Banana Quitosano

International Journal of Fruit Science, 11:119–135, 2011Copyright © Taylor & Francis Group, LLCISSN: 1553-8362 print/1553-8621 onlineDOI: 10.1080/15538362.2011.578512

Banana Fruit Ripening as Influencedby Edible Coatings

NEETA B. GOL and T. V. RAMANA RAOB R D School of Biosciences, Sardar Patel University, Vallabh Vidyanagar,

Gujarat, India

The effects of chitosan 1% and 1.5%, calcium chloride (CaCl2)1% and 1.5%, chitosan 1% + gibberellic acid 100 ppm, chitosan1.5% + gibberellic acid 100 ppm, jojoba wax, and glycerol (98%)coatings were evaluated on the shelf life and postharvest qualitycharacteristics of banana fruits stored at 34 ± 1◦C and 70–75%relative humidity, while uncoated fruits served as a control. Thecoatings of chitosan, chitosan + gibberellic acid, and jojoba waxdelayed the changes in the weight loss percentage, decay percent-age, total soluble solids, pH, titrable acidity, sugar accumulation,pigment degradation, and ascorbic acid compared to uncoatedones. Further, the least disease incidence was found to occur inthe banana fruits treated with chitosan and chitosan + gibberellicacid. Hence, it can be concluded that coating with chitosan andchitosan + gibberellic acid has the potential to control decay per-centage, prolong the shelf life, and preserve valuable attributes ofbanana. Calcium chloride and glycerol coatings neither showedany potential to control disease incidence nor prolong the storagelife and preserve valuable attributes of banana fruit.

KEYWORDS banana, edible coating, postharvest, shelf life,quality characteristics

INTRODUCTION

Banana (Musa spp.) is the most widely cultivated and consumed fruit inthe tropical and subtropical regions of the world where they constitute amajor staple food crop for millions of people (Deka and Choudhury, 2006).

Address correspondence to T. V. Ramana Rao, B R D School of Biosciences, Sardar PatelUniversity, Vallabh Vidyanagar, Gujarat 388 120, India. E-mail: [email protected]

119

120 N. B. Gol and T. V. Ramana Rao

India is the largest producer of fruits in the world and banana tops the listwith respect to production and area of cultivation (TIFAC Report cited inSurendranathan et al., 2004). Bananas contain nutrients in more balancedproportion than many other fruits. They have nearly all the essential nutri-ents, including minerals and vitamins (Islam et al., 2001). Bananas are uniquedue to their high calories and nutritive values. As compared to apples,they contain five times more vitamin A and iron, four times more protein,three times more phosphorus, twice the carbohydrates, and the other vita-mins and minerals (Gasster, 1963). They are useful for patients with pepticulcers, for treatment of infant diarrhea, celiac disease, and colitis (Robinson,1996). They are also ideal for patients suffering from gout, arthritis, kid-ney disorders, blood pressure, and heart problems (Stover and Simmonds,1987).

In many cases, bananas are transported from localities of productiongreat distances for marketing and consumption. Bananas, being a climac-teric fruit, have a very short storage life. They are highly perishable andare, therefore, susceptible to several diseases resulting in extensive posthar-vest losses (Maqbool et al., 2010). In turn, longer shelf life would enhancetrade opportunities between nations by extending time constraints underwhich fresh produce must be delivered to more distant geographic marketsor by allowing the use of slower and less expensive modes of transportation(Kader, 1986). But due to absence/non adoption of proper postharvest man-agement practices, the postharvest loss of bananas is highest (22%) amongall the fruits (Deka and Choudhury, 2006). Reduction of postharvest lossesreduces cost of production, trade and distribution, lowers the price for theconsumer, and increases the farmers’ income.

The extension of fruit shelf life is an important goal to be attained. Manystorage techniques have been developed to extend the marketing distanceand holding periods for commodities after harvest. Different preservationmethodologies have been studied. One method of extending postharvestshelf life is the use of the edible coatings. Today, use of edible coatingsis a common issue that is beneficial to protect nutrients of food, espe-cially fruits and vegetables, and provide a long durability (Raheleh et al.,2008). Edible coatings have long been known to protect perishable foodproducts from deterioration by retarding dehydration, suppressing respira-tion, improving textural quality, helping retain volatile flavor compounds,and reducing microbial growth (Debeaufort et al., 1998). The objective ofthis study was to elucidate the effects of edible coatings, such as chitosan[alone and in combination with gibberellic acid (GA3)], calcium chloride(CaCl2), jojoba wax, and glycerol on physiological and biochemical changesin harvested banana fruit with a view to optimization of this postharvesttechnology for green life extension.

