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Effect of packaging conditions on quality and shelf-life of fresh pointed gourd (Trichosanthes dioica Roxb.) during storage
Food Packaging and Shelf Life 5 (2015) 56–62
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Effect of packaging conditions on quality and shelf-life of fresh pointed gourd (Trichosanthes dioica Roxb.) during storage Nihar R. Sahooa , Lalit M. Balb,* , Uma S. Pala , Dipika Sahooc a b c
Department of Agricultural Processing and Food Engineering, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 751003, India Post Harvest Process and Food Engineering, College of Agriculture, Jawaharlal Nehru Agricultural University, Tikamgarh, Madhya Pradesh 472001, India Department of Horticulture, College of Agriculture, Bhawanipatna, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 751003, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 March 2014 Received in revised form 26 March 2015 Accepted 5 June 2015 Available online xxx
Effect of packaging conditions on shelf-life quality of pointed gourd were studied during ambient (23– 35 C, 45–75% RH) and refrigerated (4–6 C, 45% RH) storage. Six different packaging types i.e. modified atmospheric packaging (MAP) with low density polyethylene (LDPE) film, MAP with polypropylene (PP) film, MAP in LDPE-film with pin holes, MAP in PP-film with pin holes, shrink packaging with bi-axially oriented polypropylene (BOPP) film and vacuum packaging with PP-film techniques were used for experiment. Changes in headspace gas composition, physiological loss in weight (PLW), ascorbic acid, texture, colour and subjective quality of pointed gourd were evaluated periodically during storage. The in-pack modified gaseous composition created a suitable headspace with low O2 and high CO2, which resulted in better retention of freshness and marketability of the vegetables in different packaging conditions. Shrink and vacuum packaging could not yield desired result under ambient storage because of high water vapour transmission rate (WVTR) of film and loss of turgidity. PLW of 5.56(1.52) % was the highest in pointed gourd samples stored in ambient condition upto 4th day of storage, whereas the least (0.34%) in pointed gourd packed with PP-film under refrigerated condition. MAP with PP-film in refrigerated condition was found significantly improved shelf-life of pointed gourd up to 16 days. Ambient conditions could extend shelf-life of pointed gourd up to 4 days using LDPE-film with pin holes. The outcome of the study will have great potential and recommended for fresh fruit and vegetable industry. ã2015 Elsevier Ltd. All rights reserved.
Keywords: Pointed gourd Shelf-life Modified atmosphere packaging Storage Physiological loss in weight Surface colour
1. Introduction Pointed gourd (Trichosanthes dioica) commonly known as parwal is an important tropical vegetable of Indian subcontinent. It is one of the most important cucurbitaceous vegetable due to high nutritional and medicinal values and referred as ‘king of gourds’ (Saha, Das, & Khatua, 2004). It is commercially grown in India, Myanmar, Sri Lanka, Bangladesh and China. The crop is grown during October–November and remains in the field up to September. In India the crop is commonly cultivated in the states of Bihar, Uttar Pradesh, Assam and West Bengal (Nath & Subramanyam, 1972). This vegetable is important sources of different vitamins and minerals. It contains about 255 IU vitamin A, 29 mg vitamin C, 9.0 mg Mg, 2.6 mg Na, 83.0 mg K, 1.1 mg Cu, and 17.0 mg S
* Corresponding author. Fax: +91 674 2562360. E-mail address: [email protected] (L.M. Bal). http://dx.doi.org/10.1016/j.fpsl.2015.06.003 2214-2894/ ã 2015 Elsevier Ltd. All rights reserved.
per 100 g edible part (Singh, 1989). The fruit is cooked in various ways either alone or in combination with other vegetables. However, it has high rates of respiration which results in shorter shelf-life at room temperature due to various physiological factors regulated by genetic mechanisms. The major changes taking place during its storage include loss in weight due to moisture loss, degradation of chlorophyll, change in colour, loss of turgidity, change in texture, loss of nutritional value and reduction in marketability. Fruit surface wrinkling is more prominent in pointed gourd even with a low water loss (Guharoy, Bhattacharyya, Mukherjee, Mandal, & Khatua, 2006). As a general local practice bulk packaging of pointed gourd is done by covering with gunny bag followed by moistening with sprinkling water. But due to unfavourable storage conditions of high temperature and low relative humidity lead to rapid shrivelling, skin and core yellowing, development of hard seeds and fungal infection. Under ambient room temperature storage conditions, pointed gourd has a very short shelf-life of about 3–
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4 days. Depletion of chlorophyll takes place very fast in ambient condition, which results in yellowing of the skin and the pulp which are least accepted and rejected by buyers in the market place (Koley, Asrey, Samuel, & Sasikala, 2009). Different methods of polymeric film packaging of fresh produces have been described by various authors, to increase shelf-life, which include MAP, MAP in perforated (with pin holes) film, vacuum packaging, shrink packaging, cling film wrapping etc. Also reports says that polymeric film packaging in combination with cool storage have been successful employed in delaying senescence, maintenance of physico-chemical constituents and extending shelf-life (Rai & Paul, 2007). Polymeric film packaging along with low temperature storage uses the natural process of respiration of vegetables in conjunction with restricted gas exchange through a barrier (perforated or non-perforated film package) to control in-pack gaseous compositions of O2 and CO2 (Rai & Paul, 2007 Rai, Kaur, & Patil, 2011). However, improper film selection and packaging technique can lead to loss of quality in a very short period. Selection of an appropriate packaging film, package fill weight and temperature are the important conditions to increase the shelf-life of fresh produce. Chakraborty, Kabir, Dhua, and Ray (1991) reported, the shelflife of freshly harvested tender pointed gourd increased by 4 days of storage with almost no shrinkage and low yellowing by dipping in (1900 mg/L) potassium metabisulphite (KMS) solution for 10 min and subsequently air dried and stored in zero energy cool chamber (27–30 C, 94–96 % RH). Chakraborty, Ray, and Kabir (2002) reported that pointed gourd dipped in 1% Semperfresh solution for 10 min and stored at ambient conditions (29–37 C, 64–75 % RH) resulted in the lowest PLW (24.2%) and fruit shrinkage (17.5%), up to 2 days of storage. However, Feygenberg, Hershkovitz, Ben-Aire, Jacob, Pesis, & Nikitenko (2005) reported that Semperfresh is a carbohydrate based formulation which gives poor protection against water. Goswami, Borah, Baishya, Saikia, Deka and Bidyut (2008) developed a low cost storage structures for shelf-life extension of horticultural produces. Koley, Asrey, Pal, and Samuel (2009) found that use of carnuba wax, lower concentration of sodium hypochlorite, potassium metabisulphite restricted respiration rate, PLW and pectin methyl esterase activities. This helped to retain higher level of chlorophyll, hue angle and texture of stored pointed gourds. Sen and Sengupta (2011) worked on extension and maintaining marketable status of shelf-life of pointed gourd using plant growth promoting rhizobacteria in combination with kinetin and gibberellic acid. Singh, Pandey, Pandey, and Yadav (2012) reported that post-harvest treatment could extend shelf-life of vegetables. Patel, Soni, Kabir, and Agrawal (2013) reported wax coating could enhance fruit quality for longer period. Literature review revealed that no attempts have been made so far to uncover a suitable polymeric packaging material and technique to extend the shelf-life of highly perishable pointed gourd. Keeping this in view, the present work has been undertaken to find out the most suitable packaging materials and technique to enhance storage life of pointed gourd, during storage.
