J Food Sci Technol 2009, 46(6), 604-605
SHORT COMMUNICATION
Optimization of storage temperature for maintaining quality of guava Mahajan BVC*, Sharma SR, Dhall RK Punjab Horticultural Post-harvest Technology Centre, Punjab Agricultural University, Ludhiana-141 004, India *Email:
[email protected] Guava (Psidium guajava L.) fruits of cultivar ‘Allahabad Safeda’ were harvested at green mature stage, packed in perforated polythene bags and stored at 0±1°C, 3±1°C, 6±1°C, 9±1°C and 90-95% RH. Fruits stored below 60C developed chilling injury symptoms like, surface pitting, brown streaks, abnormal ripening and bland taste after 7 days of storage, while fruits at 9°C developed faster ripening, pleasant flavour and over softening on further storage. The optimum temperature for storage of guava fruits was 6°C and 90-95% RH for maintaining highly acceptable sensory quality. At this temperature the fruits had attractive colour, pleasant flavour and acceptable quality and can be stored up to 2-3 weeks with post-storage shelf-life of 3 days at 20-21°C and 65-70% RH. Keywords: Guava, Storage, Temperature, Quality, Chilling injury
Guava fruit is known for its pleasant flavour, refreshing taste and nutritional value. It is successfully grown all over India and contributes 0.4% of total fruit production with estimated production of 1.75 million tons from 0.25 million hectares (Singh 2007). There is tremendous demand of fruit for fresh and processing purpose in both domestic and international markets. The share of guava in fresh fruit export from India is merely 0.65% which can be further boosted, if fruit is properly handled after harvest. Guava is a climacteric fruit (Akamine and Goo 1979), ripens rapidly after harvest and has short-shelf life (Pantastico et al 1975). Therefore, guava cannot be sent to distant markets under normal conditions. Storage of fruits at low temperatures for a definite period is a common practice in developed countries such as North America and Northern Europe (Cambell 1994). Low temperature may delay or retard ripening and may reduce spoilage. But the problem with guava fruit is its high chilling sensitivity (Wang 1989). Relatively little is known with respect to the sensitivity and the response of guava fruit to chilling temperatures. The effect of low temperature (0-3°C) on storage life of guava fruits had been examined and a storage life of 2-3 weeks has been reported (Selvan and Bal 2005). Such low temperature storage causes fruit to lose consumer appeal and economic value. In the present investigation an attempt was made to optimize the storage temperature for guava fruit and storage behaviour of guava fruit has been studied at the
optimum temperature. The guava (Psidium guajava L.) fruits of cv. ‘Allahabad Safeda’ of uniform size and free from blemishes and injuries were harvested at colour break stage. The fruits were surface sanitized with water containing 100 ppm chlorine, air dried, packed in CFB boxes and stored at 0±1°C, 3±1°C, 6±1°C, 9±1°C and 90-95% RH. The observations on the development of chilling injury and changes in physico-chemical constituents were recorded at 7 days intervals. The physiological loss in weight (PLW) of the fruit during storage was estimated on initial weight basis and expressed in percentage. The firmness of the fruit was measured with the help of penetrometer (Model FT-327, USA) using 8 mm stainless steel probe and expressed in kg force. The colour of the fruit was recorded with Colour Difference Meter (Mini Scan XE Plus, Hunter Lab, USA) and expressed as L, a, b Hunter colour values (Hunter 1975). The total soluble solids (TSS) content was recorded with hand refractometer (Erma, Japan) and correction at 20°C was applied. The acidity, sugars and ascorbic acid contents were determined as per AOAC (1990). The sensory quality of the fruit was determined by a panel of 10 judges as per Hedonic scale using 1-9 points (Amerine et al 1965). The experiment was laid out in completely randomized design with 3 replications and each replication comprised of 5 kg fruits. The studies were conducted continuously for 2 years. Results are presented in Table 1. Fruits stored below 6°C and 90-95% RH 604