Banana Fruit Ripening as Influenced by Edible Coatings 121

MATERIALS AND METHODS

Fruit Materials

For the present study, hands of mature green bananas were obtained from alocal farm in Vallabh Vidyanagar, Gujarat, India. Hands were cut into fingers,and dipped for 3 min in sodium-hypochlorite (500 ppm) fungicide solutionto control postharvest diseases, and then were allowed to air dry. Fruits wereselected for freedom from visual defects and uniformity of shape, color, andsize. Subsequently, these banana fruits were grouped into 8 experimentalsets with 20 fruits per set and a control set of 20 fruits. The postharvesttreatments (edible coatings) viz. chitosan 1% (T1), chitosan 1.5% (T2), CaCl21% (T3), CaCl2 1.5% (T4), chitosan 1% + GA3 100 ppm (T5), chitosan 1.5% +GA3 100 ppm (T6), glycerol (T7), jojoba wax (T8), and (uncoated) control(T9) were given for 10 min. After the treatment, the fruits were air dried at anambient temperature for 30 min in an attempt to reduce possible chemicalinjury.

The treated banana fruits of experimental as well as control sets weresubjected for the following physiological and biochemical analyses at thebeginning of the experiment (i.e., 0 days) and after 5 and 10 days of storagein the laboratory with the average maximum and minimum temperature ofit at 34 ± 1◦C and relative humidity 70–75%.

Weight Loss Percentage (WLP)

The WLP of banana fruit samples was calculated by considering the differ-ences between initial weight and final weight of currently tested bananafruits divided by their initial weight.

Decay or Rotting Percentage

The decay or rotting of the stored banana fruits was determined by theirvisual observations. Decayed fruits (physiological and microbial decay) werediscarded in each sample and decay percent was recorded.

Shelf Life

The shelf life of these banana fruits was calculated by counting the daysrequired for them to attain the last stage of ripening, but up to the stagewhen they remained still acceptable for marketing.


Total Soluble Solids (TSS), pH, and Titrable Acidity (TA)

The TSS content of the fruit was determined by using a refractrometer (AtagoCo., Tokyo, Japan). A homogenous sample was prepared by blending thebanana flesh in a blender. The sample was thoroughly mixed and a fewdrops were taken on the prism of the refractometer and a direct readingwas taken by reading the scale in the meter as described in AOAC (1994).The pH of the fruit samples was determined as per the method describedby AOAC (1994), while the titrable acidity (expressed as citric acid %) wasdetermined by titrating 5 ml of juice with 0.1 N sodium hydroxide, usingphenolphthalein as an indicator (Mazumdar and Majumder, 2003).

Biochemical Analysis

The total soluble sugars and starch content were determined by followingthe anthrone method, while the dinitrosalicylic acid method was followedfor the reducing sugars and non reducing sugar content (Thimmaiah, 1999).The quantitative analyses of pigments, such as total chlorophylls (total chl.),chlorophyll ‘a’ (chl. ‘a’), chlorophyll ‘b’ (chl. ‘b’), and total carotenoids, werecarried out as per the methods described by Wang et al. (2005). Ascorbicacid (vitamin C) content was determined by using the titrimetric methodwith the titration of filtrate against 2, 6-dichlorophenol indophenols, and theresults of vitamin C content were expressed as mg.100 g−1 (Mazumdar andMajumder, 2003).

Statistical Analysis

All the performed analyses were carried out in triplicate and the standarddeviation was calculated. The experimental design was a completely ran-domized design with three replicates. Analysis of variance (ANOVA) wasused to detect treatment effect. Mean separation was performed by usingleast significance difference (LSD) at the P < 0.05 level. The data wereanalyzed using Duncan’s multiple range test (Bliss, 1967).

RESULTS AND DISCUSSION

Weight Loss Percentage

Result shows the change of WLPs of coated and uncoated banana (control)during the storage period (Table 1). Coating process caused a significantdecrease (P < 0.05) in WLPs as compared with the control samples. All thetreatments, except T7, showed a reduction in WLPs compared to that of thecontrol fruits. The control samples had significantly (P < 0.05) higher WLP

TAB

LE1

Effec

tofEdib

leCoat

ings

and

Thei

rCom

bin

atio

ns

With

Diffe

rentChem

ical

son

Wei

ghtLo

ssPer

centa

ges

(WLP

S)an

dD

ecay

Per

centa

geofB

anan

aFr

uit

During

Stora

geat

34±

1◦ C

Tre

atm

ents

Stora

geper

iod

(day

)T1

T2

T3

T4

T5

T6

T7

T8

T9

LSD

(P<

0.05

)

WLP 0

0.00

g0.