57
2. Materials and methods 2.1. Raw material and sample preparation Fresh green pointed gourds were harvested manually at commercial maturity from the research farm of Orissa University of Agriculture and Technology, Bhubaneswar. Immediately after harvest, pointed gourds were transported in plastic crates to the experiment site. Vegetables of uniform size, shape and colour were selected for the study. Over matured and blemished samples were discarded. Samples were air pre-cooled for 2 h at 15 C. Next the vegetables were washed with water containing 0.5% citric acid, and air-cooled again for 2 h for removing the remaining surface moisture. The initial moisture content of the pointed gourd sample was 92.4(0.5)% w.b. 2.2. Packaging conditions and storage Approximately 500 g of pointed gourds were packed in each pack for the experiments. Different packaging techniques used were MAP with LDPE-film, MAP with PP-film, MAP in LDPE-film with pin holes, MAP in PP-film with pin holes, shrink packaging with BOPP-film, vacuum packaging with PP-film. MAP treatment was provided by passive modification. The properties of these films measured at ambient temperature (23–35 C, 45–75% RH) used for packaging experiments is given in Table 1. Bag surface area of 0.625 m2 was provided for each pack. For providing MAP with ventilation condition, five numbers of pinhole perforations of 0.3 mm diameter in each side of LDPE-film and PPfilm were done. MAP was established by the respiration of vegetables inside the packs. Initial gas concentrations were that of the atmosphere environment. Sample packs were stored at ambient (23–35 C and 45–75% RH) and chilled refrigerated (4– 6 C, 45% RH) conditions separately. Control samples of 500 g each were kept unsealed under similar environmental conditions of temperature and RH separately. Three packs each from MAP with LDPE-film, LDPE-film with pin holes, PP-film and PP-film with pin holes were taken out at 1 day interval of storage for analysis of inpack headspace gas concentration of O2 and CO2. The qualitative analysis of the stored sample packages were carried out in triplicate at 2 days interval. 2.3. Physico-chemical analysis 2.3.1. Package headspace gas evaluation Package headspace analysis for O2 and CO2 concentration was carried out by a check point O2/CO2 instrument (PBI Dansensor, Denmark) at prespecified storage interval (Tirkey, Pal, Bal, Sahoo, Bakhara, & Panda, 2014). The apparatus uses a biosensor. A small self adhesive silicon septum is glued to the package and a needle is pierced through this septum into the pack to draw the gas sample. The sensor signals is converted to concentration values of O2 and CO2, which were directly read on the digital display panel of the instrument. The accuracy of the apparatus was 0.1% for O2 and 2% for CO2. The calibration for the instrument has been done with
Table 1 Properties of films used for packaging of pointed gourd.
LDPE film PP film BOPP film
Thickness (m)
Density (g/ cc)
Oxygen transmission rate (cc (STP)/m2/ day/bar)
Water vapor transmission rate (g/m2/ day/bar)
Tensile strength (kg/ cm2)
Elongation (% l/l)
25
0.910
6400
04.50
165
600
45 23
1.054 0.901
3000 4500
07.75 18.00
400 300
300 -
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atmospheric O2 and CO2 concentration. Parameters are expressed as DCO2 and DO2 percentage referred to initial values. 2.3.2. Physiological weight loss The weight of each pointed gourd package sample was measured using a laboratory level electronic weighing balance (Model CA 224, Contech Instruments Ltd., India) having 0.0001 g least count. The PLW was calculated and expressed in percentage based on initial weight of the samples. Cumulative PLW was analysed with respect to different treatments (Sahoo, Bal, Pal, & Sahoo, 2014). 2.3.3. Ascorbic acid analysis Ascorbic acid of pointed gourds were determined by the 2,6dichlorophenol indo phenol titration method (Ranganna, 2004). The ascorbic acid content was calculated from the titration value, dye factor, dilution and volume of the sample and finally expressed as mg/100 g fresh weight (Sahoo, Panda, Bal, Pal, & Sahoo, 2015).
Fig. 1. Changes in head space concentrations of O2 and CO2 under ambient condition.
2.3.4. Texture evaluation Texture analyser (TA-XT Plus, Stable Microsystems Ltd., UK) was used to measure the texture of the pointed gourd samples at regular intervals. 2 mm probe using 50 kg load cell was attached to the instrument to measure the peak force (kgf) to puncture the sample. At least 10 measurements were carried out for each packaging condition and average data has been obtained. 2.3.5. Surface colour evaluation Hunter Lab colorimeter (ColourFlex, Hunter Associates Laboratory, Inc., Virginia, USA) was used to measure the surface colour of the pointed gourd samples equipped with a 12 mm measuring head (Bal, Kar, Satya, & Naik, 2011). Colour was measured using the CIE L, a, b scale and illuminant D65. The instrument was calibrated with black and white reference tiles through the tri-stimulus values X,Y and Z, taking as standard values those of the white background (X = 79.01; Y = 83.96; Z = 86.76) tile. The colour values were expressed as L (whiteness or brightness/darkness), a (redness/greenness) and b (yellowness/blueness) at any time respectively. Since the pointed gourd did not cover the entire surface area, they were scanned at three different locations to determine the average L, a and b values during the measurements. Numerical values of L, a and b were considered for the evaluation of colour modification of the product. At each storage condition, 10 measurements were carried out for each sample from the packages. In addition, value ‘a/b’ was taken as the colour index. 2.3.6. Subjective quality analysis For assessing the marketable quality of the pointed gourd, descriptive quality were determined subjectively by observing the level of visible mould growth, decay, shrivelling, smoothness and shine of the produce by an expert panel consisting of 5 males and 5 females in the age group of 25–60. The number of marketable vegetable was used as a measure to calculate the percentage of marketable vegetable during storage. Marketability of 80% and above was considered as the cut off point for acceptance of the lot and was used as a benchmark for assessment of shelf-life of the product (Mohammed, Wilson, & Gomes, 1999; Tefera, Seyoum, & Woldetsadik, 2007). 2.4. Statistical analyses The results acquired were subjected to analysis of variance (ANOVA) using SPSS 10.0 software. The means obtained from each set were compared using the Duncan’s multiple range test based on a complete randomized design (at 0.05 confidence level).
Fig. 2. Changes in head space concentrations of O2 and CO2 under refrigerated condition.
3. Results and discussion 3.1. Headspace gas The package headspace composition of O2 and CO2 is shown in Figs. 1 and 2. Initially, as the headspace modification started, the produce respired at a faster rate which could be gauged from the rapid fall of in pack O2 and rise of in-pack CO2 respectively. After 1 day of storage in MAP under ambient condition, the in-pack atmosphere arrived at steady state stable level of 9.1(0.52) and 7.8(0.41)% O2 and 6.6 (0.26), 4.9(0.45)% of CO2 for the LDPEfilm and PP-film with pin holes. The O2 level reduced from 22.0 (0.22) to 8.3(0.32)% (LDPE-film) and from 22.0(0.22) to 7.1 (0.62)% (PP-film) in one day and then remained almost constant at 8.3 and 7.1% respectively from day one onwards. CO2 level increased from an initial value of 0 to about 5.8(0.62)% (LDPEfilm) and to 4.5(0.34)% (PP-film) in one day and attained a steady state in both the cases after day one of storage. Under refrigerated condition a similar trend was obtained but the changes were more gradual. The steady state O2 level was about 9.2(0.57), 7.5(0.59), 9.5(0.49) and 5.3(0.37)%, respectively for LDPE-film and PP-film and LDPE-film with pin holes and PP-film with pin holes. The CO2 level measured was found to be lower than those maintained under ambient condition due to low respiration rate at lower temperature storage environment (Cocci, Rocculi, Romani, & Rosa, 2006).
