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Storability, shelf-life and quality assurance of sugar snap peas (cv. super sugar snap) using modified atmosphere packaging
Postharvest Biology and Technology 100 (2014) 205–211
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Storability, shelf-life and quality assurance of sugar snap peas (cv. super sugar snap) using modified atmosphere packaging Mohammed M.W. Elwan a, *, Ibrahim N. Nasef a , Samir K. El-Seifi a , Mahmoud A. Hassan a , Rawia E. Ibrahim b a b
Department of Horticulture, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt Vegetable Handling Research Department, Agriculture Research Center, Giza, Egypt
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 July 2014 Received in revised form 14 October 2014 Accepted 17 October 2014
This investigation was aimed at selecting the most suitable package to maintain quality of sugar snap peas pods. The effectiveness of five types of polypropylene packages: highly perforated (HPPP), nonperforated (NPPP) and micro-perforated with 6, 12 and 24 holes (MPPP6, MPPP12 and MPPP24) on storability of pods was studied during cold storage at 0 C with 90–95% RH for 7, 14, 21 days and simulating shelf-life conditions at10 C with 80–85% RH for 2 or 4 days after 21 days at 0 C. O2 and CO2 concentrations, weight loss, visual quality, off odors, decay, color, firmness, crispness, taste, total chlorophyll, vitamin C, SSC, and total sugar contents were measured. Results revealed that O2 decreased and CO2 increased slowly inside MPPP6, MPPP12 and MPPP24 bags, however, the reduction in O2 and the increments in CO2 in NPPP bags were very sharp and accompanied with high levels of off odors. HPPP had the highest weight loss compared with other bags. MPPP12 bags maintained quality during storage and simulated shelf-life, in terms of higher scores for visual quality, firmness, crispness and taste as well as highest contents of chlorophyll, vitamin C and sugars. NPPP bags had the worst values for quality. At the end of storage and shelf-life, an increment in h* was observed in samples stored in MPPP6, MPPP12 and MPPP24 bags (more green color) in comparison with those in NPPP bags. ã 2014 Elsevier B.V. All rights reserved.
Keywords: Sugar snap peas Modified atmosphere packaging Microperforated polypropylene bag Cold storage Shelf-life Quality
1. Introduction Sugar snap peas (Pisum sativum L. var. saccharatum) are a new type of pea in Egypt, sown for export. They play an important role in human nutrition as a cheap source of protein, carbohydrates, vitamins, minerals and other nutrients. Edible-podded peas are harvested before physiological maturity is reached to retain their quality. Shortly after harvest, loss of sweetness and crispness, degreening and the development of mealiness may decrease quality. Kader (1992) stated that peas are a highly perishable immature commodity that can be cooled and stored at temperatures near 0 C to extend shelf-life. They have a very high respiration rate and are classified as a non-climacteric commodity. All types of peas can be stored for 1–2 weeks at 0 C and 95–98% RH (Suslow and Cantwell, 1998). The benefits of modified atmosphere packaging (MAP) are in extending shelf-life of products to meet market demand through reduction of metabolic activities and pathological deterioration. MAP vastly improves moisture retention by maintaining a higher
* Corresponding author. Tel.: +20 64 3481057. E-mail address: [email protected] (M.M.W. Elwan). http://dx.doi.org/10.1016/j.postharvbio.2014.10.006 0925-5214/ ã 2014 Elsevier B.V. All rights reserved.
RH around the fruit inside the sealed package, with an influence on preserving quality (Mangaraj et al., 2012). Passive modified atmosphere packaging is a technology that can be employed through the use of polymeric films with different numbers and dimensions of microperforations. Storability and shelf-life, as well as quality of fruit and vegetables, are affected by type, thickness and perforation of films used in MAP (Serrano et al., 2006; Simon et al., 2008; Jia et al., 2009; Simon and Gonzalez-Fandos, 2011; Selcuk and Erkan, 2014). Serrano et al. (2006) found that broccoli packaged in microperforated polypropylene film had prolonged storability up to 28 days with high quality attributes and health-promoting compounds. A micro-perforated polyethylene film with 2 holes extended shelf-life and reduced postharvest deterioration of broccoli florets stored at 4 and 20 C (Jia et al., 2009). Microperforated polypropylene films with 7 and 9 holes (90 mm) maintained strawberry quality during cold storage (Kartal et al., 2012). Packages with perforated areas of 1.57, 3.14 and 4.71 mm2 can be used to preserve strawberry quality for 10 days at 2 C (Sanz et al., 2002). Also, Almenar et al. (2007) reported that microperforated films with one and three perforations maintained the chemical, physical and sensory qualities of strawberries.
