Journal of Scientific & Industrial Research

Vol. 59, November 2000, pp 949-954

Effect of Packaging on Quality and Shelf-life of Osmo-air Dried Apricot

K D Sharma, Rajesh Kumar and B B Lal Kaushal

Department of Postharvest T echno logy, University of H ortic ulture & Forestry, Solan 173 230, India

Received : 23 M arch 2000; accepted : 12 July 2000

Osmoticall y dehydrated apricot with a good consumer acceptability were developed and evaluated for their quality in different packages during storage at 13-28"C. The critical point for the storage of osmo-air dehydrated apricot was at 60 per cent relative humidity with 12.5 per cent equilibrium moisture content (EMC) whereas the optimum equilibrium relati ve humidity (ERH) was found to be 48 per cent at 8.5 1 per cent EM C. The quality of dri ed fruit deteriorated significantl y in polyethylene and glass j ars during storage study of 6 months however, a minimum change in chemical composition and sensory attributes was observed in laminated pouches. At the same time laminated pouches were attractive and convenient to handle which is beneficial for distribut ion and from marketing point of view.

Introduction

Apricot (Prunus armeniaca L.) is an important stone fruit grown in the temperate regions of the world. The world production of apricot is estimated to be 24, II ,000 metric tonnes, toward which India contributes about 7,000 metric tonnes 1

• In India, Jammu and Kashmir, Himachal Pradesh, and hills of Uttar Pradesh are the major apricot producing areas, occupying a significant place in the horticultural produce of these states and plays a vita l role in the economy of the local people. However, due to highly perishable nature, apricot can not be stored beyond 4-5 d at room temperature and 2 to 4 weeks at low temperature. Fruits are utilized for the preparation of chutney, jam, and squash on a limited scale though, they could' be canned, frozen, dried, and made into JUice, sauce and confectionar/. Dried apricot constitutes an important item among the dried fruits consumed in India. Excellent quality fru its for drying are extensively grown in Kinnaur di strict of Himachal Pradesh and Ladakh region of Jammu and Kashmir. However, only a small quantities are dried in open sun by the local people which are unhygienic , contaminated, discoloured and inferior in taste'. At the same time, the dried fruit s are packed and marketed in polyethylene pouches resulting in fast deterioration in colour, texture and overall acceptability and hence, poor returns to the growers and the people associated in thi s industry. On the

other hand, apricot varieties commercially grown in mid hills of Himachal Pradesh are not suitable for drying, due to low sugars and high acids content persent in fruits. Thus, there is a need to develop a technique to produce good quality dried fruits to meet the consumers demand as well as to utilize low quality surplus fruits in these area to provide employment and better return to the local farmers .

Osmotic dehydration of fruits in hypertonic solution enhance the quality of dried fruits to a great extent by increasing the sugar content, reducing ac idity, preventing the loss of natural fl avour alongwith better retention of nutrients4

. Therefore, the present investigation was undertaken to develop the method for osmo-air dehydration of apricot and evaluating their quality retention in different packages during storage.

Materials and Methods

Raw Material - The fruits of apricot cultivar 'Farmingdale' harvested at optimum maturity were obtained from orchard of University of Horticulture and Forestry, Solan (HP) during the year 1998-99 and ana lysed for various physico-chemical characteristics like average fruit weight ( 15 .80 ± 1.10 g), specific gravity ( 1.03 ± 0.02 glee) , firnmess (I 0.85 ± 1.22 lbs/inch\ pulp-stone ratio (8 .22 ± 0.86), moisture (82.40 ± 1.55 per cent), total soluble solids ( 11.85 ± 0.06°B), titratable acidity ( 1.06 ± 0.02 per cent), total

950 1 SCIIND RES VOL 59 NOVEMBER 2000

sugar (9.20 ± 0.33 per cent), ascorbic acid (8.33 ± 0.07 mg/lOOg) and total carotenoids (670 ± 8 ug/lOOg). Other materials like sugar, glass jars, polyethylene pouches ( 150 gauge), laminated pouches (220 gauge) etc. were purchased from local market.