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In ambient storage of vegetables in vacuum pack and shrink pack, initially there was no headspace gas, however after 4 and 8 days of storage there was little gas accumulation and the samples spoiled thereafter. So headspace gas analysis was not done for those samples. In case of refrigerated storage of vegetables, vacuum was maintained in both vacuum pack and shrink pack till 16 days of storage, so no headspace gas analysis was done. 3.2. Physiological weight loss The PLW of the pointed gourd samples subjected to different packaging and storage conditions are shown in Figs. 3 and 4. The PLW in case of pointed gourd was maximum in the ambient control samples, where it was 5.56(1.52)% after 4th day of storage as compared to 6.98(0.82)% in 8th day in refrigerated control. Samples under ambient condition of storage, PLW was observed to be 0.77(0.16) and 0.89(0.17)% in MAP for PP-film and PP-film with pin holes stored samples respectively, whereas slightly higher value of 0.91(0.35)% PLW was recorded for shrink pack samples in 4 days storage. Under refrigerated storage there was no change in weight till 8th day in LDPE-film and PP-film stored samples. The PLW was 0.37(0.25), 0.34(0.06), 0.43(0.09) and 0.50(0.04)% in LDPE-film, PP-film, LDPE-film with pin holes and PP-film with pin holes packs, respectively at the end of 16th days of storage under refrigerated condition. But in case of refrigerated shrink pack storage the PLW was 2.24(0.56)% at 16th day. The higher PLW in shrink pack conditions might be due to the packaging material being BOPP-film, which was having higher WVTR mentioned in Table 1 (Sahoo et al., 2014). This decrease in weight may be attributed to respiration and other senescence related to metabolic processes during storage (Tirkey et al., 2014).
Fig. 4. Changes in PLW% under refrigerated storage.
3.3. Ascorbic acid content The ascorbic acid content decreased with storage period under all the packaging treatments and storage environments. However the changes in ascorbic acid content during storage of pointed gourd were significantly higher in case of ambient storage as compared to refrigerated storage conditions. In the ambient control samples the decrease was the maximum from an initial value of 26.22(1.3)–20.35(1.58) mg/100 g at the end of 4th day of storage (Fig. 5). Pointed gourd stored in LDPE-film with pin holes packs showed highest retention of ascorbic acid (23.54 2.73 mg/ 100 g) at the end of 4th day among the different packaging methods under ambient storage followed by the vacuum pack condition where the decrease was from 26.22(1.3) mg/100 g to 23.25(2.83) mg/100 g. In refrigerated storage control samples the
Fig. 5. Change in ascorbic acid content under ambient storage.
Fig. 6. Change in ascorbic acid content under refrigerated storage.
decrease was from 26.22(1.3) mg/100 g in the 1st day to 24.22 (1.4) mg/100 g of ascorbic acid at the end of 4th day. Among refrigerated storage condition, PP-film with pin holes showed the best result with 25.86(1.6) mg/100 g in the 4th day and decreased to 23.10(2.72) mg/100 g at the end of 16th day of storage followed by vacuum packaging with 24.51(2.17) mg/100 g ascorbic acid in the 4th day to 22.31(2.4) mg/100 g at the end of 16 days of storage (Fig. 6). Fig. 3. Changes in PLW% under ambient storage.
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Table 2 Effect of packaging material and storage environment on texture of pointed gourd. Packaging material
Texture (kgf) Storage period (days) 0
Ambient Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
1.63a(0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35)
Refrigerated Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35)
4
8
12
16
1.61a(0.49) 1.27b(0.28) 1.14b(0.37) 1.35b(0.35) 1.21a(0.46) 1.60ab(0.59) 1.21b(0.47)
– – – 1.25c(0.18) 0.94c(0.52) 1.40c(0.62) 1.02c(0.12)
– – – – – – –
– – – – – – –
1.32b(0.42) 1.33b(0.51) 1.35b(0.36) 1.58a(0.21) 1.56b(0.34) 1.33b(0.56) 1.27b(0.18)
1.18c(0.43) 1.14c(0.34) 1.28c(0.37) 1.26b(0.29) 1.27c(0.35) 1.21c(0.27) 1.16c(0.24)
– 1.05d(0.36) 1.19d(0.25) 1.05c(0.43) 1.02d(0.19) 1.09d(0.28) 0.98d(0.47)
– – 1.13e(0.31) 0.94cd(0.25) 0.99de(0.17) 1.01e(0.52) 0.87e(0.42)
Figures in parenthesis are standard deviation. Values in the same rows followed by different superscript letters (a–f) are significant different (p < 0.05). (LDPE, low density polyethylene, PP, polypropylene).
3.4. Changes in texture A decrease in the peak force required to puncture the pointed gourd samples was observed (Table 2) in all the packaging types both under ambient and refrigerated storage conditions except the ambient stored control samples where there was marginal increase from 1.63 kgf initially to 1.6 kgf at the end of 4th day of storage. This increase may be due to excess loss of moisture from the surface of the samples exposed to the open atmosphere making the tissues in the surface hard. In all other ambient packaging types there was significant decrease in the puncture force. The decrease in peak force was from 1.63 to 0.94 kgf in PP-film with pin holes under ambient storage of 8 days. The control sample showed a decrease of peak force from 1.63 to 1.18 kgf at the end of 8th day under refrigerated storage. The decrease in puncture force was gradual in all other samples stored in different packaging types under refrigerated condition. Samples stored in LDPE-film with pin holes condition maintained the best texture among all the refrigerated stored samples with a value of 1.02 kgf at the 16th day. Singh, Giri, and Kotwaliwale (2014) also reported similar type of result for green bell pepper under active modified atmosphere storage. 3.5. Changes in colour The colour ratio a/b represents comparative colourant strength of the sample being studied in terms of the red colour over yellow colour. More colour ratio value is an indication of more redness of the sample being examined. In control ambient sample there is a drastic colour change with a/b value changing from an initial value of 0.88 to 0.39 in the 4th day (Table 3). The same change was also confirmed from the visual observation of the ambient stored control samples which were completely red at the 4th day of storage. The colour change was gradual and the ‘a’ value changed from ‘ ve’ to ‘+ve’ indicating gradual change in colour to red with the advancement of storage period for all the packages under ambient storage except in the vacuum pack where the ‘a’ value remained ‘ ve’. This was also confirmed from the visual observation of the samples and the colour change from green to red might be due to breakdown of chlorophyll pigments and dominance of other colour pigments like xanthophylls and anthocyanins etc. The a/b value increased gradually in all the
packaging conditions. In refrigerated storage samples the colour change was minimal and no significant change was observed except in the control where the a/b value changed from an initial value of 0.88 to 0.50 in the 8th day of storage. 3.6. Percentage marketability The percentage marketable pointed gourd obtained with duration of storage in different packaging materials and storage environment are shown in Table 4. The control pointed gourds under ambient condition lost marketability very fast, it could stay up to 2 days and at 4 days of storage the marketability reduced to unacceptable level of 64.23%. Slightly better results were obtained under ambient storage with LDPE-film, PP-film, vacuum and shrink where the marketability was reduced to 65.49, 72.79, 71.79 and 71.77%, respectively in 4 days of storage. The samples stored in LDPE-film with pin holes and PP-film with pin holes could remain in marketable condition at 78.35 and 80.39%, respectively up to 4 days but rapidly lost marketability after that. It is observed from Table 4, that the refrigerated condition could enhance the shelf-life of samples in comparison to ambient condition irrespective of the packaging type. Control samples could maintain the marketability (82.59%) up to 4 days of storage. The samples stored in LDPE-film, PP-film, vacuum and shrink pack remained marketable (more than 80%) up to 12 days of storage. Highest marketability (84.38%) of pointed gourd was observed in LDPE-film with pin holes packs after 16 days of storage. The good storage performance of vegetables in terms of marketability in LDPE-film and PP-film with perforation in refrigerated storage could be attributed to the fact that low temperature storage along with modified atmosphere retarded the senescence due to low respiration rate. The packs without any perforation showed higher rotting percentage and water accumulation, which may be due to anaerobic respiration. The performance of vacuum pack and shrink pack was significantly higher under refrigerated condition than that under ambient condition. Sahoo et al. (2015) also reported similar studies in fresh guava packed in MAP and shrink wrap packaging techniques. Though no significant biochemical changes could be observed during the entire storage period, the marketability reduced rapidly in some of the packaging material due to higher rotting percentage (Sahoo et al., 2014).