00g

0.00

g0.

00g

0.00

g0.

00g

0.00

g0.

00g

0.00

g0.

005

3.76

±0.

74c

4.78

±0.

66c

8.31

±1.

37b

6.86

±0.

92b

4.43

±0.

58c

3.21

±0.

58c

7.63

±1.

41b

3.75

±0.

53c

10.3

5±

0.99

a1.

5759

109.

67±

1.01

d6.

20±

0.36

f15

.02

±0.

73b

12.2

0±

1.41

c6.

00±

0.44

f7.

18±

0.62

ef21

.27±

1.12

a7.

83±

1.02

e15

.98

±0.

71b

1.52

07D

ecay

per

centa

ge0

0.00

f0.

00f

0.00

f0.

00f

0.00

f0.

00f

0.00

f0.

00f

0.00

f0.

005

7.03

±1.

76e

5.58

±0.

53e

21.0

0±

1.00

c23

.50±

1.32

b5.

45±

0.40

e6.

83±

0.68

e30

.50±

0.50

a9.

50±

0.50

d31

.33

±1.

26a

1.69

8310

13.1

7±

1.61

d10

.25

±0.

25e

38.2

7±

1.55

b35

.33±

0.29

c9.

90±

0.56

e13

.00

±1.

80d

39.1

7±

0.76

ab11

.50

±1.

32de

40.6

7±

0.76

a1.

9492

Mea

ns

with

the

sam

ele

tter

sw

ithin

row

sar

enot

sign

ifica

ntly

diffe

rent

atP

<0.

05usi

ng

LSD

.Eac

hva

lue

isth

em

ean

for

thre

e(n

=3)

replic

ates

.The

valu

esre

pre

sente

d(a

–g)

inth

ere

sults

indic

ate

the

range

from

hig

her

tolo

wer

rank.

T1—

chito

san

(1%

);T2—

chito

san

(1.5

%);

T3—

calc

ium

chlo

ride

(1%

);T4—

calc

ium

chlo

ride

(1.5

%);

T5—

chito

san

(1%

)+

gibber

ellic

acid

(100

ppm

);T6—

chito

san

(1.5

%)+

gibber

ellic

acid

(100

ppm

);T7—

glyc

erol(

98%

);T8—

jojo

ba

oil;

T9—

control

(unco

ated

).

123


(15.98%) after 10 days of storage, while banana samples coated with chi-tosan, chitosan + GA3, CaCl2, and jojoba wax had significantly (P < 0.05)lower WLP values. The weight loss in banana during ripening might be dueto substrate loss by respiration and loss of water through various physio-logical mechanisms (Islam et al., 2001). This reduction in weight loss wasprobably due to the effects of these coatings as a semi-permeable barrieragainst oxygen, carbon dioxide, moisture, and solute movement, therebyreducing respiration, water loss, and oxidation reaction rates (Baldwin etal., 1999). The obtained results are in accordance with the findings of Garciaet al. (1998) who reported that the chitosan film formed on the surface of thefruit delayed migration of moisture from the fruit into the environment, thusreducing weight loss during storage. The T2 (chitosan 1.5%) treatment wasobserved to prevent weight loss more than that of other tested treatmentsthroughout the storage period but was less than that of the T5 (chitosan +GA3) treatment. The combined treatment (i.e., T5 and T6) was clearly effec-tive in conferring a physical barrier to moisture loss and, therefore, retardingdehydration and fruit shriveling. In this experiment, the glycerol and CaCl2coating was the least effective in reducing weight loss. CaCl2 treatmentsincreased weight loss that was due to osmotic potential. Earlier studies bysome investigators also indicated that postharvest application of Ca2+ accel-erated ripening of ‘Cavendish’ bananas (Willis et al., 1982a; Huddar et al.,1991).