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Little information is available on passive modified atmosphere packaging of sugar snap peas. Sugar snap peas are exported from Egypt in highly perforated polypropylene traditional bags. This bag maintains visual quality for a maximum of 1–2 weeks. So, the peas are exported by air, which is very expensive. The main objective of the present investigation was to evaluate the influence of passive MAP by using perforated polypropylene (control), non-perforated polypropylene and three new microperforated polypropylene films with 6, 12 and 24 holes, on the changes in several parameters related to sugar snap pea quality during cold storage and shelf-life. A further aim of this work was to reduce the transportation costs by using sea freight instead of air through a prolonged storage period. 2. Materials and methods
A panel of five trained judges (members of Vegetable Handling Research Department, Horticulture Research Institute, Agricultural Research Center, Egypt) evaluated the visual quality of all pods from each bag at the end of each storage period and subsequent shelf-life. Visual appearance was scored on a 9 to 1 scale, where 9 = excellent and fresh appearance, 7 = good, 5 = fair (limited marketability), 3 = poor and 1 = unusable, according to Jimenez et al. (1998). Pod surface color was evaluated on 6 pods from each bag using a Hunter colorimeter (Hunter Instrument DP-9000, Japan) which measures L*, a*, b*, C* and h*. Higher positive hue values indicate green color. A color wheel subtends 360 , with red–purple traditionally placed at the far right (or at an angle of 0 ); yellow, bluish–green, and blue follow counterclockwise at 90 , 180 , and 270 , respectively as reported by McGuire (1992).
2.1. Plant materials and packaging treatments
2.4. Firmness, crispness, taste and off odors.
Sugar snap peas (P. sativum L. var. saccharatum cv. ‘super sugar snap’) was planted in winter of 2011–2012 (from 2nd October to 5th March) at the Experimental Research Farm, Faculty of Agriculture, Suez Canal University, Ismailia Governorate, Egypt, to produce the pods of sugar snap peas. Fresh pods were harvested by hand at the appropriate stage of maturity according to El-Seifi et al. (2014), on February 9, 2012 and transported to the laboratory of the Vegetable Handling Research Department, Horticulture Research Institute, ARC, Ministry of Agriculture, Egypt within 3 h. Pods were inspected and sound pods were held for 12 h at 0–2 C and 90–95% RH, then the tops and tail of the pods were cut, and the pods sorted and graded according to export criteria prior to packaging (Suslow and Cantwell, 1998). Fresh pods (250 g) were packed into five different types of polypropylene bags and sealed, with overall bags dimensions of 17 15 cm. Highly perforated bags (HPPP; obtained from El-Huda Company, Ismailia, Egypt), were 30 mm in thickness and with 1800 holes (1000 mm in diameter), commonly used for export in Egypt. The other bags (45 mm in thickness with 550 mm hole diameters) (obtained from ICOPACK Company, 6th of October, Giza, Egypt) were non-perforated bags (NPPP), micro-perforated bags with 6 holes (MPPP6), 12 holes (MPPP12) and 24 holes (MPPP24). Micro-holes were made in the bags using a 550 mm diameter cold needle (Watkins and Thompson, 1992). The bags were placed in 5 kg carton boxes (26 W 40 L 12 H) cm and stored at 0 1 C, with 90–95% RH for 21 days. After 7, 14 and 21 days of storage, 6 bags (a replicate) from each treatment were transferred to an evaluation room. To simulate commercial storage and marketing, 12 bags after 21 days at 0 C were kept sealed for 2 and 4 additional days (6 bags for each period) at 10 C and 80–85% RH, then transferred to the evaluation room for the same assessment.
Firmness was evaluated by pressing the pod (six pods from each bag) between the thumb. A scale of 5–1 was used; 5 (firm and turgid), 4 (firm), 3 (moderately firm), 2 (limp and shriveled) and 1 (more limp and shriveled). Panelists rated sugar snap peas for crispness by bending to break the pod (six pods from each bag), on a scale of 5–1; 5 (fully typical), 4 (moderately full), 3 (moderate), 2 (slight) and 1 (none) (El-Bassiouny, 2003). Panelists rated the taste of six pods from each bag on a scale of 5–1, where 5 (fully typical), 4 (moderately full), 3 (moderate), 2 (slight) and 1 (none) (Kader et al., 1973). Off odors of 6 bags from each treatment was evaluated on a scale of 5–1, where 5 (severe), 4 (moderately severe), 3 (moderate), 2 (slight) and 1 (none) (Kasmire et al., 1974). 2.5. Total chlorophyll content Total chlorophylls were extracted from fresh pods (0.5 g tissue from the center of the pods) by acetone (80%) and determined spectrophotometrically according to Lichenthaler and Wellburn (1983), and expressed as mg/100 g fresh weight. 2.6. Ascorbic acid content 10 g of pods tissue for each bag were ground thoroughly in a mortar with 40 ml of 4% oxalic acid solution. The mixture was poured into a 100 mL volumetric flask which was then filled with 4% oxalic acid solution and filtered through a filter paper (Whatman no. 1). Afterwards, 10 mL of supernatant were titrated to a permanent pink color by 0.1% 2,6-dichlorophenolindophenol. Ascorbic acid was calculated according to the titration volume of 2,6-dichlorophenolindophenol and expressed as mg/100 g fresh weight (Pearson, 1970).
2.2. O2 and CO2 concentrations 2.7. Total sugars and soluble solids contents The O2 and CO2 concentrations inside bag headspace during storage were analyzed using a DualTrak Model 902D gas analyzer (Quantek Instruments, USA) before opening. The headspace atmosphere within the 6 removal bags from each storage period was sampled using a syringe inserted through a septum. 2.3. Weight loss, visual quality, decay and color All bags were weighed at zero time and at the end of each storage period and at subsequent shelf-life, 6 bags were reweighed. The weight loss was determined and expressed as percent loss from initial weight.