Treatment - The fruit s were washed and lye­peeled (1.0 per cent boiling NaOH solution) for 30 sec followed by washing in running water. A 70°B sugar (sucrose) syrup containing 0.05 per cent potassium meta-bisulphite, at 50°C was used as osmotic solution for immersing the pre-treated fruits in I :3 ratio for 6 h without any agitation . After 6 h osmotic dip, the fruit s were taken out from the osmotic solution, drained, washed in tap water to remove adhering syrup and spreads on ti ssue paper to remove excess surface water.

Dehydration - The osmotically treated fruits were further dehydrated in a cabinet drier, on a aluminium tray (76 x 56 em) with 3 kg tray load at ± 2 °C to a constant moisture content ranging from 8 to I 0 per cent, packed in polyethylene pouches, glass jars and laminated pouches and stored between 13 to 28 °C for studying shelf-life and changes in quality during storage. The product was analysed at 2, 4 and 6 months storage intervals.

Analysis- Standard analytical procedures were followed for determination of different qu ality parameters during storage. Moi sture content was determined by drying the samples to a constant weight in a hot air oven at 70°C for 16 h and total soluble solids by hand refractometer after mak ing solution sample from dry fruit with 15 times dilution. Titratable acidity was estimated as per cent malic ac id and ascorbic ac id content by titration method using standard 2,6-dichlorophenol indophenol dye soluti on5

.

Sugars (reducing and total ) were esti mated by Lane and Eynon's6 volumetric method . Total carotenoids content was determined by petroleum ether extract of sample, measuring its intensity with spectrophoto­meter (Spectronic-20) at 460 nm as per method described by Ranganna7

. Non-enzymatic browning was determined by measuring the absorbence of a sample extrac t with 60 per cent aqueous ethyl alcohol at 440 nm using spectrophotometer7

. Sulphur-dioxide was estimated by titramatic method as described by Ranganna7

, using 0.02 N iodine solution to a blue end point with starch as an indicator.

Moisture Sorption Behaviour - Moisture sorp­tion behaviour of dried fruit s was determined by weight equilibrium method using H2S04 of different normalities with relative humidities ranging between 0 to 100 per cent, as described by Ranganna7

. The equilibrium moi sture content at which the product showed dark colouration with softening was identified as the critical point.

Sensory Evaluation - The sensory evaluati on of dried fruit s was carried out for colour, fl avour, tex ture and overall acceptability by a panel of 7 semi ­trained judges using a nine-point Hedonic scale8

.

Microorganisms - Slides were prepared from the growth of the microbs on the fru its kept at high relative humidity during moi sture sorption study and were identified on the bas is of their structure.

Statistical Analysis - The data for different physico-chemical attributes were analysed by using Complete ly Randomi zed Design (CRD) and data for sensory evaluation were analysed by Randomized Block Design (RBD), as described by Mahon/. All the experiments were replicated thrice and values compared at 5 per cent level of significance.

Results and Discussion

The data for chemical quality parameters during storage (Table I) indicated that the polyethylene packed dried apricot gained more moisture as compared to other packages. No gain/loss in moisture was noticed in laminated pouches during storage peri od of 6 months. The increase in moi sture content in polyethylene packed samples mi ght be due to the ir permeability to a ir and vapours as reported by Sharma et al. 10 for apple s lices. Reduction in total soluble solids du ring storage was observed in all packages but stati st ica ll y there was no significant difference. However, max imum reduction occurred in polyethylene packed dried apricots. A slight decrease in ac idity in all packages was noticed during storage but, polyethylene pouches packed sample exhibited more decrease. The decrease may be due to the utilization of ac ids in hydrolys is of non-reducing sugars and in non-enzymatic brown ing process during storage. The reducing sugars increased and total sugars decreased in all packages du ring this study, it was maximum in polyethylene and minimum in lami nated pouches. The increase in reduci ng sugars i

SHARMA et al.: QUALITY & SHELF-LIFE OF OSMO-AIR DRIED APRICOT 951

Table I -Chemical composition of osmo-air dried apricot in different packages during storage

Parameter Packaging Storage (months) CDo.os

Moisture (per cent)

TSS ("B)

Titratable acidity (per cent)

Reducing sugars (per cent)

Total sugars

(per cent)

