind water, for instance, moistures-solid interaction

during drying (Wang and Bernnam, 1992). The main parameter that

significantly influences the thermal properties of the bulk of food is the

moisture content. This is because the thermal properties of water are

markedly different from those of other components (Proteins, fats,

carbohydrates and air).

Presence of water also causes a strong temperature dependence

of thermal properties. A general review on thermal properties of food has

been brought out by Mohesnin (1980). The thermal properties of variety

of grains (Polley, et al., 1980), potato (Lamberg and Hallstorm, 1986),

dough and bakery products (Rask, 1989) have been reported.

The properties of particulate foods are more difficult to predict, due

to their variable heterogeneous structure and porosity (Wallapapan, et al.,

1986). Therefore, experimental measurements are especially important

for this class of food products.

In situations where heat transfer occurs at an unsteady state,

thermal diffusivity () is more relevant. The value of determines how

fast heat propagates through a material; higher values indicate rapid heat

diffusion. The of a material is defined as the ratio of the heat capacity

of the material to conduct heat divided by its heat capacity to store it

(McCabe, et al., 1995; Charm, 1971; Heldman and Singh, 1993; Perry

and Green, 1984).

The objection to steady state analysis is the long time required to

attain the steady state conditions, which in turn lead to changes in

25

compositions during measurement, migration due to temperature

difference across the material for a long period of time. Generally,

measurement of thermal properties require sophisticated and expensive

equipment (Urbicain and Lozano, 1997).

The transient method has been successfully applied to the

measurement of thermal conductivity of various food products such as

pigeon pea (Shepherd and Bhradwaj, 1986).

Polley, et al., (1980) have compiled data on specific heat (Cp) of

vegetables and fruits. Gupta (1990) reported the specific heat (Cp) of

unleavened flat bread (Chapathi) and other foods as well. Lamberg and

Hallstrom, (1986) have reported specific heat (Cp) over the temperature

range of 20 to 90C and a moisture range of 8 to 85% (wet bulb) of

freeze-dried Brintje potato. The specific heat is often measured using the

method of mixing, adiabatic calorimeter, differential scanning calorimeter

(DSC) and differential thermal analysis (DTA). The DSC techniques have

been vividly discussed by Callanan and Sullivan (1986). The guarded hot

plate method can also be used for measurement of specific heat (Cp).

Design of Traditional Food Machinery

The design problem can be best approached through a

combination of theory, modern knowledge of materials, awareness of the

limitations and practicability of various production methods as discussed

earlier. Various steps involved in the design process could be

summarized as a) the aim of the design, b) preparation of the simple

schematic diagram, c) conceiving the shape of the unit/machine to be

26

designed, d) preliminary strength calculation, e) consideration of factors

like selection of material and manufacturing method to produce most

economical design, f) mechanical design and preparation of detailed

manufacturing drawing of individual components and assembly drawing.

The selection of the most suitable materials for a particular part

becomes a tedious job for the designer. This is partly because of the large

number of factors to be considered which have bearing on the problem.

This is also because of the availability of very large number of materials

and alloys possessing most diverse properties from which the materials

has to be chosen. With the development of new material, a good

knowledge of heat treatment of materials which modifies the properties of

material to make them most suitable for a particular application is also

very important.

The material selected must posses the necessary properties for the

proposed application. The various requirements to be satisfied are weight,

surface finish, rigidity, ability to withstand environmental stress, corrosion

from chemicals, service life, reliability etc. The four types of principal

properties of material decisively affect their selection, namely, physical,

mechanical, chemical and ease of machining.

The thermal and physical properties concerned are co-efficient of

thermal expansion, thermal conductivity, specific heat, specific gravity,

electrical conductivity and magnetic property. The various mechanical

properties are strength in tensile, compressive, shear, bending, torsion

and fatigue as well as impact resistances. The properties concerned with

the manufacture are the weldability, castability, forgeability, deep drawing

27

etc. The various chemical properties concerned are resistance to acids,

oxidation, water, oils etc.

For longer service life, the parts are to be dimensioned liberally to

give reduced loading and due consideration given to its resistance to

thermal, environmental and chemical effects and also to wear. Stainless

steel, an iron base alloy is manufactured in electric furnace. It has a great

resistance to corrosion. The property of corrosion resistance is obtained

by adding chromium or chromium and nickel together. Selection of

material for food processing machinery is an added task for the designer.

For most of the food applications stainless steel is the preferred material

as the food material contains large amount of moisture and product is for

human consumption, needing hygiene. In certain cases, where acid foods

are handled, a special variety of stainless steel having very low carbon

content which has oxidation-resistant property is recommended.