Decay Percentage

Data summarized in Table 1 show the changes in decay percentage values ofcoated and uncoated bananas (control) during the storage period. Coatingssignificantly (P < 0.05) reduced the decay percentage as compared to thatof control samples during the storage period. Decay percentage of controlsamples at the end of storage period was approximately four to five timeshigher than that of the banana fruits coated with chitosan, chitosan + GA3,and jojoba wax. Among all the presently tested treatments, T2 (i.e., 10.3%)and T5 (i.e., 9.9%) treatments were superior in controlling the decay per-centage. Chitosan in combination with GA3 (T5) significantly reduced thedecay level, i.e., 9.9% compared to all other treatments and control samples.This is consistent with the reports that chitosan has antifungal propertiesagainst several postharvest pathogens (Jiang and Li, 2001). El-Ghaouth et al.(1992a) suggested that chitosan induces chitinase, a defense enzyme, andcatalyzes the hydrolysis of chitin, a common component of fungal cell walls,thus preventing the growth of fungi on the fruits. The results of the presentstudy show that the banana fruits treated with jojoba wax had a lower decaypercentage, i.e., 11.5% after 10 days of storage. Similar results were obtainedby Ahmed et al. (2007) in orange fruit that was coated with jojoba wax andhad lower decay percentage compared to the control fruits.


Shelf Life

The shelf life of banana fruit has been extended significantly (P < 0.05) withsome of the treatments tested in the current study (Table 2). The bananafruits treated with the T6 treatment were found to extend their shelf life tothe maximum duration of 17.2 days as compared to that of other presentlytested treatments (Table 2). The treatment of 1% and 1.5% of chitosan causedthe extension of shelf life of banana fruits tested in the current study by 15.3and 16.2 days, respectively, as compared (i.e., 11.3 days) for fruits of the con-trol set (Table 2). These results also support the view of Zhang and Quantick(1998) who reported that the application of a chitosan coating improved thequality and storability in strawberries and raspberries. The positive effect ofa chitosan coating on storage life could probably be due to modifying theatmosphere within as in modified atmosphere (MA) storage. The depolymer-ization process of metabolism substrates is possibly influenced by the MAcreated inside fruits. The MA created can, therefore, delay ripening by delay-ing ethylene production and by reducing the level of internal oxygen andconsequently prolonging the storage life of fruits (El-Ghaouth et al., 1992b).Among the tested postharvest treatments, the fruits treated with chitosan andGA3 (T6) exhibited longer shelf life and reduced spoilage (Table 2). Raoand Chundawat (1988) suggested that postharvest dipping of fruits in GA3

delayed the conversion of starch to sugars and reduced peroxidase activityand ethylene production. In the present study, calcium treatments showed adepressing impact on the shelf life. Studies carried out by other investigatorsalso indicate that postharvest application of Ca2+ accelerated ripening of‘Cavendish’ bananas (Willis et al., 1982a; Huddar et al., 1991). The hastenedcolor development may be linked to faster achievement of senescence lead-ing to shorter shelf life. A previous study on bananas showed a tendencytowards a negative correlation of lesion diameter of anthracnose and fruitfirmness (Perera et al., 1999). These results appear to suggest that firmnessreduction observed in Ca2+-treated bananas may develop a susceptibility toanthracnose and, hence, reduction of shelf life.

Total Soluble Solids

Changes in the TSS of bananas over the storage time are shown in Table 2.The TSS of control fruit increased with storage time, while the banana fruitscoated with chitosan, chitosan + GA3, and jojoba experienced a slowerincrease during the 10 days of storage. Data showed that control sam-ples without coating treatments had significantly (P < 0.05) higher levelsof TSS with 20.7% at 10 days of storage period. TSS values of banana treatedwith T1, T2, T5, T6, and T8 after 10 days of storage were approximately1.3, 1.4, 1.4, 1.5, and 1.5 times lower, respectively, than the TSS values ofcontrol samples without coating. The concentrations of free sugars progres-sively increased with storage; this increase was quite markedly delayed by

TAB

LE2

Effec

tof

Edib

leCoat

ings

and

Thei

rCom

bin

atio

nW

ithD

iffe

rent

Chem

ical

son

Shel

fLi

fe(D

ays)

and

Tota

lSo

luble

Solid

s(T

SS)

of

Ban

ana

During

Stora

geat

34±

1◦ C

Tre

atm

ents

Stora

geper

iod

(day

)T1

T2

T3

T4

T5

T6

T7

T8

T9

LSD

(P<

0.05

)

Shel

flif

e(d

ays)

Atth

een

dof

the

stora

geper

iod

15.2

6d16

.16b

11.2

3f12

.13e

16.3

6b17

.16a

11.4

0f15

.66c

11.3

0f0.