Ascorbic acid (mg/100 g)

Carotenoids (mg/1 00 g)

NEB (OD at 440 nm)

S02 (ppm)

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEP

GJ

LP

Mean

PEl '

GJ

LP

Mean

PEP

GJ

0

8.51

8.51

8.51

8.51

82.24

82.24

82.24

82.24

3.21

3.21

3.21

3.21

43.75

43.75

43.75

43.75

77.55

77.55

77.55

77.55

16.42

16.42

16.42

16.42

1.68

1.68

1.68

1.68

0.010

0.010

0.010

0.010

367.0

367.0

2

10.26

9.05

8.51

9.27

80.22

80.65

81.80

80.89

3.16

3.18

3.19

3.17

44.56

44.50

44.06

44.37

76.90

77.12

77.20

77.07

13.83

14.37

14.75

14.32

1.50

1.53

1.59

1.54

0.065

0.050

0.010

0.042

331.4

336.5

4

11.52

9.86

8.51

9.96

78.04

78.50

81.08

79.21

3.11

3.13

3.17

3.13

45.39

45 .28

44.35

45.00

76.23

76.58

76.77

76.53

11.36

12.39

12.67

12.14

1.35

1.41

1.47

1.41

0.111

0.105

0.014

0.076

298.9

306.7

6

12.78

I0.52

8.51

10.60

77.61

77.83

80.85

78.66

3.07

3.09

3.13

3.10

46.22

45 .94

44.65

45 .60

75.65

75 .92

76.38

75.98

8.84

10.43

11 .57

10.28

1.14

1.23

1.35 1.24

0.250

0.2 15

0.020

0.162

265.4

284.6

Mean

10.77

9.48

8.51

9.58

79.45

79.80

81.49

80.25

3. 14

3.15

3.17

3.15

44.98

44.87

44.20

44.68

76.58

76.79

76.97

76.78

12.61

13.4 1

13 .86

13 .29

1.41

1.44

1.50

1.45

0. 109

0.095

0.013

0.072

315.7

323.7

p

0.041

NS

0.017

0.76

0.031

0. 12

0.018

0.003

1.15

s PxS

0.047 0.082

NS 1.53

0.020 NS

0.88 NS

0.036 0.063

0. 15 0.25

0.021 0.039

0.004 0.006

1.17 2.30

LP 367.0 358.9 349.8 342.7 354.6 Mean 367.0 342.2 318.5 297.5 331 .3

PEP= Polyethylene pouches, GJ=Glass jars, LP=Laminated pouches, P=Package, S=Storage

due to the hydrolysis of non-reducing sugars to reducing sugars while decrease in total sugars during storage might be due to utilizatio!l of sugars in non­enzymatic browning.

Considerable reduction of ascorbic acid was observed during 6 months storage of with a maximum

in the polyethylene and least in samples packed in laminated pouches . Loss of ascorbic acid was due to its oxidation 11 and more loss in polyethylene packed samples might have been due to more availability of oxygen during storage. Similar results were also noticed by Ambrose and Sreenarayanan 12 in stored garlic powder. Laminated pouches packed samples

952 J SCI IND RES VOL 59 NOVEMBER 2000

showed minimum degradation of carotenoids to that of other two packages during storage. The degradation could be due to thermol abile and photosensitive nature and oxidation of carotenoids during storage 13

. After 6 months of storage, maximum (0.250) non-enzymatic browning was observed in polyethylene packed samples as a result of higher oxidation which is affected by different fac tors like acids, sugars, oxygen, and water acti vity during storage. Better retention of S02 was found in laminated pouches . It might be due to impermeability of laminated pouches to air, vapour and gases. Similar results have been reported by Sagar and Khurdiya 14 in dehydrated mango s lices.