5 g of fresh pods from each bag for each storage and subsequent shelf-life period were homogenized in 50 mL of 80% ethanol for 2 min and then refluxed for 30 min. The samples were centrifuged at 10,000 g for 30 min. The residue was again subjected to ethanol extraction. The extracts were combined and alcohol was removed by evaporation. An aliquot was taken and then made up to 50 mL with distilled water. Total sugars were measured with phenol–sulfuric acid reagents spectrophotometrically at 480 nm according to Dubois et al. (1956). Soluble solids content (SSC) were measured by hand refractometer according to AOAC (1996) and expressed as %.
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after 21 days of cold storage and 4 days at 10 C (p 0.001). Significant weight loss occurred during prolonged storage periods at 0 C and 10 C in HPPP bags. MPPP6, MPPP12, MPPP24 and NPPP bags had strongly reduced weight loss compared to the HPPP bags. During the storage and shelf-life periods (21 days at 0 C and 4 days at 10 C), the HPPP bag lost 4.38% of its weight while pea pods in MPPP6, MPPP12, MPPP24 and NPPP bags lost between 0.6% and 0.75% of their initial weight (Table 1). The appearance of the pods packed in HPPP were scored as good for marketability after 21 days of cold storage and also were at the limit of marketability after 2 days of shelf-life storage, which was lost when shelf-life was extended to 4 days. However, pods packed in NPPP bags lost their limit of marketability (poor) after 21 days of cold storage and were scored as unacceptable during shelf-life. The pods packed in MPPP12 bags kept their excellent and fresh appearance after 21 days of cold storage plus 2 days of shelf-life, then were scored as good for marketability when the shelf-life period was extended to 4 days. However, MPPP6 and MPPP24 bags maintained excellent and fresh appearance of pods during cold storage only, then scored at the limit for marketability at the end of shelf-life (Table 1). At the end of storage and shelf-life periods, no decay was observed for any packaging treatment (data not shown). External color of the pods was significantly affected by different gas concentrations within the packages. Pods packed in NPPP bags had the lowest h* values (more yellowing) in comparison to other packages after 21 days at cold storage plus 4 days at shelf-life storage. However, micro-perforated bags maintained the green color of pods even more than at harvest (Table 1).
2.8. Statistical analysis The experiments were organized in a completely randomized block design (CRBD) with a split plot arrangement, with six replications (bags), in which each replication was considered as a block. The bag treatments were randomly distributed in the main plots and the storage periods were randomly distributed in the sub-plots. Experimental data were analyzed by analysis of variance (ANOVA) using CoStat version 6.303 1998–2004 CoHort software, 798 Lighthouse Ave, PMP 320, Monterey, CA 93940, USA. Duncan’s test was used to compare means at the 5% significance level. Standard error (SE) of means were calculated for presentation in figures using SigmaPlot version 10.0 (Systat Software Inc., Hounslow, UK) 3. Results 3.1. O2 and Co2 concentrations During storage, headspace O2 concentration significantly decreased in all packages. The O2 concentration decreased sharply from 16.8% to 1.23% in NPPP bags during the first 7 days of storage, then increased up to 5.17% at the end of storage and shelf-life. However, O2 concentrations in MPPP6, MPPP12 and MPPP24 bags decreased to 11.97, 14.12 and 14.77%, respectively, while the HPPP bag maintained the highest O2 concentration (15.58%) at the end of storage and shelf-life. The CO2 concentration increased quickly for NPPP bags in the first week from 0.1% to 52.17% (the highest CO2 concentration), then declined by the end of storage plus shelf-life to 27.7%. The CO2 concentrations inside MPPP6, MPPP12 and MPPP24 bags were about 4%, 1.5% and 0.7% after 7 days of cold storage and by the end of storage and shelf-life the concentrations were slightly increased to 9.8%, 3.9% and 1.8%, respectively. However, HPPP bags showed no change in CO2 concentration during all storage and shelf-life periods (Fig. 1a and b).
3.3. Firmness, crispness, taste and off odors Firmness, crispness, taste and off odors were significantly affected by MAP, storage time and their interaction after 21 days of cold storage and 4 days at 10 C (p 0.001). Pods packed in HPPP kept their firmness, crispiness and taste (firm, turgid and fully typical) only up to 14 days of cold storage and after 21 days of cold storage plus 4 days shelf-life, the scores values ranged between 2.33 and 2.67 (limp, shriveled and slight) which was unacceptable for marketing. However, pods in MPPP12 bags were firm, turgid and fully typical (score; 5) during the cold storage period plus
3.2. Weight loss, visual quality and color There were significant effects of MAP application, storage time and their interaction on weight loss, visual appearance and color
a
207
b
18
o
(0 C)
o
(10 C)
50
(0oC)
(10oC)
CO 2 concentration (%)
O2 concentration (%)
16
14
12
HPPP NPPP MPPP6 MPPP12 MPPP24
6
4
40 HPPP NPPP MPPP6 MPPP12 MPPP24
30 10
2
0 0
0
7
14 21 21+2 Storage period (days)
21+4
0
7
14 21 21+2 Storage period (days)
21+4
Fig. 1. Changes O2 (a) and CO2 (b) concentrations inside MAP during cold storage (0 C) and simulating shelf life at 10 C. Vertical lines represent the standard deviation. Samples size = 6.