3975

TSS

(%)

011

.2±

0.8f

11.2

±0.

8f11

.2±

0.8f

11.2

±0.

8f11

.2±

0.8f

11.2

±0.

8f11

.2±

0.8f

11.2

±0.

8f11

.2±

0.8f

1.37

425

14.3

4±

0.59

c14

.01

±0.

02c

17.6

7±

0.58

b18

.68

±0.

59ab

12.3

6±

0.56

d12

.68

±0.

56d

18.6

7±

1.15

ab13

.01

±0.

01d

19.0

3±

0.04

a0.

9878

1016

.33

±0.

58c

15.0

2±

0.03

d20

.17

±0.

76ab

19.6

7±

0.58

b14

.69±

0.54

de

14.0

2±

0.03

e19

.68

±0.

59b

14.0

2±

0.03

e20

.7±

0.61

a0.

8590

Mea

ns

with

the

sam

ele

tter

sw

ithin

row

sar

enotsi

gnifi

cantly

diffe

rentat

P<

0.05

usi

ng

LSD

.Eac

hva

lue

isth

em

ean

for

thre

e(n

=3)

replic

ates

.The

valu

esre

pre

sente

d(a

–f)

inth

ere

sults

indic

ate

the

range

from

hig

her

tolo

wer

rank.

T1—

chito

san

(1%

);T2—

chito

san

(1.5

%);

T3—

calc

ium

chlo

ride

(1%

);T4—

calc

ium

chlo

ride

(1.5

%);

T5—

chito

san

(1%

)+

gibber

ellic

acid

(100

ppm

);T6—

chito

san

(1.5

%)

+gi

bber

ellic

acid

(100

ppm

);T7—

glyc

erol

(98%

);T8—

jojo

ba

oil;

T9—

control(u

nco

ated

).

126


chitosan, chitosan + GA3, and jojoba coatings. This was probably due tothe semi-permeable chitosan film, which formed on the surface of the fruits,causing the modification of internal atmosphere and the endogenous CO2

and O2 concentrations of the fruit, thus retarding ripening as shown by Baiet al. (1988). Other reports indicated a slow rise in TSS of mango and bananatreated with chitosan (Kittur et al., 2001), which might be due to chitosan’seffect on slowing down the ripening, respiration rise, and metabolism pro-cesses of the fruits. The combined treatment of chitosan and GA3 had agreater effect in reducing the TSS during storage compared to other testedtreatments. During the 10 days of storage, the least amount of TSS (i.e.,14.0%) was seen in the T6- and T8-treated banana fruits.

pH and Titrable Acidity

Uncoated (control) fruit was observed to have higher pH values comparedwith other coated fruits (Table 3). Chitosan 1.5% and chitosan (1.5%) + GA3

(100 ppm) coating proved to be significantly better (P < 0.05) in maintaininglow pH, compared to uncoated fruits and CaCl2-coated fruits. The combinedtreatment of chitosan and GA3 showed the changes in pH effectively, delay-ing fruit ripening and senescence. All the coated fruits have shown lower pHcompared to that of uncoated fruits. The pH in both coated and uncoatedfruits increased, while their titrable acidity decreased significantly (P < 0.05)along with increased storage time (Table 3). These results are in accordancewith those reported by Garcia et al. (1998) that the decrease of acidity duringstorage demonstrated fruit senescence. The change in pH is associated witha number of reasons; it might be due to the effect of coating on the bio-chemical condition of the fruit and slower rate of respiration and metabolicactivity (Jitareerat et al., 2007). Coating slowed the changes of pH and TAby effectively delaying fruit senescence. The higher level of TA in the fruitscoated with chitosan and the combination with GA3 (Table 3) may be dueto a protective O2 barrier or reduction of O2 supply to the fruit surface thatinhibited the respiration rate (Jiang and Li, 2000). Increased activity of citricacid during ripening or reduction in acidity may be due to their conversioninto sugars and their further utilization in the metabolic processes of thefruit. The chitosan coating treatment [i.e., T1 (4.4%) and T2 (4.2%)] showedsignificantly (P < 0.05) higher amounts of TA than that of chitosan + GA3

[i.e., T5 (3.3%) and T6 (3.2%)] during 10 days of storage. Slowing down thebanana ripening by means of coating (chitosan and jojoba) and GA3 causinginhibition of enzyme activity could be the reason for delay in the use oforganic acids in the enzymatic reactions of respiration. This result was con-sistent with reports of Garcia et al. (1998) and Zhang and Quantick (1998)who reported that TA of chitosan or starch-based coated strawberries keptunder cold storage decreased with time, but to a lesser extent than that ofuncoated fruit.

