Effect of shrink wrap packaging for maintaining quality of cucumber during storage

Immature green cucumber cv. ‘Padmini’ fruits were individually shrink wrapped with Cryovac D955 (60 guage) film and stored at 12 ± 1 °C, 90–95% RH as well as ambient conditions (29–33 °C, 65–70% RH). At 12 ± 1 °C and 90–95% RH, individual shrink wrapped cucumber recorded minimum Physiological loss in weight (0.66%) as compared with unwrapped fruits (11.11%) at the end of refrigerated storage (15 days). The softening (loss of firmness) was maximum (1304.6–876.6 g force) in unwrapped cucumbers whereas in shrink wrapping, minimum loss in firmness (1304.6–1065.3 g force) was observed after 12 days storage at 12 ± 1 °C and 90–95% RH but greater loss of weight and firmness makes the control cucumbers unmarketable after 9 days of storage. There were no rotting at all both in shrink wrapped and unwrapped cucumbers upto 15 days of storage at 12 ± 1 °C and 90–95% RH. After 15 days storage of shrink wrapped cucumbers at 12 ± 1 °C and 90–95% RH, there was loss of green colour and development of yellowness and decay. The sensory attributes score was highest in shrink wrapped cucumbers as compared to unwrapped cucumbers at end of both storage conditions. Thus it can be concluded that individual shrink wrapped cucumber can be stored well upto 15 days at 12 ± 1 °C and 90–95% RH and for 5 days at ambient conditions (29–33 °C, 65–70% RH) with maximum retention of green colour, no spoilage, minimum weight and firmness loss and very good sensory quality attributes whereas, unwrapped fruits can be stored well upto 9 days at 12 ± 1 °C and 90–95% RH and for 2 days at ambient conditions with maximum retention of physico-chemical quality attributes.

Cucumber (Cucumis sativus L.) is an important vegetable in the world but due to highly perishable nature, it is not suited for long term storage even at low temperature. The main deteriorative changes in cucumber during storage and distribution are mostly due to yellowing, loss of moisture leading to shriveling and physiological injury caused by low temperature (Adamicki 1985 ). Therefore the firmness, colour and size are important quality characters which affect the market price of cucumber. Additional quality indices are freedom from handling defects and decay. Cucumbers are susceptible to chilling injury at 10 °C or low temperature and yellowing at 15 °C or higher, therefore cucumbers must be stored at temperatures between 10 °C and 15 °C. Yellowing during the postharvest period in also observed if the fruits were harvested at an advanced stage of development or exposure to ethylene during storage. Further, they are very susceptible to shriveling and hence the humidity during storage, transport and marketing should be kept at 90–95%. Waxing is generally used to reduce moisture loss from cucumber but it increases the incidence of decay (Seagall et al. 1974 ). Researchers have studied the effect of shrink wrapping on storage life and quality of many fruits and vegetables (Ben-Yehoshua 1985 ; Heaton et al. 1990 ; Sonkar and Ladaniya 1999 ; Sudhakar Rao and Gopalakrishna Rao 2002 ; Singh and Sudhakar Rao 2005 ). Individual shrink wrapping (ISW), a form of modified atmosphere packaging is used to enhance the storage life and to maintain the harvest freshness of fruits and vegetables. The principal advantage of shrink wrapping are: reduced weight loss, minimized fruit deformation, reduced chilling injury and reduced decay by preventing secondary infection. Sudhakar Rao et al. ( 2000 ) studied the effect of MAP and shrink wrapping on shelf life of cucumber and reported that shrink wrapping with Polyethylene (PE) film can extend the shelf life of cucumber upto 24 days at 10 °C. Hence in the present studies were attempted to see the feasibility of shrink wrapping of cucumber for extension of storage life and maintaining quality at ambient as well as low temperature storage conditions.

Materials and methods

Immature green cucumber cv. ‘Padmini’ (Seminis Seeds Pvt Ltd) was harvested in 2nd week of June from the field of progressive farmer of district Ludhiana (Punjab). Misshapen, damaged, decayed and defective were sorted out and healthy uniform size green cucumbers were selected for the present studies. Ten cucumbers were randomly selected from the lot of experimental and their physical attributes were studied before shrink wrapping. The fruits were shrink wrapped with Cryovac D955 (60 guage) film procured from Cryovac Division, W.R. Grace and Co., Duncan, SC. The Cryovac D955 film is a biaxially oriented high density polyethylene (O2 and H2O transmission rates; 8900 cm2/m2/24 h and 1.48 g/100 in./h respectively). Shrink wrapping was achieved by sealing individual cucumber in loose pouches of shrink wrap film and then passing through shrink wrapping machine (Model BS-450 shrink packing machine, Samrath Engineers, India) at 165 °C for 5–7 s. The storage of wrapped and unwrapped fruits were carried out in walk in cold room maintained at 12 ± 1 °C and 90–95% RH whereas another lot was kept under ambient conditions (29–33 °C, 65–70% RH) of the laboratory.

The experimental data on physiological loss in weight (PLW), colour, firmness, sensory quality and decay were recorded at 1 and 2 days interval of storage at ambient and cold storage conditions, respectively. The PLW of the fruits was calculated as cumulative percent loss in weight based on the initial fruit weight and loss in weight recorded at the time of periodical sampling. The firmness of the fruit was measured with the help of Texture Analyzer (Model TA-HDi make, stable Microsystems, UK) having probe speed of 5 mm/s using compression platen (75 mm diameter) and expressed in gram force. Measurements were made at three locations (top, middle and bottom) of each fruit with peel. For colour determination of each sample, the reflectance spectra were measured at 2 different points on the fruit surface and then the mean reflectance spectrum was obtained. These measurements were taken with colour difference meter (model: Mini Scan XE Plus, Hunter Lab, USA) and expressed as L, a, b Hunter colour values (Hunter 1975). Sensory evaluation of cucumbers consisted of preference rating for three sensory characters viz. appearance, flavour and texture by a 10 member trained panel using 9 point Hedonic scale (9 = excellent pleasant, 1 = very poor) for each of four sensory characters as per method described by Amerine et al. (1965). Decay percentage was measured in terms of extent of cucumber spoilage due to shrivelling and softening of fruit ends due to water loss, development of chilling injury symptoms and rotting due to appearance of disease was recorded and the cumulative fruit decay percent was worked out. The experiment was laid out in completely randomized design and each treatment was replicated thrice. The significance among treatment mean values was determined by least significant difference (LSD) at p < 0.05 level.