N.R. Sahoo et al. / Food Packaging and Shelf Life 5 (2015) 56–62 Table 3 Effect of packaging material and storage environment on surface colour of pointed gourd. Packaging material
0 Ambient Control
4
8
12
38.94 9.94 11.26 0.88
22.56 1.25 29.92 0.39
–
–
–
L a b a/b
38.94 9.94 11.26 0.88
35.64 3.81 14.69 0.25
–
–
–
LDPE with pin holes
L a b a/b
38.94 9.94 11.26 0.88
34.58 3.21 30.56 0.10
–
–
–
PP
L a b a/b
38.94 9.94 11.26 0.88
32.56 5.91 17.49 0.33
23.14 5.21 19.87 0.26
–
–
PP with pin holes
L a b a/b
38.94 9.94 11.26 0.88
31.59 0.87 24.56 0.03
27.03 1.39 25.48 0.05
–
–
Vacuum pack
L a b a/b
38.94 9.94 11.26 0.88
32.53 4.66 15.14 0.30
26.17 2.19 17.89 0.12
–
–
Shrink pack
L a b a/b
38.94 9.94 11.26 0.88
25.24 4.48 12.42 0.36
12.41 4.97 15.29 0.32
–
–
L a b a/b
38.94 9.94 11.26 0.88
32.81 9.54 14.32 0.66
29.25 9.24 18.19 0.50
–
–
LDPE
L a b a/b
38.94 9.94 11.26 0.88
35.67 8.85 35.54 0.24
31.42 6.24 33.52 0.18
29.57 5.56 30.12 0.18
–
LDPE with pin holes
L a b a/b
38.94 9.94 11.26 0.88
33.46 8.52 14.56 0.58
31.12 8.11 16.25 0.49
28.58 6.03 20.25 0.29
23.12 5.67 22.53 0.25
PP
L a b a/b
38.94 9.94 11.26 0.88
34.41 9.88 13.65 0.72
31.12 8.87 15.14 0.58
31.57 5.87 18.71 0.31
29.42 4.97 21.68 0.22
PP with pin holes
L a b a/b
38.94 9.94 11.26 0.88
36.15 8.89 13.81 0.64
35.25 7.53 14.45 0.52
33.45 6.21 16.63 0.37
31.52 5.68 17.56 0.32
Vacuum pack
L a b a/b
38.94 9.94 11.26 0.88
35.12 8.63 12.45 0.69
31.83 5.42 14.63 0.37
29.94 5.06 16.54 0.30
25.41 4.48 18.42 0.24
Shrink pack
L a b a/b
38.94 9.94 11.26 0.88
34.57 7.53 13.94 0.54
33.52 5.54 15.56 0.35
30.67 5.16 18.72 0.27
28.43 5.05 20.51 0.24
Refrigerated Control
Marketability (%) Storage period (days) 0
4
8
12
16
Ambient Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
100 100 100 100 100 100 100
44.23 65.49 78.35 72.79 80.39 71.79 71.77
– – – 33.57 32.73 34.37 32.92
– – – – – – –
– – – – – – –
Refrigerated Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
100 100 100 100 100 100 100
82.59 93.89 100 92.56 100 98.43 100
62.14 90.56 94.73 88.76 93.37 87.65 96.73
– 75.30 93.83 81.57 89.15 81.34 89.58
– – 84.38 73.39 78.07 75.11 78.43
16
L a b a/b
LDPE
Table 4 Effect of packaging material and storage environment on the percentage marketability of pointed gourd. Packaging material
Surface colour Storage period (days)
61
4. Conclusion The in-pack pointed gourd created a suitable headspace environment with low O2 and high CO2 concentrations, which resulted in better retention of its freshness and marketability as well. Shrink packaging with BOPP-film could not yield better result under ambient storage because of high WVTR of the film and consequently loss of turgidity of the vegetables. Among different packaging techniques and storage conditions, MAP with PP-film in refrigerated condition was found significantly improved shelf-life of the pointed gourd up to 16 days followed by vacuum pack with PP-film in refrigerated condition keeping its texture, colour, ascorbic acid and marketability intact. Whereas, the ambient conditions could be extend the shelf-life of pointed gourd up to 4 days using LDPE-film with pin holes and PP-film as MAP storage. Commercialization of such innovations might bring large improvements in marketability and consumption of fresh pointed gourd. Furthermore, combination of MAP systems with edible coatings can be a feasible way of improving microbial stability and quality of fresh pointed gourd, thus extending their shelf-life. References Bal, L. M., Kar, A., Satya, S., & Naik, S. N. (2011). Kinetics of color change of bamboo shoot during microwave drying. International Journal of Food Science and Technology., 46, 827–833. Chakraborty, K., Kabir, J., Dhua, R. S., & Ray, S. K. D. (1991). Storage behaviour of pointed gourd under zero energy cool chambers. Horticultural Journal, 4, 43–47. Chakraborty, K., Ray, S. K. D., & Kabir, J. (2002). Influence of semperfresh coating on storage life of pointed gourd (Trichosanthes diocia Hart.). Journal of Interacademicia, 6, 486–489. Cocci, E., Rocculi, P., Romani, S., & Rosa, M. D. (2006). Changes in nutritional properties of minimally processed apples during storage. Postharvest Biology and Technology, 39, 265–271. Rai, D. R., Kaur, P., & Patil, R. T. (2011). Quality changes in fresh-cut capsicum (Capsıcum annuum) shreds under modified atmospheres during simulated retail and home storage. Journal of Food Processing and Preservation, 35, 402–409. Feygenberg, O., Hershkovitz, V., Ben-Aire, R., Jacob, E., Pesis, S., & Nikitenko, T. (2005). Postharvest use of organic coating for maintaining bio-organic avocado and mango quality. Acta Horticulturae, 682, 507–512. Goswami, S., Borah, A., Baishya, S., Saikia, A., Deka, & Bidyut, C. (2008). Low cost storage structures for shelf-life extension of horticultural produces. Journal of Food Science and Technology, 45, 70–74. Guharoy, S., Bhattacharyya, S., Mukherjee, S. K., Mandal, N., & Khatua, D. C. (2006). Phytophthora melonis associated with fruit and vine rot disease of pointed gourd in India as revealed by RFLP and sequencing of ITS region. Journal of Phytopathology, 10, 612–615. Koley, T. K., Asrey, R., Pal, R. K., & Samuel, D. V. K. (2009a). Shelf-life extension in pointed gourd (Trichosanthes dioica Roxb.) by post-harvest application of
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sodium hypochlorite, potassium metabisulphite and carnauba wax. Journal of Food Science and Technology, 46, 581–584. Koley, T. K., Asrey, R., Samuel, D. V. K., & Sasikala, C. (2009b). Careful handling in pointed gourd after picking pays. Indian Horticulture, 54, 44–45. Mohammed, M., Wilson, L. A., & Gomes, P. L. (1999). Post-harvest sensory and physiochemical attributes of processing and non processing tomato cultivar. Journal of Food Quality, 22, 167–182. Nath, P., & Subramanyam, S. (1972). Pointed gourd can be a popular crop. Indian Horticulture, 17, 20–21. Patel, D. R., Soni, A. K., Kabir, J., & Agrawal, N. (2013). Influence of wax coating on shelf-life of pointed gourd (Trichosanthes dioca Roxb.). Karnataka Journal of Agricultural Sciences, 26, 393–398. Rai, D. R., & Paul, S. (2007). Packaging requirements of highly respiring produce under modified atmosphere packaging: a review. Journal of Food Science and Technology, 44, 10–15. Ranganna, S. (2004). Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd ed. Tata McGraw-Hill Publishing Company Limited: New Delhi. Saha, G., Das, S. N., & Khatua, D. (2004). Fruit and vine rot of pointed gourd-etiology, epidemiology and management. Journal of Mycopathology Research, 42, 73–81. Sahoo, N. R., Bal, L. M., Pal, U. S., & Sahoo, D. (2014). A comparative study on the effect of packaging material and storage environment on shelf-life of fresh bellpepper. Journal of Food Measurement and Characterization, 8, 164–170.
