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

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1 Journal of Scientific & Industrial Research Vol. 59, November 2000, pp 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 Techno logy, University of H ortic ulture & Forestry, Solan , 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 per cent EM C. The quality of dri ed fruit deteriorated significantl y in polyethylene and glass jars 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 distribution 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 vital 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 fruits 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 acidity, preventing the loss of natural fl avour alongwith better retention of nutrients 4. 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 and analysed for various physico-chemical characteristics like average fruit weight ( ± 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 ( ± 0.06 B), titratable acidity ( 1.06 ± 0.02 per cent), total

2 950 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 fruits 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 fruits were taken out from the osmotic solution, drained, washed in tap water to remove adhering syrup and spreads on tissue paper to remove excess surface water. Dehydration - The osmoticall y 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. Moisture 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 acid and ascorbic acid content by titration method using standard 2,6-dichlorophenol indophenol dye soluti on 5. Sugars (reducing and total) were estimated by Lane and Eynon's 6 volumetric method. Total carotenoids content was determined by petroleum ether extract of sample, measuring its intensity with spectrophotometer (S pectronic-20) at 460 nm as per method described by Ranganna 7. Non-enzymatic browning was determined by measuring the absorbence of a sample extract with 60 per cent aqueous ethyl alcohol at 440 nm using spectrophotometer 7. Sulphur-dioxide was estimated by titramatic method as described by Ranganna 7, using 0.02 N iodine solution to a blue end point with starch as an indicator. Moisture Sorption Behaviour - Moisture sorption behaviour of dried fruits was determined by weight equilibrium method using H 2 S0 4 of different normalities with relative humidities ranging between 0 to 100 per cent, as described by Ranganna 7. The equilibrium moisture content at which the product showed dark colouration with softening was identified as the critical point. Sensory Evaluation - The sensory evaluati on of dried fruits was carried out for colour, fl avour, texture and overall acceptability by a panel of 7 semi trained judges using a nine-point Hedonic scale 8. Microorganisms - Slides were prepared from the growth of the microbs on the fru its kept at high relative humidity during moisture sorption study and were identified on the basis of their structure. Statistical Analysis - The data for different physico-chemical attributes were analysed by using Completely Randomized 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 their permeability to air and vapours as reported by Sharma et al. 10 for apple slices. Reduction in total soluble solids du ring storage was observed in all packages but statisticall 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 browning process during storage. The reducing sugars increased and total sugars decreased in all packages during this study, it was maximum in polyethylene and minimum in lami nated pouches. The increase in reduci ng sugars i

3 SHARMA et al.: QUALITY & SHELF-LIFE OF OSMO-AIR DRIED APRICOT 951 Parameter Table I -Chemical composition of osmo-air dried apricot in different packages during storage Storage (months) Packaging p CDo.os s PxS Moisture TSS ("B) Titratable acidity Reducing sugars Total sugars Ascorbic acid (mg/100 g) Carotenoids (mg/1 00 g) NEB (OD at 440 nm) PEl ' I S0 2 (ppm) = Polyethylene pouches, =Glass jars, =Laminated pouches, P=Package, S=Storage NS NS NS 0.88 NS 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

4 952 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 thermolabile 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 S0 2 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 slices. 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 initially 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 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 (aw = 0.48) at 25 C. At hi gher levels of relative humidity the dried products have a tendancy to absorb moi sture, depending upon their water activity and with thi s additional moisture pick-up dried fruits turn dark brown. This may be attributed to oxidation of ascorbic acid to dehydro ascorbic acid and oxidati on of tannins to gallic acid and increased browning due to NEB reactions. During this study, the dried apri cot samples at and abvoe 80 per cent relative humidity became succeptible to moulds. The moulds identified were Aspergillus and Penicillium. The sensory quality deteriorated significantl 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?quilib ri um moisture content Equil ibrium Days to reach Remarks humidity equilibriu m Change in co lour, harder texture Little change in colour, slightl y harder textu re No change in colour and texture do- -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 ( per cent EMC), Danger point (D)= 55 per cent RH (I I.26 per cent EM C)

5 SHARMA et a/.: QUALITY & SHELF-LIFE OF OSMO-AIR DRIED APRICOT 953 Attribute Table 3 - Packaging Sensory attributes of osmo-air dried apri cot in different packages during storage Storage (months) CDo.os p s PxS Colour Flavour/taste Texture NS Overall acceptability = Polyethylene pouches, =Glass jars, =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. References F A 0, Production Year Book, Food and Agriculture Organization, Rome, 1998, Lal B B, Joshi V K & Sharma R, Physico-chemical and Sensory Evalu ation of Sauce and Chutney Prepared from Wild Apricot (chulli), Indian Food Pack, 43(4) ( 1989) pp Bhutani V P & Sharma Y P, Studies on Drying of Apricot Grown Under Dry Temperate Conditions, Indian Food Pack, 42(4) (1988) pp Pa nting 1 D, Walters G. Forrey R R & Stanley W L, Osmotic Dehydration of Fruits, Food Techno/, 20(1 0) (1966) pp AO A C, Official Methods of Analysis, Association of Official Analytical Chemists, Washington DC. USA, 1975.

6 954 J SCI IND RES VOL 59 NOVEMBER Lane J H & Eynon L, Determinati on of Reducing Sugars by Fehling's Solution with Methylene Blue As An Indicator, J Soc Chern lnd, 42 (1923) 32T. 7 Ranganna S, Handbook of Analysis and Quality Control for Fruits and Vegetable Products (Tata McGraw Hill Publishing Co, Ltd, New Delhi) Amerine M A, Pangborn R M & Roessler E B, Principles of Sensory Evaluation of Foods (Academic Press, New York) Mahony M 0, Sensory Evaluation of Food : Statistical Methods and Procedures (Marcel Dekker Inc, New York) I 0 Sharma K D, Sethi V & Maini S B, Effect of Pretreatment and Package on Chemical and Sensory Characteri sti cs o f Dried Apple, Indian Food Pack (In press). II C legg J S & Morton A D, Carbonyl Compounds and the Non-enzymatic Browning of Lemon Juice, J Sci Food Agric, 16 (1965) pp Ambrose D C P & Sreenarayanan V V, Studies on Dehydration of Garlic, J Food Sci Tee/mol, 35(3) ( 1998) pp Mir M A & Nath N, Storage Changes in Fortified Mango Bars, J Food Sci Techno{, 30 ( 1993) pp Sagar V R & Khurdiya D S, Studies on Dehydration of Dashehari Mango Slices, Indian Food Pack, 53(1) ( 1999) pp Sharma K D, Sethi V & Maini S B, Changes in Quality of Osmo-vac Dried Apple Slices on Storage, J Sci lnd Res, 57(7) ( 1998) pp