TAB

LE3

Effec

tofEdib

leCoat

ings

and

Thei

rCom

bin

atio

nW

ithD

iffe

rentChem

ical

son

pH

and

Titr

able

Aci

dity

(TA

)ofB

anan

aD

uring

Stora

geat

34±

1◦ C

Tre

atm

ents

Stora

geper

iod

(day

)T1

T2

T3

T4

T5

T6

T7

T8

T9

LSD

(P<

0.05

)

pH 0

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

2.08

±0.

025j

0.04

325

5.05

±0.

020e

4.93

±0.

015f

5.43

±0.

010d

5.53

±0.

017c

4.86

±0.

006g

4.61

±0.

01h

5.70

±0.

02a

4.48

±0.

015i

5.59

±0.

012b

0.02

5110

5.17

±0.

006g

5.13

±0.

021h

6.13

±0.

026c

6.27

±0.

01b

5.31

±0.

006f

5.04

±0.

006i

5.91

±0.

006d

5.40

±0.

012e

6.31

±0.

015a

0.02

38TA

(%)

00.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

92±

0.01

3e0.

0220

51.

72±

0.18

7d1.

55±

0.15

4d3.

48±

0.10

8b3.

68±

0.13

8b1.

70±

0.10

9d1.

64±

0.12

9d3.

96±

0.19

8a2.

82±

0.23

4c4.

03±

0.10

3a0.

2705

104.

35±

0.11

8b4.

16±

0.13

4b2.

77±

0.08

5d2.

89±

0.07

7d3.

32±

0.10

8c3.

23±

0.11

0c2.

85±

0.09

6d4.

66±

0.14

7a2.

92±

0.11

3d0.

1926

Mea

ns

with

the

sam

ele

tter

sw

ithin

the

row

sar

enot

sign

ifica

ntly

diffe

rent

atP

<0.

05usi

ng

LSD

.Eac

hva

lue

isth

em

ean

for

thre

e(n

=3)

replic

ates

.The

valu

esre

pre

sente

d(a

–j)

inth

ere

sults

indic

ate

the

range

from

hig

her

tolo

wer

rank.

T1—

chito

san

(1%

);T2—

chito

san

(1.5

%);

T3—

calc

ium

chlo

ride

(1%

);T4—

calc

ium

chlo

ride

(1.5

%);

T5—

chito

san

(1%

)+

gibber

ellic

acid

(100

ppm

);T6—

chito

san

(1.5

%)

+gi

bber

ellic

acid

(100

ppm

);T7—

glyc

erol(9

8%);

T8—

jojo

ba

oil;

T9—

control(u

nco

ated

).

128


Sugars

Gradual increase was seen in the content of total sugars, reducing sugars,and non reducing sugars in coated and uncoated banana fruits, but theaccumulation of the sugars in coated fruits was found to be less (Fig. 1A,B, C). It is clear from the results that at the time of harvest the sugars werevery low, but with the passage of time, total sugars increased with ripening.An increase in reducing sugar might be attributed to enzymatic conversionof starch to reducing sugar and also to conversion of some non reducingsugar to reducing sugar through the process of inversion. The coatings ofchitosan, chitosan + GA3, and jojoba wax were found to lower the totalsugars, reducing sugars, and non reducing sugars compared to fruits of thecontrol set. Among all the coated fruits, the fruits of T8 (34.2 mg.g−1), T6(36.6 mg.g−1), and T5 (39.2 mg.g−1) sets showed significantly (P < 0.05)lower amounts of total sugar content compared to that of control fruits (52.8mg.g−1) (Fig. 1A, B, C). This view is supported by Hoa and Ducamp (2008)who studied the effects of different coatings on biochemical changes of ‘catHoa loc’ mangoes in storage and observed that the content of reducingsugars and total sugars were lower with respect to that of control fruits. Amaximum amount of reducing sugars (9.1 mg.g−1) in control fruits (Fig. 1B)might be due to rapid conversion of starch to sugars as a result of moistureloss and decrease in acidity by physiological changes during storage.