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Table 1 Weight loss, visual appearance, h* values of cv. super sugar snap peas after cold storage at 0 C and simulating shelf life at 10 C. Package treatments
Cold storage plus shelf life periods (days)
At harvest
HPPP 21 21
NPPP 21 21
MPPP6 21 21
MPPP12 21 21
MPPP24 21 21
0.0 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4
Significance Package treatments (P) Storage + shelf life (S) PS
Weight loss (%)
Visual appearance (index number)
h*
0.00 1.88d 1.94d 3.60c 3.79b 4.38a 0.31lm 0.41ijkl 0.59fgh 0.61fg 0.66ef 0.26m 0.33klm 0.43ijk 0.50ghi 0.60fg 0.26m 0.36klm 0.48hij 0.56fgh 0.66ef 0.31lm 0.38 jkl 0.51ghi 0.60fg 0.75e
9.00 9.00a 9.00a 7.00b 5.00c 3.00d 9.00a 7.00b 3.00d 1.00e 1.00e 9.00a 9.00a 9.00a 7.00b 5.00c 9.00a 9.00a 9.00a 9.00a 7.00b 9.00a 9.00a 9.00a 7.00b 5.00c
119.05 119.09i 120.76a 120.50ab 120.39abc 120.25a–f 119.63f–i 119.85c–h 117.55j 117.50j 114.15k 119.69e–h 120.29a–e 120.13a–f 120.25a–f 119.93b–h 119.74d–h 119.81c–h 120.20a–f 119.91b–h 120.13a–f 119.34hi 119.48ghi 120.07b–g 120.02b–g 120.35a–d
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The values within a column with different letters are significantly different at p 0.001% according to the Duncan’s multiple range test.
2 days as shelf-life, then scored as firm and moderately full (score; around 4) when the shelf-life period was extended to 4 days. At the end of cold storage (21 days) at 0 C without shelf-life, the pods packed in NPPP bags were unacceptable for marketing (scores; <3) and after the shelf-life period (4 days) the pods were destroyed and wasted. This package showed an increase in off odors with prolongation of cold storage and shelf-life periods, reaching the severe score (4.67), however no off-odors were detected in the other bags (Table 2). 3.4. Chlorophyll content Generally, a degradation in chlorophyll was observed in all packaging treatments. Samples stored in NPPP bags had the lowest chlorophyll values at the start of the storage period (7 days) compared with the other bags. At the end of cold storage and shelflife, MPPP12 bags maintained the highest chlorophyll levels, followed by MPPP24 bags (Table 2). 3.5. Vitamin C Vitamin C content of sugar snap peas was increased (up to 78 mg/100 g) after 7 days of cold storage comped with values at harvest (71.37 mg/100 g) in all samples stored in all bags, except the HPPP bag. At the end of cold storage (21 days), a reduction in the ascorbic acid was observed; this reduction was higher in NPPP bags (approx. 58%). At the end of cold storage and shelf-life, the highest content of ascorbic acid (54 mg/100 g) was measured in samples stored in MPPP12 bags. However, the lowest vitamin C (23.13 mg/100 g) was measured in NPPP (Table 2).
3.6. Total sugar and soluble solids contents There were significant effects of MAP application, storage time and their interaction on total soluble sugars content and soluble solids content (SSC) after 21 days of cold storage and 4 days at 10 C (p 0.001). A negligible changes (69–71.55 mg/g FW) in sugar contents were detected after initial cold storage (7 days) in samples stored in MPPP6, MPPP12 and MPPP24 in comparison with at harvest (70.51 mg/g FW), however, in NPPP samples, the sugar contents were reduced by 10%. At the end of cold storage and shelflife, samples stored in MPPP12 had the highest total sugar content (61.09 mg/g) followed by MPPP24 and MPPP6 (58.82–59.07 mg/g FW), then HPPP (57.23 mg/g FW). However, a sharp reduction (40.85 mg/g FW) in total sugars was observed in samples stored in NPPP bags (Table 2). At the end of cold storage and shelf-life at 10 C, SSC significantly improved from 13.5% to around 17% in pods bagged in MPPP6, MPPP12 and MPPP24, followed by HPPP bags (15.5%). However, a sharp decline in SSC (10.58%) was observed in pods stored in NPPP bags at the end of cold storage and shelf-life periods (Table 2). 4. Discussion Peas are a highly perishable product and shelf-life and visual quality greatly depend on storage conditions such as temperature and atmosphere composition (Kader, 1992; Pariasca et al., 2001). Our results showed that cooling (0 C) and/or modified atmospheres created by MPPP12 (14.12% O2 and 3.9% CO2) greatly extended the cold storage and shelf-life of snap peas, in comparison with HPPP and NPPP bags. The atmosphere
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Table 2 Off odor, firmness, crispness, taste, total chlorophyll, vitamin C and total sugars of cv. super sugar snap peas after cold storage at 0 C and simulating shelf life at 10 C. Index number Package treatments
Cold storage plus shelf life periods (days)
At harvest
HPPP 21 21
NPPP 21 21
MPPP6 21 21
MPPP12 21 21
MPPP24 21 21 Significance Package treatments (P) Storage + shelf life (S) PS