ERH data of dried apricot presented in Table 2 which revealed that the moisture pick up by the samples held at different relative humidities caused the deterioration of the product. The dried fruit s with initia lly attractive colour and crisp texture turned

,, dark, soft and mouldy with the increase in relati ve humidity. The critical point during storage of osmo­air dehydrated apricot was at 60 per cent re lative humidity with 12.5 per cent equilibrium moisture content (EMC) whereas, the optimum equilibrium re lati ve humidity (ERH) was found to be 48 per cent (aw = 0.48) at 25°C. At higher levels of relative humidity the dried products have a tendancy to absorb moi sture, depending upon their water activity and with thi s additi onal moisture pick-up dried fruits turn dark brown. Thi s may be attributed to oxidation of ascorbic acid to dehydro ascorbic acid and ox idation of tannins to gallic ac id and increased browning due to NEB reactions. During this study, the dried apricot samples at and abvoe 80 per cent re lative humidity became succeptible to moulds. The moulds identified were Aspergillus and Penicillium.

The sensory quality deteriorated s ignificantl y in all packagings during 6 months of storage (Table 3) .

Table 2- Equilibrium relati ve humidity (ERH ) of dehydrated apricot at 25"C

J?quilibrium Equil ibrium

moisture content humidity

(per cent) (per cent)

7. 10 0

7.32 10

7.54 20

7.49 30

8. 14 40

9.41 50

12.50 60

14.75 70

21.71 80

29.76 90

32.38 100

Days to reach

equilibriu m

24

23

20

19

18

18

16

16

17

Remarks

Change in co lour, harder texture

Little change in colour, slightl y harder textu re

-do-

No change in colour and texture

-do-

-do-

Soft textu re, no change in colour

Soft texture, colour light brown

Very soft and dark in colour, mould growth appeared after 19 d

Very soft and mould growth appeared after 13 d

Very soft and mould growth appeared after I I J

Initial poi nt (I)= 48 per cent RH (8.5 per cent EMC), Critical point (C) = 60 per cent RH ( 12.50 per cent EMC), Danger point (D)= 55 per

cent RH ( I I .26 per cent EM C)

SHARMA et a/.: QUALITY & SHELF-LIFE OF OSMO-AIR DRIED APRICOT 953

Table 3 - Sensory attributes of osmo-air dried apri cot in different packages during storage

Storage (months) CDo.os Attribute Packaging

0 2 4 6 Mean p s PxS

Colour PEP 8.23 7.74 7.25 6.75 7.49 0.0 16 0.01 8 0.031

GJ 8.23 7.78 7.34 6.90 7.56

LP 8.23 7.90 7.58 7.25 7.74

Mean 8.23 7.8 1 7.39 6.96 7.59

Flavour/taste PEP 8. 15 7.30 6.44 5.55 6.86 0.011 0.013 0.023

GJ 8.15 7.37 6.5 1 5.76 6.94

LP 8. 15 7.70 7.25 6.80 7.47

Mean 8. 15 7.46 6.73 6.04 7.09

Texture PEP 7.70 7. 18 6.65 6. 18 6.92 0.89 1.03 NS

GJ 7.70 7.28 6.86 6.45 7.07

LP 7.70 7. 35 6.98 6.68 7. 17

Mean 7.70 7.27 6.83 6.44 7.06

Overall PEP 8. 15 7.60 7.02 6.50 7.3 1 0.036 0.042 0.072

. acceptability GJ 8.15 7.68 7.10 6.72 7.41

LP 8. 15 7.76 7.45 7.15 7.62

Mean 8. 15 7.68 7.19 6.79 7.45

PEP= Polyethylene pouches, GJ=Gl ass j ars, LP=Laminated pouches, P=Package, S=Storage

The maximum deterioration of sensory quality noticed in polyethylene packed dried apricot, while samples stored in laminated pouches showed least changes. Sharma et al. 15 have also reported reduction in sensory scores of dried apple slices during storage. However, there was hardly any spoilage or degradation in any sample in the study. Reduction in sensory quality during storage may be attributed to reduction of so2 and increase in moisture in samples resulting in the non-enzymatic browning, oxidation and changes in other chemical constituents of product. Keeping in view the changes during storage of 6 months, it was concluded that the packaging of dehydra1ed apricot in hermatically sealed laminated pouches preserved the carotenoids and ascorbic acid with a little or no changes in chemical and sensory attributes of the product. The product can successfully

be stored in these pouches beyond 6 months also, since, the quality was as good as to that of a fresh dried fruits.

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954 J SCI IND RES VOL 59 NOVEMBER 2000

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