FIGURE 1 Effect of edible coatings on content of total sugars (A), reducing sugar (B), nonreducing sugar (C), and starch (D) of banana fruit during storage at 34 ± 1◦C. Vertical barsrepresent ±SE of means for three replicates. T1—chitosan (1%); T2—chitosan (1.5%); T3—calcium chloride (1%); T4—calcium chloride (1.5%); T5—chitosan (1%) + gibberellic acid(100 ppm); T6—chitosan (1.5%) + gibberellic acid (100 ppm); T7—glycerol (98%); T8—jojobaoil; T9—control (uncoated).


Starch

Starch is bulk polysaccharides in banana fruit and its degradation results inpronounced softening (Prasanna et al., 2007; Zhang et al., 2010). Significant(P < 0.05) variation was found in respect to starch content in the coatedbanana fruits during storage period (Fig. 1D). However, degradation ofstarch in coated fruit was slow as compared with control fruit and wasaccompanied by a delay in the increase of soluble sugar content. The resultof the present study further reveals that the amount of starch content wasvery high at the beginning of their storage period and thereafter startedto decline. A decrease in starch content during banana ripening was alsoobserved by Chacon et al. (1987). At the storage of 10 days interval, thefruits coated with T8 and T6 have shown the maximum amount of starchcontent, i.e., 146.6 mg.g−1 and 122 mg.g−1, respectively. Thus, the resultsof the present study indicate that the least value of starch content (i.e., 34.4mg.g−1 and 52.2 mg.g−1) was perceived in the T3 and T9 (control) treatedfruits, respectively (Fig. 1D), and these are in line with that obtained byIslam et al. (2001) who reported that the banana fruits coated with waxolhad a higher amount of starch compared to the control fruits.

Pigments

The data obtained pertaining to the total chlorophyl (chl.) and totalcarotenoids as affected by the coatings tested under the current study arepresented in Figures 2 and 3. The quantitative analysis of photosyntheticpigments indicates that they occur more in the coated fruits in both pulpand peel. In contrast, control fruits exhibit weaker stimulation on total chl.accumulation. All the treatments, except T7, showed significantly (P < 0.05)more amounts of total chl. in peel as compared to that of the control set(Fig. 2A). During the end of the storage period, the fruits coated with chi-tosan, chitosan + GA3, and jojoba coating have shown a higher impact onthe accumulation of photosynthetic pigments (chl. ‘a’, chl. ‘b’, and total chl.)in peel as well as pulp. The retardation of color development in the bananafruit coated with chitosan and chitosan + GA3 in this investigation can beattributed to the modified internal fruit atmosphere, which caused slowingdown of the ripening process indicating by lower change of peel color offruits. The coating reduced the fruit respiration and ethylene production(Eryani Raqeeb et al., 2009). The slow respiration and reduced ethylene syn-thesis, in turn, delayed ripening and senescence, resulting in less change inthe greenish yellow color of fruits (Kader et al., 1989). Higher amounts ofchl. ‘a’ (37.1 µg.g−1), chl. ‘b’ (12.9 µg.g−1), and total chl. (48.0 µg.g−1) inthe peel was seen in T6, T8, and T6, respectively, at the 10 days of storageperiod (Figs. 2A, B, C). In the case of pulp, the fruits treated with T6 treat-ment have revealed a greater amount of total chl., i.e., 6.0 µg.g−1 (Fig. 2D).


FIGURE 2 Effect of edible coatings on content of total chlorophylls (peel) (A), chlorophyll‘a’ (peel) (B), chlorophyll ‘b’ (peel) (C), and total chlorophylls (pulp) (D) of banana fruitduring storage at 34 ± 1◦C. Vertical bars represent ±SE of means for three replicates. T1—chitosan (1%); T2—chitosan (1.5%); T3—calcium chloride (1%); T4—calcium chloride (1.5%);T5—chitosan (1%) + gibberellic acid (100 ppm); T6—chitosan (1.5%) + gibberellic acid (100ppm); T7—glycerol (98%); T8—jojoba oil; T9—control (uncoated).

FIGURE 3 Effect of edible coatings on carotenoid content of banana peel during storage at34 ± 1◦C. Vertical bars represent ±SE of means for three replicates. T1—chitosan (1%); T2—chitosan (1.5%); T3—calcium chloride (1%); T4—calcium chloride (1.5%); T5—chitosan (1%)+ gibberellic acid (100 ppm); T6—chitosan (1.5%) + gibberellic acid (100 ppm); T7—glycerol(98%); T8—jojoba oil; T9—control (uncoated).