developed chilling injury-like-symptoms such as surface pitting, brown streaks formation on the peel and off-flavour of pulp after 7 days of storage. During post storage period, the fruits became shriveled, soft and of discoloured appearance after 24 h exposure to ambient conditions. On the other hand, the fruits stored at 9°C developed faster ripening and softening during storage. These fruits developed pleasant flavour and registered short storage life of 7 days. However, the fruits stored at 6°C and 9095% RH were fresh in appearance and developed uniform-light yellow colour and are having pleasant flavour. The optimum storage temperature with respect to maintenance of quality for guava fruits was found to be 6±1°C and 90-95% RH. The PLW increased during storage and ranged between 0.96 and 5.2% during storage period of 28 days. The fruits were firm and fresh up to 21 days of storage with 4.8% moisture loss, but thereafter fruits started becoming soft, shriveled and foamy with further rise in moisture loss. It has been pointed out that losses of less than 5% in weight do not detract materially and are of little economic significance in majority of horticultural crops. However, the water loss above 5% is generally considered to cause a noticeable loss of quality and value (Kays 1991). The firmness of fruit followed a declining trend during storage (8.6 to 2.5 kg force). The decline in firmness was gradual initially up to 2 weeks, when fruits registered firmness of 5.1 kg force after 2 weeks of storage, but later on, the decline was sharp and the puncture force
J Food Sci Technol 2009, 46(6), 604-605 Table 1. Physico-chemical and sensory quality changes in guava fruits during conditions Storage, PLW, Firmness, Hunter colour Sensory TSS TS days % kg force L a b quality % % Cold storage at 6±1°C, 90-95% RH 0 8.6 51.0 -8.5 21.5 4.0 9.0 5.0 7 0.9 6.9 64.6 -5.8 30.0 7.6 10.0 5.7 14 2.3 5.1 66.0 3.7 31.5 8.0 11.0 6.2 21 4.8 3.5 66.5 9.1 25.7 7.2 8.4 5.2 28 5.1 2.5 64.5 6.1 20.0 3.1 7.1 4.8 CD at 5% 0.3 0.2 0.2 0.2 0.4 0.3 0.2 0.2 Post cold storage at 20-21°C, 60-65% RH for 3 days 14 4.3 2.7 54.5 2.3 29.7 7.3 10 5.8 21 5.4 1.8 50.2 2.1 22.8 7.0 8 4.7 28 7.5 0.7 40.2 1.1 18.5 3.0 8 4.5 CD at 5% 0.5 0.7 0.2 0.1 0.3 0.2 0.4 0.1
different storage Acidity AA % mg/100g
References 0.48 0.36 0.24 0.23 0.20 0.03
150 126 123 115 106 0.9
0.18 0.17 0.15 0.04
112 105 102 2.1
PLW: Physiological loss in weight, TSS: Total soluble solids; TS: Total sugars, AA: Ascorbic acid, (n=3)
of 3.5 and 2.5 kg was recorded after 21 and 28 days of storage, respectively. Fruit firmness is one of the most crucial factors in determining the keeping quality of fruits during market handling (Shear 1975). Softening of fruits during storage is caused by either breakdown of insoluble protopectin into soluble pectin or by cellular disintegration leading to increased membrane permeability (Mootoo 1991). There was significant improvement in yellowness (b) value of fruit up to 2 weeks of storage. The fruits were greenish yellow at the time of harvest and attained uniform yellow colour after 2 weeks of storage. Thereafter, sudden fall in ‘b’ value was noticed. Although colour of guava was changing at a rate that could be easily measured instrumentally, but sensory panel score for colour remained in acceptable range during 3 weeks storage. However, after 28 days of storage, the fruits were dull and yellowish brown in colour indicating over ripening or senescence. A gradual increase in Hunter values (L, a, b) were also observed in mango during ripening and storage (Kudachikar et al 2001). The sensory quality of guava improved up to 2 weeks of storage and recorded score of 8.0, thereafter a gradual decline in sensory quality was noticed on third week of storage. However, on 4th week of storage a sharp decline in sensory quality was observed. The improvement in sensory quality is obvious due to build up of sugars
content and Hunter colour values declined, but overall the fruits maintained the sensory acceptability for 3 days at 2021°C after 14 and 21 days of cold storage.
and acids as a result of hydrolysis of starch and other complex chemical changes leading to development of flavour. The TSS and total sugars which were fairly low at harvest (9° Brix and 5.0%, respectively), increased during storage and reached a peak value (11.0° Brix, 6.2%) at 15 days of storage and declined thereafter. The increase in TSS and sugars up to 15 days of storage may be due to hydrolysis of starch into sugars and conversion of organic acids. On completion of hydrolysis of starch, further increase in TSS/sugars did not occur. Hence, decline in these attributes is predictable (Smith et al 1979) as these are the primary substrates for respiration. A declining trend from 0.48 to 0.20% in the titratable acidity during storage was noticed which could be attributed to the use of organic acids as respiratory substrate (Rhodes et al 1968). Ascorbic acid content of 150 mg/100 g fresh weight was maximum at harvest, which reduced to 106 mg/100 g at the end of storage period. This fall in ascorbic acid during storage might be due to its oxidation (Lin et al 1988). Guava fruits were taken out from cold storage after 14, 21 and 28 days and kept at 20-21°C and 65-70% RH for 3 days to simulate changes during supermarket retail conditions. During poststorage at ambient condition, the PLW and firmness breakdown of fruit increased while TSS, sugars, acidity, ascorbic acid
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Received 17 November 2008; revised 11 May 2009; accepted 12 May 2009
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