Sahoo, N. R., Panda, M. K., Bal, L. M., Pal, U. S., & Sahoo, D. (2015). Comparative study of MAP and shrink wrap packaging techniques for shelf-life extension of fresh Guava. Scientia Horticulturae, 182, 1–7. Sen, K., & Sengupta, C. (2011). Extension of shelf-life of pointed gourd fruits by a novel approach using PGPR. Asian Journal of Experimental Biological Sciences, 2, 422–428. Singh, K. (1989). Pointed gourd (Trichosanthes dioica Roxb.). Indian Horticulture, 33, 35–38. Singh, R., Pandey, P. K., Pandey, A., & Yadav, F. D. (2012). Impact of post-harvest treatment on shelf-life of vegetables. International Journal of Biodiversity and Environment, 2, 186. Singh, R., Giri, S. K., & Kotwaliwale, N. (2014). Shelf-life enhancement of green bell pepper (Capsicum annuum L.) under active modified atmosphere storage. Food Packaging and Shelf Life, 1, 101–112. Tefera, A., Seyoum, T., & Woldetsadik, K. (2007). Effect of disinfection, packaging and storage environment on the shelf-life of mango. Biosystem Engineering, 96, 201– 212. Tirkey, B., Pal, U. S., Bal, L. M., Sahoo, N. R., Bakhara, C. K., & Panda, M. K. (2014). Evaluation of physico-chemical changes of fresh-cut unripe papaya during storage. Food Packaging and Shelf Life, 1, 190–197.
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Food Packaging and Shelf Life journal homepage: http://www.elsevier.com/locate/fpsl
Effect of packaging conditions on quality and shelf-life of fresh pointed gourd (Trichosanthes dioica Roxb.) during storage Nihar R. Sahooa , Lalit M. Balb,* , Uma S. Pala , Dipika Sahooc a b c
Department of Agricultural Processing and Food Engineering, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 751003, India Post Harvest Process and Food Engineering, College of Agriculture, Jawaharlal Nehru Agricultural University, Tikamgarh, Madhya Pradesh 472001, India Department of Horticulture, College of Agriculture, Bhawanipatna, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 751003, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 March 2014 Received in revised form 26 March 2015 Accepted 5 June 2015 Available online xxx
Effect of packaging conditions on shelf-life quality of pointed gourd were studied during ambient (23– 35 C, 45–75% RH) and refrigerated (4–6 C, 45% RH) storage. Six different packaging types i.e. modified atmospheric packaging (MAP) with low density polyethylene (LDPE) film, MAP with polypropylene (PP) film, MAP in LDPE-film with pin holes, MAP in PP-film with pin holes, shrink packaging with bi-axially oriented polypropylene (BOPP) film and vacuum packaging with PP-film techniques were used for experiment. Changes in headspace gas composition, physiological loss in weight (PLW), ascorbic acid, texture, colour and subjective quality of pointed gourd were evaluated periodically during storage. The in-pack modified gaseous composition created a suitable headspace with low O2 and high CO2, which resulted in better retention of freshness and marketability of the vegetables in different packaging conditions. Shrink and vacuum packaging could not yield desired result under ambient storage because of high water vapour transmission rate (WVTR) of film and loss of turgidity. PLW of 5.56(1.52) % was the highest in pointed gourd samples stored in ambient condition upto 4th day of storage, whereas the least (0.34%) in pointed gourd packed with PP-film under refrigerated condition. MAP with PP-film in refrigerated condition was found significantly improved shelf-life of pointed gourd up to 16 days. Ambient conditions could extend shelf-life of pointed gourd up to 4 days using LDPE-film with pin holes. The outcome of the study will have great potential and recommended for fresh fruit and vegetable industry. ã2015 Elsevier Ltd. All rights reserved.
Keywords: Pointed gourd Shelf-life Modified atmosphere packaging Storage Physiological loss in weight Surface colour
1. Introduction Pointed gourd (Trichosanthes dioica) commonly known as parwal is an important tropical vegetable of Indian subcontinent. It is one of the most important cucurbitaceous vegetable due to high nutritional and medicinal values and referred as ‘king of gourds’ (Saha, Das, & Khatua, 2004). It is commercially grown in India, Myanmar, Sri Lanka, Bangladesh and China. The crop is grown during October–November and remains in the field up to September. In India the crop is commonly cultivated in the states of Bihar, Uttar Pradesh, Assam and West Bengal (Nath & Subramanyam, 1972). This vegetable is important sources of different vitamins and minerals. It contains about 255 IU vitamin A, 29 mg vitamin C, 9.0 mg Mg, 2.6 mg Na, 83.0 mg K, 1.1 mg Cu, and 17.0 mg S
* Corresponding author. Fax: +91 674 2562360. E-mail address: [email protected] (L.M. Bal). http://dx.doi.org/10.1016/j.fpsl.2015.06.003 2214-2894/ ã 2015 Elsevier Ltd. All rights reserved.
per 100 g edible part (Singh, 1989). The fruit is cooked in various ways either alone or in combination with other vegetables. However, it has high rates of respiration which results in shorter shelf-life at room temperature due to various physiological factors regulated by genetic mechanisms. The major changes taking place during its storage include loss in weight due to moisture loss, degradation of chlorophyll, change in colour, loss of turgidity, change in texture, loss of nutritional value and reduction in marketability. Fruit surface wrinkling is more prominent in pointed gourd even with a low water loss (Guharoy, Bhattacharyya, Mukherjee, Mandal, & Khatua, 2006). As a general local practice bulk packaging of pointed gourd is done by covering with gunny bag followed by moistening with sprinkling water. But due to unfavourable storage conditions of high temperature and low relative humidity lead to rapid shrivelling, skin and core yellowing, development of hard seeds and fungal infection. Under ambient room temperature storage conditions, pointed gourd has a very short shelf-life of about 3–
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4 days. Depletion of chlorophyll takes place very fast in ambient condition, which results in yellowing of the skin and the pulp which are least accepted and rejected by buyers in the market place (Koley, Asrey, Samuel, & Sasikala, 2009). Different methods of polymeric film packaging of fresh produces have been described by various authors, to increase shelf-life, which include MAP, MAP in perforated (with pin holes) film, vacuum packaging, shrink packaging, cling film wrapping etc. Also reports says that polymeric film packaging in combination with cool storage have been successful employed in delaying senescence, maintenance of physico-chemical constituents and extending shelf-life (Rai & Paul, 2007). Polymeric film packaging along with low temperature storage uses the natural process of respiration of vegetables in conjunction with restricted gas exchange through a barrier (perforated or non-perforated film package) to control in-pack gaseous compositions of O2 and CO2 (Rai & Paul, 2007 Rai, Kaur, & Patil, 2011). However, improper film selection and packaging technique can lead to loss of quality in a very short period. Selection of an appropriate packaging film, package fill weight and temperature are the important conditions to increase the shelf-life of fresh produce. Chakraborty, Kabir, Dhua, and Ray (1991) reported, the shelflife of freshly harvested tender pointed gourd increased by 4 days of storage with almost no shrinkage and low yellowing by dipping in (1900 mg/L) potassium metabisulphite (KMS) solution for 10 min and subsequently air dried and stored in zero energy cool chamber (27–30 C, 94–96 % RH). Chakraborty, Ray, and Kabir (2002) reported that pointed gourd dipped in 1% Semperfresh solution for 10 min and stored at ambient conditions (29–37 C, 64–75 % RH) resulted in the lowest PLW (24.2%) and fruit shrinkage (17.5%), up to 2 days of storage. However, Feygenberg, Hershkovitz, Ben-Aire, Jacob, Pesis, & Nikitenko (2005) reported that Semperfresh is a carbohydrate based formulation which gives poor protection against water. Goswami, Borah, Baishya, Saikia, Deka and Bidyut (2008) developed a low cost storage structures for shelf-life extension of horticultural produces. Koley, Asrey, Pal, and Samuel (2009) found that use of carnuba wax, lower concentration of sodium hypochlorite, potassium metabisulphite restricted respiration rate, PLW and pectin methyl esterase activities. This helped to retain higher level of chlorophyll, hue angle and texture of stored pointed gourds. Sen and Sengupta (2011) worked on extension and maintaining marketable status of shelf-life of pointed gourd using plant growth promoting rhizobacteria in combination with kinetin and gibberellic acid. Singh, Pandey, Pandey, and Yadav (2012) reported that post-harvest treatment could extend shelf-life of vegetables. Patel, Soni, Kabir, and Agrawal (2013) reported wax coating could enhance fruit quality for longer period. Literature review revealed that no attempts have been made so far to uncover a suitable polymeric packaging material and technique to extend the shelf-life of highly perishable pointed gourd. Keeping this in view, the present work has been undertaken to find out the most suitable packaging materials and technique to enhance storage life of pointed gourd, during storage.