Justification

The design of machinery for Indian traditional foods is a new and

specialized area involving extensive research and experimentation. Very

few organizations are involved in design and development of such food

processing machinery. Most of the food processing machinery available

in the country are imported and most of them are for processing of fruits,

vegetables, bakery products, confectionery and oils. A few industries have

adapted these imported food processing machinery for Indian foods.

Imported submerged fryer and the slicers are used for largescale

processing of Potato chips.

28

The machine design for Indian traditional foods is an exclusive

area for food/mechanical engineers and there are ample opportunities for

mechanization of these foods since it will not come under the purview of

multinational companies (MNCs).

The objective of the present work is to design and develop

machineries for Indian traditional foods incorporating the different

branches of engineering such as thermal, mechanical, chemical, electrical

and electronic and food engineering. The understanding of the physical,

thermal and engineering properties of foods is very important for the

design of any food-processing machine. Integration of the equipment

developed with the technology of food processing is also considered. In

the present work, design and development of traditional food machinery

such as Chapathi machine is taken up.

Section 2.2.0: Materials and Methods

Section 2.2.1: Materials

Whole-Wheat Flour (WWF):

Commercial medium hard wheat procured from the local market

was cleaned and ground in a disc mill to obtain whole-wheat flour. It

contains different fractions such as maida (soft core of wheat), bran, atta

and germ.

29

Atta (A):

Atta was obtained from International School of Milling Technology

Mill (CFTRI, Mysore). It is one of the fraction obtained from the roller flour

mill and do not contain fractions such as maida, germ and bran.

Section 2.2.2: Methods

Measurement of Temperature

A digital temperature indicator (ModelTFF 200, MakeEBRO,

Germany, PT-100, Range: -50 to 300 C) was employed to measure the

temperature of the hot plate as well as the product temperature. The

temperature indicator had a resolution of 0.1 C with a least count of 0.1 C.

Determination of Thermal Conductivity

Chapathi were baked on the hot plate by discharging a known

amount of dough of predetermined consistency (Venkateshmurthy, et al.

1998). The probe of the temperature indicator was positioned through a

hole at the center of the Chapathi disc to measure the product surface

temperature. Thermal conductivity was calculated from these test results

by using appropriate terms in equation (5) and (6).

Sieve Analysis of the Flour

Sieve analysis of the flour samples were carried out in a Buhler

Laboratory plan-sifter (Type MLU-300), using 200 g samples. The over

30

tailings on each sieve were weighed after 10 min of sieving and

percentages were calculated on a total flour weight basis.

Chemical Analysis

Flour moisture, gluten, ash and damaged starch were estimated by

standard AACC methods (1983).

Rheological Characteristics

Farinograph characteristics of Chapathi dough prepared in a

Hobart mixer were determined by transferring the dough equivalent to 50

g flour (14% moisture basis) to a 50 g mixing bowl of the Farinograph.

The dough was mixed for 10 min at 1:3 lever position and various

parameters like peak consistency, dough development time (DDT),

stability and elasticity were assessed from a farinogram in accordance

with the AACC methods (1983).

Extensograph characteristics of Hobart-mixed Chapathi dough

were measured with 100 g dough instead of generally used 150 g dough.

However, 50 g weight was placed on the dough hook, while stretching the

dough, to compensate for the lower dough weight. The extensograph

characteristics were measured as per the standard methods (AACC,

1983). Compliance and elastic recovery of the dough were measured

using a penetrometer (Sai Manohar and Haridasrao, 1992).

The consistency of the Chapathi dough was measured in RWAM

as per the method described earlier (Haridasrao, et al., 1987).

31

Hand Sheeting

For comparing the quality of machine-made Chapathi, about 35 g

dough was sheeted using a rolling pin and a rectangular frame with

adjustable height 1.5 mm as per the method described earlier

(Haridasrao, et al., 1986). The thickness as obtained in the Chapathi

sheet was maintained to the same thickness as obtained in the Chapathi,

sheeting device.

Baking of Chapathi

Baking of Chapathi was done on a hot plate, followed by puffing on

a gas flame as per the standard procedure (Haridasrao, et al., 1986).

Statistical Analysis

Statistical analysis of the data was carried out according to Duncan

New Multiple Range Test (Snedecor and Cochran 1968).

Section 2.2.3: Design of Machine

Chapathi Machine

The Chapathi machine as shown in Fig. 2.1 comprises of two

major sub-assemblies, namely, 1) Chapathi sheeting unit and 2)

Chapathi-baking unit. Both these units are integrated to produce Chapathi

continuously in largescale automatically. In order to protect the invention,

the machines are covered by three Indian patents.