0.0 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4
mg/100 g FW
mg/g FW
Off odor
Firmness
Crispness
Taste
Total chlorophyll
Vitamin C
SSC (%)
Total sugars
1.00 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 2.00d 3.00c 4.00b 4.67a 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e
5.00 5.00a 5.00a 4.00b 3.17c 2.33d 5.00a 4.00b 3.00c 2.00e 1.00f 5.00a 5.00a 5.00a 4.00b 3.17c 5.00a 5.00a 5.00a 5.00a 4.00b 5.00a 5.00a 5.00a 4.00b 3.83b
5.00 5.00a 5.00a 4.00c 3.00e 2.67f 5.00a 4.00c 2.67f 1.00g 1.00g 5.00a 5.00a 5.00a 4.33b 3.67d 5.00a 5.00a 5.00a 5.00a 4.67a 5.00a 5.00a 5.00a 4.33b 3.67d
5.00 5.00a 5.00a 4.00bc 3.50d 2.50e 5.00a 4.00bc 2.50e 1.00f 1.00f 5.00a 5.00a 4.33b 4.00bc 3.83c 5.00a 5.00a 5.00a 4.00bc 4.00bc 5.00a 5.00a 4.67a 4.00bc 3.5d
12.11 11.70a 10.67bcd 10.09d–g 8.86hi 8.81hi 9.445gh 8.10i 7.05j 6.91j 7.09j 11.178abc 10.30d–g 8.84hi 10.36c–f 9.77efg 11.35ab 10.42c–f 10.05d–g 10.10d–g 10.53b–f 11.76a 10.66b–e 9.74fg 10.45c–f 10.09d–g
71.37 70.76ef 70.53f 64.21gh 52.53jk 51.60kl 78.13a 62.78gh 33.04m 31.98m 23.13n 75.07bc 74.23bcd 71.17ef 62.44h 49.66l 75.74b 72.30def 64.91g 57.19i 54.50j 75.68b 72.96cde 62.18h 53.19jk 52.87jk
12.62 13.50f 15.17cd 15.72bc 15.48bc 15.52bc 13.83ef 13.33f 11.72g 11.17gh 10.58h 13.87ef 14.83cd 16.60a 16.72a 16.75a 14.5de 15.42c 16.80a 16.55a 17.00a 14.83cd 15.25cd 16.33ab 16.92a 17.03a
70.51 67.65cd 64.73ef 60.96i–l 60.51jkl 57.23m 63.31fgh 60.97i–l 57.27m 44.71n 40.85o 69.00bc 65.91de 62.20ghij 61.55ghij 58.82lm 71.55a 67.60cd 63.77efg 63.77efg 61.10h–k 70.32ab 67.02cd 63.23f–i 62.78fg–j 59.07klm
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*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
The values within a column with different letters are significantly different at p 0.001% according to the Duncan’s multiple range test.
composition within the packages depended on the number, diameter of the holes and the thickness of the film used. The results indicated an increment of CO2 (except HPPP; unchanged) and a reduction in O2 during prolonged storage time, depending on type of packaging. This result has a number of similarities with results of Kartal et al. (2012) who found that CO2 accumulation and O2 depletion were dependent on perforation surface. In our investigation, the reduction of O2 and the increase of CO2 were within an acceptable range for pod preservation, since good freshness, excellent crispness (fully typical) and no off odors was detected in MPPP12 bags. The favorable effects of MPPP6, MPPP12 and MPPP24 bags regarding crispness may be due to maintaining cell wall strength, cell-cell adhesion, turgidity of cells with retardation of senescence processes and lower respiration rates influenced by gas composition inside the packaging (Escalona et al., 2007b). Similarly El-Bassiouny (2003) with green beans, Escalona et al. (2004) with fennel and Escalona et al. (2007a) with kohlrabi found that micro-perforated films resulted in high firmness values. NPPP bags (45 mm) had the highest CO2 (27.7%) and the lowest O2 (5.17%) levels compared with other bags, and this may be due to high respiration rates of the tested sugar snap peas. This result was similar to results of Lucera et al. (2011) who reported that it is possible that high barrier films enable faster CO2 accumulation and O2 consumption in the package. Hansen et al. (2001) reported that levels of CO2 over 20% induced anaerobic metabolism with generation of off odors mainly due to acetaldehyde of ethanol. Also, Almenar et al. (2007) concluded that low O2 concentrations in non-perforated packages cause breakdown of tissue and off flavor development. Significant differences were observed among the five different packages. MPPP12 (45 mm and 12 holes with 550 mm) preserved the sugar snap pea pods with good visual appearance, firmness,
fully typical for crispness and moderately full for taste (acceptable) at the end of 21 days cold storage and 4 days stimulating shelf conditions. These results are in accordance with the results of Sakaldas et al. (2010) and Fernandez-Leon et al. (2013a,b); Fernandez-Leon et al. (2013a,b) who found that controlled atmosphere and low-density polyethylene based modified atmosphere packaging had the best visual quality for dill and broccoli, respectively. However, HPPP (30 mm and 1800 holes with 1000 mm) kept the pods with good, firm and moderately full visual quality, firmness, crispiness and taste (acceptable) at the end of cold storage (21 days) only, and when packages were transferred to shelf conditions up to 4 days at 10 C, the pods appeared unacceptable for marketing (limp and shriveled for firmness and slight for crispness). Tissue yellowing is an important factor in quality deterioration in stored green vegetables such as sugar snap peas. In our study, the gas composition within the investigated packages significantly affected the external pod color. Micro-perforated (approx. 