57
2. Materials and methods 2.1. Raw material and sample preparation Fresh green pointed gourds were harvested manually at commercial maturity from the research farm of Orissa University of Agriculture and Technology, Bhubaneswar. Immediately after harvest, pointed gourds were transported in plastic crates to the experiment site. Vegetables of uniform size, shape and colour were selected for the study. Over matured and blemished samples were discarded. Samples were air pre-cooled for 2 h at 15 C. Next the vegetables were washed with water containing 0.5% citric acid, and air-cooled again for 2 h for removing the remaining surface moisture. The initial moisture content of the pointed gourd sample was 92.4(0.5)% w.b. 2.2. Packaging conditions and storage Approximately 500 g of pointed gourds were packed in each pack for the experiments. Different packaging techniques used were MAP with LDPE-film, MAP with PP-film, MAP in LDPE-film with pin holes, MAP in PP-film with pin holes, shrink packaging with BOPP-film, vacuum packaging with PP-film. MAP treatment was provided by passive modification. The properties of these films measured at ambient temperature (23–35 C, 45–75% RH) used for packaging experiments is given in Table 1. Bag surface area of 0.625 m2 was provided for each pack. For providing MAP with ventilation condition, five numbers of pinhole perforations of 0.3 mm diameter in each side of LDPE-film and PPfilm were done. MAP was established by the respiration of vegetables inside the packs. Initial gas concentrations were that of the atmosphere environment. Sample packs were stored at ambient (23–35 C and 45–75% RH) and chilled refrigerated (4– 6 C, 45% RH) conditions separately. Control samples of 500 g each were kept unsealed under similar environmental conditions of temperature and RH separately. Three packs each from MAP with LDPE-film, LDPE-film with pin holes, PP-film and PP-film with pin holes were taken out at 1 day interval of storage for analysis of inpack headspace gas concentration of O2 and CO2. The qualitative analysis of the stored sample packages were carried out in triplicate at 2 days interval. 2.3. Physico-chemical analysis 2.3.1. Package headspace gas evaluation Package headspace analysis for O2 and CO2 concentration was carried out by a check point O2/CO2 instrument (PBI Dansensor, Denmark) at prespecified storage interval (Tirkey, Pal, Bal, Sahoo, Bakhara, & Panda, 2014). The apparatus uses a biosensor. A small self adhesive silicon septum is glued to the package and a needle is pierced through this septum into the pack to draw the gas sample. The sensor signals is converted to concentration values of O2 and CO2, which were directly read on the digital display panel of the instrument. The accuracy of the apparatus was 0.1% for O2 and 2% for CO2. The calibration for the instrument has been done with
Table 1 Properties of films used for packaging of pointed gourd.
LDPE film PP film BOPP film
Thickness (m)
Density (g/ cc)
Oxygen transmission rate (cc (STP)/m2/ day/bar)
Water vapor transmission rate (g/m2/ day/bar)
Tensile strength (kg/ cm2)
Elongation (% l/l)
25
0.910
6400
04.50
165
600
45 23
1.054 0.901
3000 4500
07.75 18.00
400 300
300 -
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atmospheric O2 and CO2 concentration. Parameters are expressed as DCO2 and DO2 percentage referred to initial values. 2.3.2. Physiological weight loss The weight of each pointed gourd package sample was measured using a laboratory level electronic weighing balance (Model CA 224, Contech Instruments Ltd., India) having 0.0001 g least count. The PLW was calculated and expressed in percentage based on initial weight of the samples. Cumulative PLW was analysed with respect to different treatments (Sahoo, Bal, Pal, & Sahoo, 2014). 2.3.3. Ascorbic acid analysis Ascorbic acid of pointed gourds were determined by the 2,6dichlorophenol indo phenol titration method (Ranganna, 2004). The ascorbic acid content was calculated from the titration value, dye factor, dilution and volume of the sample and finally expressed as mg/100 g fresh weight (Sahoo, Panda, Bal, Pal, & Sahoo, 2015).
Fig. 1. Changes in head space concentrations of O2 and CO2 under ambient condition.
2.3.4. Texture evaluation Texture analyser (TA-XT Plus, Stable Microsystems Ltd., UK) was used to measure the texture of the pointed gourd samples at regular intervals. 2 mm probe using 50 kg load cell was attached to the instrument to measure the peak force (kgf) to puncture the sample. At least 10 measurements were carried out for each packaging condition and average data has been obtained. 2.3.5. Surface colour evaluation Hunter Lab colorimeter (ColourFlex, Hunter Associates Laboratory, Inc., Virginia, USA) was used to measure the surface colour of the pointed gourd samples equipped with a 12 mm measuring head (Bal, Kar, Satya, & Naik, 2011). Colour was measured using the CIE L, a, b scale and illuminant D65. The instrument was calibrated with black and white reference tiles through the tri-stimulus values X,Y and Z, taking as standard values those of the white background (X = 79.01; Y = 83.96; Z = 86.76) tile. The colour values were expressed as L (whiteness or brightness/darkness), a (redness/greenness) and b (yellowness/blueness) at any time respectively. Since the pointed gourd did not cover the entire surface area, they were scanned at three different locations to determine the average L, a and b values during the measurements. Numerical values of L, a and b were considered for the evaluation of colour modification of the product. At each storage condition, 10 measurements were carried out for each sample from the packages. In addition, value ‘a/b’ was taken as the colour index. 2.3.6. Subjective quality analysis For assessing the marketable quality of the pointed gourd, descriptive quality were determined subjectively by observing the level of visible mould growth, decay, shrivelling, smoothness and shine of the produce by an expert panel consisting of 5 males and 5 females in the age group of 25–60. The number of marketable vegetable was used as a measure to calculate the percentage of marketable vegetable during storage. Marketability of 80% and above was considered as the cut off point for acceptance of the lot and was used as a benchmark for assessment of shelf-life of the product (Mohammed, Wilson, & Gomes, 1999; Tefera, Seyoum, & Woldetsadik, 2007). 2.4. Statistical analyses The results acquired were subjected to analysis of variance (ANOVA) using SPSS 10.0 software. The means obtained from each set were compared using the Duncan’s multiple range test based on a complete randomized design (at 0.05 confidence level).
Fig. 2. Changes in head space concentrations of O2 and CO2 under refrigerated condition.