32

1. Chapathi Sheeting Unit

The Chapathi sheeting unit consists of pneumatic extruder and a

dusting and cutting device as the main sub-assemblies as shown in Fig.

2.2.

Pneumatic Extruder

The pneumatic extruder is an important sub-assembly of the

Chapathi sheeting unit. The device as shown in Fig. 2.3 the extrusion is

based on compressed gas. The device comprises of a conical vessel,

having flanges at its top and bottom, with a provision for admitting

compressed gas. A plate having a slot, fixed gas tight on to the bottom of

the cylindrical vessel with suitable gasket. A pair of plates is bolted to the

bottom plate for varying the thickness of the extruded sheet. The cover

plates of the vessel may have additional means such as bolt and nut to

make it gas tight.

The rested (15 min) dough was transferred to the conical vessel of

Chapathi sheeting unit. The dough was extruded by compressed air under

air pressure (41 kg/cm2) through a slit adjusted to a width of 0.8 mm. The

air pressure was adjusted such that the rate of extrusion was maintained

constant at 800 mm per min. The circular-shaped discs are cut from

Chapathi dough.

The conical vessel has the drawback of cavitation, which led to the

escape of the compressed air and non-uniform extrusion.

33

Improved Pneumatic Extruder

In order to overcome the above drawbacks, an improved

pneumatic extruder, as shown in Fig. 2.4 was developed

(Venkateshmurthy, et al., 2000). The improved device has the ability for

the extrusion of dough into sheet or strands of uniform thickness at a

constant rate.

A Device for Dusting and Cutting of Dough Sheet

The design relates to a device for dusting and cutting of dough into

any geometrical shape as shown in Fig. 2.5. Geometrical shapes

obtained by using the device are of uniform dimension and obtained

continuously. The dough employed are wheat dough, urdh dough. The

invention is therefore useful as a sub-assembly for the Chapathi-sheeting

unit for dusting and cutting of Chapathi.

2. Chapathi Baking Unit:

The cross sectional view of the Chapathi-baking unit is shown in

the Fig. 2.6. The Chapathi discs are baked on a set of hot plates on both

the sides. The oil is applied on both sides through an oiling device. The

machine has the provision for varying/controlling of the baking time/

temperature through an AC drive and temperature controller respectively.

The baked Chapathi are discharged through a discharge chute.

34

Preparation of Chapathi Dough

Dough was prepared from both whole-wheat flour as well as Atta.

It was prepared by mixing 3 kg of flour and water for 3 min in a Hobart (N-

200) mixer at low speed. Water amounting to 1.95 L and 1.74 L was used

in the case of whole-wheat flour and atta, respectively. The temperature

of the mixed dough was adjusted to 27 C by altering the temperature of

water. The consistency of the dough was measured after 15 min of

relaxation time using Research Water Absorption Meter (RWAM).

The wheat flour used for standardization of the pneumatic extruder

was found to have initial moisture of 11.4% max. From the preliminary

experiments it was found that optimum added moisture to be 67% for the

pneumatic extrusion. Thus the total moisture of the wheat dough/Chapathi

disc is 78 %. The moisture loss during baking is in the range of 19 ~ 29 %

of the initial weight of the Chapathi disc.

Energy Balance

The liquid petroleum gas (LPG) a blend of butane and propane in

the ratio of 60:40 (commercially available gas is used as heat source).

From the theoretical calculation the requirement of the LPG for supplying

the required heat to the hot plate is estimated to be around 640 g,

considering the heating value/calorific value of the LPG as 11,642 Kcal/

kg. It was reported that 30 kg of air is required for complete combustion

of the LPG. The circular burner is provided with a gas mixing tube (for

mixing of air and LPG for complete combustion), which balances the air

fuel ratio of 30:1 and the outlet is provided with holes of 3.5 mm diameter,

35

where the actual flame heats the circular hot plate. A diffuser tube is

provided inside the burner to lower the pressure of the LPG (which is at

higher pressure inside the filled cylinder) and also its uniform distribution.

From the preliminary experiments, it was found that the baking time

of the Chapathi depends on the thickness of the disc and the moisture

content of the dough disc and found to be 60 s for each side. The

rotational speed of the Chapathi-baking unit is designed for a total baking

time of 120 s and the speed variator has the provision even for the

incremental variations.

From the large-scale trial runs, it was noticed that the actual

consumption of the LPG was found to be around 1.25 Kg, which is more

than the theoretical estimates. The variation in consumption of the gas

can be attributed to the heat loss occurring in different parts of the baking

unit and the major heat loss in the baking unit is from the hood. Thermal

efficiency of the Chapathi baking unit is estimated to be around 51%.