14% O2 and 4% CO2) packages kept the green color of the pods, giving product acceptability for commercial purposes. On the other hand, h* decreased at significant levels in samples stored in NPPP bags (5.17% O2 and 27.7% CO2), which is a good indicator for decreasing green color. As reported before in snow peas, when h* values decrease, a reduction in green color and increment in yellow color occurs (Pariasca et al., 2001). There is a relationship between color parameters and chlorophyll content, where our data showed that pods stored in MPPP12 bags retained the highest chlorophyll content at the end of storage and shelf-life periods. Also, the faster loss in chlorophyll content was recorded in samples stored in NPPP bags, and this reduction may be due to chlorophyll degradation under the influence of high levels of CO2. Our results are in agreement with Sakaldas et al. (2010) who found that
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modified atmosphere packaging retarded the reduction of chlorophyll content in dill. Also, these results were in accordance with Nath et al. (2011) who found that micro-perforated polypropylene packages retained the highest broccoli chlorophyll content.
loss more than HPPP bags and prevented off odors better than NPPP bags.
In our study, a noticeable weight loss was observed in the HPPP bag during the entire storage and shelf-life periods. However, the weight loss was significantly reduced in MPPP6,MPPP12, MPPP24 and NPPP bags in comparison with the HPPP bag. This could be due to the effect of lower number of microholes as well as smaller microhole diameter on increasing water vapor pressure around the material, and in turn, reduction of the transpiration rate. Also, this effect may be in part due to the thickness, whereas the thickness of MPPP6, MPPP12, MPPP24 and NPPP bags was 45 mm and the HPPP bag 30 mm, which would have increased the transpiration rate.
Association of Official Analytical Chemists, 1996. Official Methods of Analysis. Association of Official Analytical Chemists, Washington, D.C. Albuquerque, B., Lidon, F.C., Barreiro, M.G., 2005. A case study of tendral winter melons (Cucumis melo L.) post harvest senescence. Gen. Appl. Plant Physiol. 31, 157–169. Almenar, E., Del-Valle, V., Hernandez-Munoz, P., Lagaron, J.M., Catala, R., Gavara, R., 2007. Equilibrium modified atmosphere packaging of wild strawberries. J. Sci. Food Agric. 87, 1931–1939. Bodelon, O.G., Sanchez-Ballesta, Blanch M., Escribano, M.T., Merodio, M.I., 2010. The effects of high CO2 levels on anthocyanin composition, antioxidant activity and soluble sugar content of strawberries stored at low non-freezing temperature. Food Chem. 122, 673–678. Del-Valle, V., Hernandez-Munoz, P., Catala, R., Gavara, R., 2009. Optimization of an equilibrium modified atmosphere packaging (EMAP) for minimally processed mandarin segments. J. Food Eng. 91, 474–481. Dubois, M.K.A., Hamilton, J.K., Rebers, P.A., Smith, F., 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28, 350–356. El-Bassiouny, R.E.I., 2003. Modified atmosphere polyethylene packages maintain the quality of snap bean pods during storage. J. Agric. Sci. Mansoura Univ. 28, 3869–3888. El-Seifi, S.K., Hassan, M.A., Ibrahim, Rawia E., Elwan, M.W.M., Nasef, I.N., 2014. Effect of maturity stage on physical and chemical characteristics and determination of harvest time of sugar snap pea pods. J. Plant Prod. Mansoura Univ. 2, 305–314. Escalona, V.H., Aguayo, E., Artes, F., 2007a. Extending the shelf life of kohlrabi stems by modified atmosphere packaging. J. Food Sci. 72, 308–313. Escalona, V.H., Aguayo, E., Artes, F., 2007b. Modified atmosphere packaging improved quality of kohlrabi stems. Food Sci. Technol. 40, 397–403. Escalona, V.H., Aguayo, E., Gomez, P., Artes, F., 2004. Modified atmosphere packaging inhibits browning in fennel. Food Sci. Technol. 37, 115–121. Fernandez-Leon, M.F., Fernandez-Leon, A.M., Lozano, M., Ayuso, M.C., GonzalezGomez, D., 2013a. Altered commercial controlled atmosphere storage conditions for ‘Parhenon’ broccoli plants (Brassica oleracea L. var. italica). Influence on the outer quality parameters and on the health-promoting compounds. Food Sci. Technol. 50, 665–672. Fernandez-Leon, M.F., Fernandez-Leon, A.M., Lozano, M., Ayuso, M.C., GonzalezGomez, D., 2013b. Different postharvest strategies to preserve broccoli quality during storage and shelf life: controlled atmosphere and 1-MCP. Food Chem. 138, 564–573. Hansen, M.E., Sorensen, H., Cantwell, M., 2001. Changes in acetaldehyde, ethanol and amino acid concentrations in broccoli florets during air and controlled atmosphere storage. Postharvest Biol. Technol. 