The control fruits have shown higher impact on their chlorophyll degrada-tion. The least amount of total chl. was seen in the uncoated fruits in peel aswell as pulp, i.e., 9.2 µg.g−1and 1.3 µg.g−1, respectively (Fig. 2A, D), com-pared to the fruits coated with chitosan, chitosan + GA3, and jojoba wax.The loss of green color was the most obvious change in bananas, whichwas probably due to the physicochemical changes by degradation of the


chlorophyll structure and increase in carotenoid pigments during storage.The principal agents responsible for this degradation might be the oxida-tive system, pH change, and enzymes, such as chlorophyllase (Willis et al.,1982b). The data of the present study suggested that the level of carotenoidcontent progressively increased in both the coated as well as uncoated fruitsduring their storage periods (Fig. 3). The increase in carotenoid content dur-ing storage might be due to a series of physicochemical changes, such asthe breakdown of chlorophyll and increase in carotenoid pigments of thepeel caused by the enzymatic oxidation and photo degradation. The delayin ripening and degradation of chlorophyll and retention of green color fora longer period also depend on the types of coating (Kittur et al., 2001).

Ascorbic Acid

Ascorbic acid is one of the most abundant antioxidants present in fruits.Ascorbic acid was found to maintain with postharvest application ofchitosan, chitosan + GA3, and jojoba coating. Chitosan treatment with GA3

(T6) had the highest content (26.2 mg.100 g−1) of ascorbic acid comparedwith other coatings and control (14.9 mg.100 g−1) fruits during 10 daysof their storage periods (Fig. 4). On the other hand, CaCl2-coated bananafruits have not shown any significant differences with control sets. Chitosancoating at 1 and 1.5% maintained the loss of ascorbic acid compared tothe uncoated ones. This study has demonstrated that the combined treat-ment (chitosan + GA3) delayed the increase of ascorbic acid and the lossat the ripening stage of the banana. After 10 days of storage, all the coat-ings, except CaCl2 and glycerol, were much more effective in reducing theascorbic acid loss of banana fruits than the uncoated (control) fruit. The

FIGURE 4 Effect of edible coatings on ascorbic acid content of banana fruit during storage at34 ± 1◦C. Vertical bars represent ±SE of means for three replicates. T1—chitosan (1%); T2—chitosan (1.5%); T3—calcium chloride (1%); T4—calcium chloride (1.5%); T5—chitosan (1%)+ gibberellic acid (100 ppm); T6—chitosan (1.5%) + gibberellic acid (100 ppm); T7—glycerol(98%); T8—jojoba oil; T9—control (uncoated).


present study showed that vitamin C content of chitosan and chitosan+GA3-coated bananas were highest among all the treatments at the end of thestorage. This may be due to the effect of chitosan coating on retardingripening and slowing down the metabolism activity, which causes oxidationof ascorbic acid. The reason for high vitamin C content in coated fruit canbe attributed to the slow ripening rate of chitosan-treated fruit. This viewis also shared by Abbasi et al. (2009), who reported that the ascorbic acidcontents in irradiated Crab chitosan-coated mango fruits were higher thanunirradiated chitosan-coated fruits at the end of the storage. Oxidation ofascorbic acid may be caused by several factors, including exposure to oxy-gen, metals, light, heat, and alkaline pH (Abbasi et al., 2009). As Ayranci andTunc (2003) stated, slowing down of vitamin loss was attributed to the lowoxygen permeability of the coating.

CONCLUSIONS

The results of the current investigation indicate that banana fruit coatedwith chitosan alone, chitosan in combination with gibberellic acid, andjojoba coatings cause a significant delay in the change of weight loss, decaypercentage, total soluble solids, pH, titrable acidity, sugar accumulation, pig-ment degradation, and ascorbic acid content compared to uncoated ones.Chitosan 1.5% and chitosan 1.5% + gibberellic acid 100 ppm was moreeffective as a protective coating on banana fruits by maintaining the qual-ity characteristics, prolonging the shelf life, and preserving the valuableattributes of banana fruits during the storage period. Hence, these coat-ings, being environmentally friendly, provide good handling procedures toenhance banana export to long distances with minimum losses.

ACKNOWLEDGMENT

Neeta B. Gol is grateful to the University Grant Commission (UGC), NewDelhi for financial support under the program of Meritorious Fellowship.

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