3. Results and discussion 3.1. Headspace gas The package headspace composition of O2 and CO2 is shown in Figs. 1 and 2. Initially, as the headspace modification started, the produce respired at a faster rate which could be gauged from the rapid fall of in pack O2 and rise of in-pack CO2 respectively. After 1 day of storage in MAP under ambient condition, the in-pack atmosphere arrived at steady state stable level of 9.1(0.52) and 7.8(0.41)% O2 and 6.6 (0.26), 4.9(0.45)% of CO2 for the LDPEfilm and PP-film with pin holes. The O2 level reduced from 22.0 (0.22) to 8.3(0.32)% (LDPE-film) and from 22.0(0.22) to 7.1 (0.62)% (PP-film) in one day and then remained almost constant at 8.3 and 7.1% respectively from day one onwards. CO2 level increased from an initial value of 0 to about 5.8(0.62)% (LDPEfilm) and to 4.5(0.34)% (PP-film) in one day and attained a steady state in both the cases after day one of storage. Under refrigerated condition a similar trend was obtained but the changes were more gradual. The steady state O2 level was about 9.2(0.57), 7.5(0.59), 9.5(0.49) and 5.3(0.37)%, respectively for LDPE-film and PP-film and LDPE-film with pin holes and PP-film with pin holes. The CO2 level measured was found to be lower than those maintained under ambient condition due to low respiration rate at lower temperature storage environment (Cocci, Rocculi, Romani, & Rosa, 2006).
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In ambient storage of vegetables in vacuum pack and shrink pack, initially there was no headspace gas, however after 4 and 8 days of storage there was little gas accumulation and the samples spoiled thereafter. So headspace gas analysis was not done for those samples. In case of refrigerated storage of vegetables, vacuum was maintained in both vacuum pack and shrink pack till 16 days of storage, so no headspace gas analysis was done. 3.2. Physiological weight loss The PLW of the pointed gourd samples subjected to different packaging and storage conditions are shown in Figs. 3 and 4. The PLW in case of pointed gourd was maximum in the ambient control samples, where it was 5.56(1.52)% after 4th day of storage as compared to 6.98(0.82)% in 8th day in refrigerated control. Samples under ambient condition of storage, PLW was observed to be 0.77(0.16) and 0.89(0.17)% in MAP for PP-film and PP-film with pin holes stored samples respectively, whereas slightly higher value of 0.91(0.35)% PLW was recorded for shrink pack samples in 4 days storage. Under refrigerated storage there was no change in weight till 8th day in LDPE-film and PP-film stored samples. The PLW was 0.37(0.25), 0.34(0.06), 0.43(0.09) and 0.50(0.04)% in LDPE-film, PP-film, LDPE-film with pin holes and PP-film with pin holes packs, respectively at the end of 16th days of storage under refrigerated condition. But in case of refrigerated shrink pack storage the PLW was 2.24(0.56)% at 16th day. The higher PLW in shrink pack conditions might be due to the packaging material being BOPP-film, which was having higher WVTR mentioned in Table 1 (Sahoo et al., 2014). This decrease in weight may be attributed to respiration and other senescence related to metabolic processes during storage (Tirkey et al., 2014).
Fig. 4. Changes in PLW% under refrigerated storage.
3.3. Ascorbic acid content The ascorbic acid content decreased with storage period under all the packaging treatments and storage environments. However the changes in ascorbic acid content during storage of pointed gourd were significantly higher in case of ambient storage as compared to refrigerated storage conditions. In the ambient control samples the decrease was the maximum from an initial value of 26.22(1.3)–20.35(1.58) mg/100 g at the end of 4th day of storage (Fig. 5). Pointed gourd stored in LDPE-film with pin holes packs showed highest retention of ascorbic acid (23.54 2.73 mg/ 100 g) at the end of 4th day among the different packaging methods under ambient storage followed by the vacuum pack condition where the decrease was from 26.22(1.3) mg/100 g to 23.25(2.83) mg/100 g. In refrigerated storage control samples the
Fig. 5. Change in ascorbic acid content under ambient storage.
Fig. 6. Change in ascorbic acid content under refrigerated storage.
decrease was from 26.22(1.3) mg/100 g in the 1st day to 24.22 (1.4) mg/100 g of ascorbic acid at the end of 4th day. Among refrigerated storage condition, PP-film with pin holes showed the best result with 25.86(1.6) mg/100 g in the 4th day and decreased to 23.10(2.72) mg/100 g at the end of 16th day of storage followed by vacuum packaging with 24.51(2.17) mg/100 g ascorbic acid in the 4th day to 22.31(2.4) mg/100 g at the end of 16 days of storage (Fig. 6). Fig. 3. Changes in PLW% under ambient storage.
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Table 2 Effect of packaging material and storage environment on texture of pointed gourd. Packaging material
Texture (kgf) Storage period (days) 0
Ambient Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
1.63a(0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35) 1.63a (0.35)
Refrigerated Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35) 1.63a(0.35)
4
8
12
16
1.61a(0.49) 1.27b(0.28) 1.14b(0.37) 1.35b(0.35) 1.21a(0.46) 1.60ab(0.59) 1.21b(0.47)
– – – 1.25c(0.18) 0.94c(0.52) 1.40c(0.62) 1.02c(0.12)
– – – – – – –
– – – – – – –
1.32b(0.42) 1.33b(0.51) 1.35b(0.36) 1.58a(0.21) 1.56b(0.34) 1.33b(0.56) 1.27b(0.18)
1.18c(0.43) 1.14c(0.34) 1.28c(0.37) 1.26b(0.29) 1.27c(0.35) 1.21c(0.27) 1.16c(0.24)
– 1.05d(0.36) 1.19d(0.25) 1.05c(0.43) 1.02d(0.19) 1.09d(0.28) 0.98d(0.47)
– – 1.13e(0.31) 0.94cd(0.25) 0.99de(0.17) 1.01e(0.52) 0.87e(0.42)
Figures in parenthesis are standard deviation. Values in the same rows followed by different superscript letters (a–f) are significant different (p < 0.05). (LDPE, low density polyethylene, PP, polypropylene).
3.4. Changes in texture A decrease in the peak force required to puncture the pointed gourd samples was observed (Table 2) in all the packaging types both under ambient and refrigerated storage conditions except the ambient stored control samples where there was marginal increase from 1.63 kgf initially to 1.6 kgf at the end of 4th day of storage. This increase may be due to excess loss of moisture from the surface of the samples exposed to the open atmosphere making the tissues in the surface hard. In all other ambient packaging types there was significant decrease in the puncture force. The decrease in peak force was from 1.63 to 0.94 kgf in PP-film with pin holes under ambient storage of 8 days. The control sample showed a decrease of peak force from 1.63 to 1.18 kgf at the end of 8th day under refrigerated storage. The decrease in puncture force was gradual in all other samples stored in different packaging types under refrigerated condition. Samples stored in LDPE-film with pin holes condition maintained the best texture among all the refrigerated stored samples with a value of 1.02 kgf at the 16th day. Singh, Giri, and Kotwaliwale (2014) also reported similar type of result for green bell pepper under active modified atmosphere storage. 3.5. Changes in colour The colour ratio a/b represents comparative colourant strength of the sample being studied in terms of the red colour over yellow colour. More colour ratio value is an indication of more redness of the sample being examined. In control ambient sample there is a drastic colour change with a/b value changing from an initial value of 0.88 to 0.39 in the 4th day (Table 3). The same change was also confirmed from the visual observation of the ambient stored control samples which were completely red at the 4th day of storage. The colour change was gradual and the ‘a’ value changed from ‘ ve’ to ‘+ve’ indicating gradual change in colour to red with the advancement of storage period for all the packages under ambient storage except in the vacuum pack where the ‘a’ value remained ‘ ve’. This was also confirmed from the visual observation of the samples and the colour change from green to red might be due to breakdown of chlorophyll pigments and dominance of other colour pigments like xanthophylls and anthocyanins etc. The a/b value increased gradually in all the
packaging conditions. In refrigerated storage samples the colour change was minimal and no significant change was observed except in the control where the a/b value changed from an initial value of 0.88 to 0.50 in the 8th day of storage. 3.6. Percentage marketability The percentage marketable pointed gourd obtained with duration of storage in different packaging materials and storage environment are shown in Table 4. The control pointed gourds under ambient condition lost marketability very fast, it could stay up to 2 days and at 4 days of storage the marketability reduced to unacceptable level of 64.23%. Slightly better results were obtained under ambient storage with LDPE-film, PP-film, vacuum and shrink where the marketability was reduced to 65.49, 72.79, 71.79 and 71.77%, respectively in 4 days of storage. The samples stored in LDPE-film with pin holes and PP-film with pin holes could remain in marketable condition at 78.35 and 80.39%, respectively up to 4 days but rapidly lost marketability after that. It is observed from Table 4, that the refrigerated condition could enhance the shelf-life of samples in comparison to ambient condition irrespective of the packaging type. Control samples could maintain the marketability (82.59%) up to 4 days of storage. The samples stored in LDPE-film, PP-film, vacuum and shrink pack remained marketable (more than 80%) up to 12 days of storage. Highest marketability (84.38%) of pointed gourd was observed in LDPE-film with pin holes packs after 16 days of storage. The good storage performance of vegetables in terms of marketability in LDPE-film and PP-film with perforation in refrigerated storage could be attributed to the fact that low temperature storage along with modified atmosphere retarded the senescence due to low respiration rate. The packs without any perforation showed higher rotting percentage and water accumulation, which may be due to anaerobic respiration. The performance of vacuum pack and shrink pack was significantly higher under refrigerated condition than that under ambient condition. Sahoo et al. (2015) also reported similar studies in fresh guava packed in MAP and shrink wrap packaging techniques. Though no significant biochemical changes could be observed during the entire storage period, the marketability reduced rapidly in some of the packaging material due to higher rotting percentage (Sahoo et al., 2014).