22, 227–237. Jacob, R.A., Sotoudeh, G., 2002. Vitamin C function and status in chronic disease. Nutr. Clin. Care 5, 66–74. Jia, C.G., Xu, C.J., Wei, J., Yuan, J., Yuan, G.F., Wang, B.L., Wang, Q.M., 2009. Effect of modified atmosphere packaging on visual quality and glucosinolates of broccoli florets. Food Chem. 114, 28–37. Jimenez, M., Trijo, E., Cantewell, M., 1998. Postharvest Quality Changes in Green Bean. Research Report. U.C. Davis Cooperative Extension Service, pp. 9. Kader, A.A., 1992. Postharvest biology and technology: an overview and modified atmosphere during transport and storage. In: Kader, A.A. (Ed.), Postharvest Technology of Horticultural Crops. University of California, Publication 3311, USA pp. 15–17, 85–92. Kader, A.A., Lipton, W.J., Morris, L.L., 1973. Systems for scoring quality of harvested lettuce. HortScience 8, 408–409. Kartal, S., Aday, M.S., Caner, C., 2012. Use of microperforated films and oxygen scavengers to maintain storage stability of fresh strawberries. Postharvest Biol. Technol. 71, 32–40. Kasmire, R.F., Kader, A.A., Klaustermeyer, J.A., 1974. Influence of aeration rate and atmospheric composition during simulated transit on visual quality and off odor production by broccoli. HortScience 9, 228–229. Kinyuru, J.N., Kahenya, K.P., Muchui, M., Mungai, H., 2011. Influence of post-harvest handling on the quality of snap bean (Phaseolus vulgaris L.). J. Agric. Food Technol. 1, 43–46. Lichenthaler, H.K., Wellburn, W.R., 1983. Determination of total carotenoids and chlorophylls a and b of leaf extracts in different solvents. Biochem. Soc. Trans. 11, 591–592. Lucera, A., Conte, A., Del Nobile, M.A., 2011. Shelf life of fresh-cut green beans as affected by packaging systems. Int. J. Food Sci. Technol. 46, 2351–2357. McGuire, R.G., 1992. Reporting of objective colour measurements. HortScience 27, 1254–1255. Mangaraj, S., Goswami, T.K., Giri, S.K., Tripathi, M.K., 2012. Permselective MA packaging of litchi (cv: Shahi) for preserving quality and extension of shelf-life. Postharvest Biol. Technol. 71, 1–12. Mapson, C.W., 1970. Vitamins in fruits: stability of L-ascorbic acid. Biochemistry of Fruits and Their Products. Academic Press, London, pp. 376–387. Nath, A., Bagchi, B., Misra, L.K., Deka, B.C., 2011. Changes in post-harvest phytochemical qualities of broccoli florets during ambient and refrigerated storage. Food Chem. 127, 1510–1514.
Several studies have shown that the consumption of foods rich in vitamin C are associated with a decreased risk of several chronic diseases, including cardiovascular disease and cancer (Jacob and Sotoudeh, 2002). Generally in our investigation, vitamin C was reduced by prolongation of storage and shelf-life periods. This reduction may be due to oxidizing enzymes, e.g., ascorbic acid oxidase that reduces the ascorbic acid of the fruit and vegetables, as reported by Mapson (1970) and converts it to dehydroascorbic acid (Albuquerque et al., 2005). However higher ascorbic acid preservation (approx. 70–76%) associated with HPPP, MPPP6, MPPP12 and MPPP24 may be related to the limitation of atmospheric oxygen for oxidation. Similar trends were reported by Pariasca et al. (2001) for snow peas, Kinyuru et al. (2011) for snap beans and Fernandez-Leon et al. (2013a,b); Fernandez-Leon et al. (2013a,b) for broccoli. SSC increased in samples stored in MPPP followed by HPPP packages with the prolongation of storage. Similar results were reported by Fernandez-Leon et al. (2013b) who indicated that SSC in broccoli increased with the prolongation of storage. Our findings seem to be in accordance with Kartal et al. (2012), who showed that perforated films resulted in higher SSC contents than nonperforated polypropylene with strawberries. It is possible that low SSC values of NPPP films are due to the effect of less oxygen and more carbon dioxide in the packages, reflecting a high respiration rate (Del-Valle et al., 2009). Another possible explanation is that high CO2 concentrations inside NPPP packages triggered hydrolysis and glycolysis reactions, resulting in consumption of sugars as reported by Bodelon et al. (2010). In the same direction, data presented herein showed that pods stored in MPPP12 bag maintained the highest values of total sugar contents. Our findings were not due to low weight loss, because the lower weight loss was also detected in NPPP bags, but this results may be due to low respiration rates which would retard loss of sugar. Also, this small reduction in total sugars in desirable bags (MPPP) may be due to normal senescence processes which continue during the storage period, resulting in a reduction of sugar contents as reported before in snow peas (Pariasca et al., 2001). However, the sharp reduction in measured total sugars of samples stored in NPPP bags may be due to higher respiration (higher CO2%) rates associated with consumption of sugars. In conclusion, by controlling the number of holes and their diameter as well as the thickness of polypropylene films, it could be possible to extend cold storage of sugar snap peas for 3 weeks and preserve their good appearance during shelf-life conditions for 4 days. Through the equilibrium of O2 and CO2 (14% O2 and 4% CO2) in MPPP12 bags, the visual quality, color, firmness, crispness, taste, SSC, vitamin C and sugars contents maintained high values in comparison to NPPP and HPPP bags. MPPP bags reduced the weight