Section 2.3.0: Results and Discussion

Section 2.3.1: Design and Development

1. Chapathi Sheeting Unit

The Chapathi sheeting unit, as shown in Fig. 2.2 comprises of a

pneumatic extruder, dusting sub-assembly, circular moving cutters,

cutting roller, return conveyor, diverters/chutes and main drive. The

concept of extrusion of food material using compressed air has been tried

out for the first time. The device is useful for the extrusion of any dough,

36

particularly farinaceous dough, into sheet or strands. The sheet or strands

extruded using the device are uniform in thickness and extruded

continuously. The dough employed are wheat dough, urd dough and

invention is useful as an accessory to Chapathi machine. The pneumatic

extruder is housed on to the main frame of the Chapathi sheeting unit. In

order to reduce the stickiness of the extruded sheet, two dusting sub-

assemblies are provided for dusting of the dough sheet on both the sides.

The extruded sheet is allowed to fall on to the moving circular

cutters/plates, where in the cutting rollers cuts the rectangular sheet into

circular discs. The circular discs are transferred to the baking unit and the

uncut extra sheet is reused for further sheeting.

Pneumatic Extruder

As discussed earlier, the pneumatic extruder is an important sub-

assembly of the Chapathi-sheeting unit. The device as shown in Fig. 2.3

the extrusion is based on compressed gas. The device comprises of a

conical vessel, having flanges at its top and bottom, with a provision for

housing suitable gaskets a cover plate having a quick fix coupling on its

top at its center for admitting compressed gas into the vessel. The bottom

of the cover plate being provided with a gas deflector for preventing the

gas directly impinging on the dough mass contained in the vessel. The

cover plate rests over the flange at the top of the vessel and in between

the cover plate and the flange, a suitable gasket being provided to make

the arrangement gas tight. A plate having a slot, fixed gas tight on to the

bottom of the cylindrical vessel with suitable gasket. A pair of plates is

37

bolted to the bottom plate for varying the thickness of the extruded sheet.

The cover plates of the vessel may have additional means such as bolt

and nut to make it gas tight. The conical or trapezoidal shape of vessel is

preferable in the case of dough for making Chapathi because the hold-up

volume of the dough is less, when compared to a cylindrical one and

leakage of the compressed gas is reduced as the dough forms a wedge in

the conical or trapezoidal vessels.

However the pneumatic extruder discussed above was found to have

the following drawbacks.

Due to the conical shape of the vessel the rate of extrusion will vary, as extrusion proceeds.

The force applied during extrusion also varies as the cross-sectional area continuously changes, as extrusion proceeds.

Due to non-uniform flow of the dough inside the vessel during extrusion, cavitation of the dough occurs.

The frictional resistance offered for the flow of the dough is more. The cavitation of the dough during extrusion abruptly ends the

process of extrusion due to release of the compressed air.

Large amount of dough is leftover in the vessel. The dough sheet had poor surface finish. Variations in the rate of extrusion of the dough leading to non-

uniform sheet of dough.

38

Improved Pneumatic Extruder

An improved pneumatic extruder was developed in order to

overcome the above drawbacks (Venkateshmurthy, et al., 2000). The

main object of the improved device for extrusion of dough into sheet or

strands based on the principle of pneumatic extrusion in a cylindrical

vessel, which obviates the above noted drawbacks. The improved device

has the ability for the extrusion of dough into sheet or strands of uniform

thickness, at a constant rate. The invention is also to provide a device

wherein the force applied during extrusion remains constant. Further there

is uniform flow of the dough inside the vessel during extrusion wherein the

cavitation of the dough during extrusion is avoided, which enables a

continuous operation of sheeting thereby making leftover dough in the

vessel negligible.

The improvements incorporated into the pneumatic extruder as

shown in Fig. 2.4, overcomes most of the drawbacks of the earlier design

employed for the production of sheet.

This improved device consists of a cylindrical vessel, having

flanges at its top and bottom and the cover plates have projections for

housing suitable gaskets. The top cover plate has a quick fix coupling on

its top for allowing the compressed gas into the vessel. The cylindrical

vessel is provided with a sliding piston with suitable handle and an air

vent. The piston is provided with a rubber O ring to make the device leak

proof. In between the cover plate and the flange, a suitable gasket being

provided which rests on the flange to make the arrangement gas tight. A

39

plate having a slot is fixed to the bottom of the cylindrical vessel with a

suitable gasket. A pair of strips is bolted to the bottom plate. The cover

plates and top portion of the vessel may have additional means such as

bolt and nut to make the cylindrical vessel gas tight.