N.R. Sahoo et al. / Food Packaging and Shelf Life 5 (2015) 56–62 Table 3 Effect of packaging material and storage environment on surface colour of pointed gourd. Packaging material
0 Ambient Control
4
8
12
38.94 9.94 11.26 0.88
22.56 1.25 29.92 0.39
–
–
–
L a b a/b
38.94 9.94 11.26 0.88
35.64 3.81 14.69 0.25
–
–
–
LDPE with pin holes
L a b a/b
38.94 9.94 11.26 0.88
34.58 3.21 30.56 0.10
–
–
–
PP
L a b a/b
38.94 9.94 11.26 0.88
32.56 5.91 17.49 0.33
23.14 5.21 19.87 0.26
–
–
PP with pin holes
L a b a/b
38.94 9.94 11.26 0.88
31.59 0.87 24.56 0.03
27.03 1.39 25.48 0.05
–
–
Vacuum pack
L a b a/b
38.94 9.94 11.26 0.88
32.53 4.66 15.14 0.30
26.17 2.19 17.89 0.12
–
–
Shrink pack
L a b a/b
38.94 9.94 11.26 0.88
25.24 4.48 12.42 0.36
12.41 4.97 15.29 0.32
–
–
L a b a/b
38.94 9.94 11.26 0.88
32.81 9.54 14.32 0.66
29.25 9.24 18.19 0.50
–
–
LDPE
L a b a/b
38.94 9.94 11.26 0.88
35.67 8.85 35.54 0.24
31.42 6.24 33.52 0.18
29.57 5.56 30.12 0.18
–
LDPE with pin holes
L a b a/b
38.94 9.94 11.26 0.88
33.46 8.52 14.56 0.58
31.12 8.11 16.25 0.49
28.58 6.03 20.25 0.29
23.12 5.67 22.53 0.25
PP
L a b a/b
38.94 9.94 11.26 0.88
34.41 9.88 13.65 0.72
31.12 8.87 15.14 0.58
31.57 5.87 18.71 0.31
29.42 4.97 21.68 0.22
PP with pin holes
L a b a/b
38.94 9.94 11.26 0.88
36.15 8.89 13.81 0.64
35.25 7.53 14.45 0.52
33.45 6.21 16.63 0.37
31.52 5.68 17.56 0.32
Vacuum pack
L a b a/b
38.94 9.94 11.26 0.88
35.12 8.63 12.45 0.69
31.83 5.42 14.63 0.37
29.94 5.06 16.54 0.30
25.41 4.48 18.42 0.24
Shrink pack
L a b a/b
38.94 9.94 11.26 0.88
34.57 7.53 13.94 0.54
33.52 5.54 15.56 0.35
30.67 5.16 18.72 0.27
28.43 5.05 20.51 0.24
Refrigerated Control
Marketability (%) Storage period (days) 0
4
8
12
16
Ambient Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
100 100 100 100 100 100 100
44.23 65.49 78.35 72.79 80.39 71.79 71.77
– – – 33.57 32.73 34.37 32.92
– – – – – – –
– – – – – – –
Refrigerated Control LDPE LDPE with pin holes PP PP with pin holes Vacuum pack Shrink pack
100 100 100 100 100 100 100
82.59 93.89 100 92.56 100 98.43 100
62.14 90.56 94.73 88.76 93.37 87.65 96.73
– 75.30 93.83 81.57 89.15 81.34 89.58
– – 84.38 73.39 78.07 75.11 78.43
16
L a b a/b
LDPE
Table 4 Effect of packaging material and storage environment on the percentage marketability of pointed gourd. Packaging material
Surface colour Storage period (days)
61
4. Conclusion The in-pack pointed gourd created a suitable headspace environment with low O2 and high CO2 concentrations, which resulted in better retention of its freshness and marketability as well. Shrink packaging with BOPP-film could not yield better result under ambient storage because of high WVTR of the film and consequently loss of turgidity of the vegetables. Among different packaging techniques and storage conditions, MAP with PP-film in refrigerated condition was found significantly improved shelf-life of the pointed gourd up to 16 days followed by vacuum pack with PP-film in refrigerated condition keeping its texture, colour, ascorbic acid and marketability intact. Whereas, the ambient conditions could be extend the shelf-life of pointed gourd up to 4 days using LDPE-film with pin holes and PP-film as MAP storage. Commercialization of such innovations might bring large improvements in marketability and consumption of fresh pointed gourd. Furthermore, combination of MAP systems with edible coatings can be a feasible way of improving microbial stability and quality of fresh pointed gourd, thus extending their shelf-life. References Bal, L. M., Kar, A., Satya, S., & Naik, S. N. (2011). Kinetics of color change of bamboo shoot during microwave drying. International Journal of Food Science and Technology., 46, 827–833. Chakraborty, K., Kabir, J., Dhua, R. S., & Ray, S. K. D. (1991). Storage behaviour of pointed gourd under zero energy cool chambers. Horticultural Journal, 4, 43–47. Chakraborty, K., Ray, S. K. D., & Kabir, J. (2002). Influence of semperfresh coating on storage life of pointed gourd (Trichosanthes diocia Hart.). Journal of Interacademicia, 6, 486–489. Cocci, E., Rocculi, P., Romani, S., & Rosa, M. D. (2006). Changes in nutritional properties of minimally processed apples during storage. Postharvest Biology and Technology, 39, 265–271. Rai, D. R., Kaur, P., & Patil, R. T. (2011). Quality changes in fresh-cut capsicum (Capsıcum annuum) shreds under modified atmospheres during simulated retail and home storage. Journal of Food Processing and Preservation, 35, 402–409. Feygenberg, O., Hershkovitz, V., Ben-Aire, R., Jacob, E., Pesis, S., & Nikitenko, T. (2005). Postharvest use of organic coating for maintaining bio-organic avocado and mango quality. Acta Horticulturae, 682, 507–512. Goswami, S., Borah, A., Baishya, S., Saikia, A., Deka, & Bidyut, C. (2008). Low cost storage structures for shelf-life extension of horticultural produces. Journal of Food Science and Technology, 45, 70–74. Guharoy, S., Bhattacharyya, S., Mukherjee, S. K., Mandal, N., & Khatua, D. C. (2006). Phytophthora melonis associated with fruit and vine rot disease of pointed gourd in India as revealed by RFLP and sequencing of ITS region. Journal of Phytopathology, 10, 612–615. Koley, T. K., Asrey, R., Pal, R. K., & Samuel, D. V. K. (2009a). Shelf-life extension in pointed gourd (Trichosanthes dioica Roxb.) by post-harvest application of
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