The material of construction should withstand the pressure at

which the improved device is operated. Particularly in the case of sheeting

of Chapathi the pressure used is 2.5 to 6 bars. The bottom cover plate

has a blind slot at its center. This slot may be preferably of 200 mm length

and 8 mm width. Tapped holes are provided on the bottom cover plate, to

attach suitable strips for varying the size and shape of the extruded sheet.

The strips may also be of the same material as that of the cylindrical

vessel and preferably stainless steel. Such an arrangement will be useful

to control the thickness of the extruded sheet. This improved device can

be attached to a cutting unit, which can produce Chapathi,, of different

shapes such as circle, triangle, square, rectangle etc. This should not be

construed to restrict the use of the device for making Chapathi only. It is

to be noted that the device can be used for making other similar food

articles such as Papads, Noodles etc.

The working of the device is explained below with particular

reference to sheeting of Chapathi.

Dough out of whole wheat flour or atta with an initial moisture

content of around 8-12 % is prepared by adding water of about 50 ~ 68 %

and 5 % of fat (groundnut oil) and 3 % common salt. Ingredients are

mixed in a planetary mixer for about 3 min. The dough is covered with a

polyethylene sheet to prevent evaporation and allowed to relax for about

40

15 - 20 min. Then the dough is charged into the extruder vessel and admit

compressed air or nitrogen or carbon dioxide gas into the vessel at a

pressure of around 2.5 - 6 bar (g). Sheet will be extruded at a rate of

about 800 mm/min. Sheet width would be 175 mm as the slit on the

bottom plate is adjusted to 180 mm and thickness around 0.8-1.2 mm.

This extruded dough sheet is allowed to fall on the slat cutter of a

Chapathi-sheeting unit as described earlier. The linear velocities of dough

sheet and slat cutter are synchronized. The bottom and topside of the

dough sheet is dusted with dry flour to avoid sticking of dough sheet to

slat cutter and cutting roller. When the dough sheet is spread on the slat

cutter and the slat cutter passes beneath the Teflon roller, the circular

discs are formed in the dimple of the slat cutter. The uncut dough sheet is

transferred on to a return conveyor and collected in a tray. It is possible to

vary extrusion rates easily by controlling the air pressure. Air pressure can

also take care of the variations in the rheological characteristics of the

dough.

The main advantages of this invention are:

The dough inside the cylindrical extruder is isolated from the compressed air by a piston.

The frictional resistance for the smooth flow of the dough is minimum.

There is no cavitation during extrusion and this is due to the presence of piston.

41

A Device for Dusting and Cutting of Dough Sheet

The device for dusting and cutting of dough into any uniform

geometrical shape as shown in Fig. 2.5.

This device comprises of a geared motor fixed to a frame, slat

cutter assembly, having been bolted on a chain conveyor. The edge of the

slat cutter having been tapered to an angle of 15~40 and the chain

conveyor being driven by a pair of sprockets. The shaft in turn housed in

antifriction bearings. The sprocket assembly being driven by the geared

motor through a roller chain. The roller assembly consisting of roller and

bearing plates being fixed to the top of the frame. The roller being housed

inside the plate, which imparts the roller, a 6 degree freedom. The roller

being placed such that it rests on the slat cutter and the dough sheet is

formed into geometrical shapes because of the self-weight of the roller.

Two dusting assembly being located, one before the roller for spraying

flour dust on the conveyor and the other after the roller for spraying on top

of the dough sheet. The dusting assemblies consisting of a tube closed at

both ends fitted with a sieve at the bottom and a hopper on its periphery.

A rotary brush is operating within the closed tube, capable of spraying dry

flour when the rotary brush passes against the perforated sieve. A return

conveyor is provided for transferring the uncut portion of the dough sheet

for reuse. The cut circular Chapathi discs are collected in a tray through

the perforated chutes. All the above said assemblies are mounted on an

angle frame, which is covered on all its sides. The whole assembly is

mounted on swivel castors for easy movement of the unit to the required

42

place. The Chapathi discs are collected and fed on to the Chapathi baking

oven.

Chapathi-Baking Unit

The Chapathi baking unit, as shown in Fig. 2.6 is based on the

concept of rotating hot plates. The Chapathi disc formed by using the

pneumatic sheeting unit is transferred to the first rotating hot plate through

a chute/guide. The disc after baking on one side on the first hot plate to

the predetermined time of 50 s and is transferred to the second hot plate.

During the transfer of the Chapathi disc from the first hot plate to the

second hot plate, it turns over to the other side during its free fall. The

Chapathi disc is allowed to bake on the second hot plate to the pre-set

time of approximately 50 s. Oil is dispensed on both sides of the Chapathi

disc through an oi