References
M.M.W. Elwan et al. / Postharvest Biology and Technology 100 (2014) 205–211 Pariasca, J.A.T., Miyazaki, T., Hisaka, H., Nakagawa, H., Sato, T., 2001. Effect of modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage on the quality of snow pea pods (Pisum sativum L. var. saccharatum). Postharvest Biol. Technol. 21, 213–223. Pearson, D., 1970. The Chemical Analysis of Foods, 6th ed. T.A. Constable, London. Sakaldas, M., Aslım, A.Ş., Kuzucu, C.O., Kaynas, K., 2010. The effects of modified atmosphere packaging and storage temperature on quality and biochemical properties of dill (Anethum graveolens) leaves. J. Food Agric. Environ. 8, 21– 25. Sanz, C., Olias, R., Perez, A.G., 2002. Quality assessment of strawberries packed with perforated polypropylene punnets during cold storage. Food Sci. Technol. Int. 8, 65–71. Selcuk, N., Erkan, M., 2014. Changes in antioxidant activity and postharvest quality of sweet pomegranates cv. Hicrannar under modified atmosphere packaging. Postharvest Biol. Technol. 92, 29–36.
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Serrano, M., Martinez-Romero, D., Guillen, F., Castillo, S., Valero, D., 2006. Maintenance of broccoli quality and functional properties during cold storage as affected by modified atmosphere packaging. Postharvest Biol. Technol. 39, 61–68. Simon, A., Gonzalez-Fandos, E., 2011. Influence of modified atmosphere packaging and storage temperature on the sensory and microbiological quality of fresh peeled white asparagus. Food Control 22, 369–374. Simon, A., Gonzalez-Fandos, E., Rodriguez, D., 2008. Effect of film and temperature on the sensory, microbiological and nutritional quality of minimally processed cauliflower. Int. J. Food Sci. Technol. 43, 1628–1636. Suslow, T.V., Cantwell, M., 1998. Peas – snow and snap pod peas. Perishables Handling Quarterly, 93. University of California, Davis, CA, pp. 15–16. Watkins, C.B., Thompson, C.J., 1992. An evaluation of microperforated polyethylene film bags for storage of ‘Cox’s Orange Pippin’ apples. Postharvest Biol. Technol. 2, 89–100.
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Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio
Storability, shelf-life and quality assurance of sugar snap peas (cv. super sugar snap) using modified atmosphere packaging Mohammed M.W. Elwan a, *, Ibrahim N. Nasef a , Samir K. El-Seifi a , Mahmoud A. Hassan a , Rawia E. Ibrahim b a b
Department of Horticulture, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt Vegetable Handling Research Department, Agriculture Research Center, Giza, Egypt
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 July 2014 Received in revised form 14 October 2014 Accepted 17 October 2014
This investigation was aimed at selecting the most suitable package to maintain quality of sugar snap peas pods. The effectiveness of five types of polypropylene packages: highly perforated (HPPP), nonperforated (NPPP) and micro-perforated with 6, 12 and 24 holes (MPPP6, MPPP12 and MPPP24) on storability of pods was studied during cold storage at 0 C with 90–95% RH for 7, 14, 21 days and simulating shelf-life conditions at10 C with 80–85% RH for 2 or 4 days after 21 days at 0 C. O2 and CO2 concentrations, weight loss, visual quality, off odors, decay, color, firmness, crispness, taste, total chlorophyll, vitamin C, SSC, and total sugar contents were measured. Results revealed that O2 decreased and CO2 increased slowly inside MPPP6, MPPP12 and MPPP24 bags, however, the reduction in O2 and the increments in CO2 in NPPP bags were very sharp and accompanied with high levels of off odors. HPPP had the highest weight loss compared with other bags. MPPP12 bags maintained quality during storage and simulated shelf-life, in terms of higher scores for visual quality, firmness, crispness and taste as well as highest contents of chlorophyll, vitamin C and sugars. NPPP bags had the worst values for quality. At the end of storage and shelf-life, an increment in h* was observed in samples stored in MPPP6, MPPP12 and MPPP24 bags (more green color) in comparison with those in NPPP bags. ã 2014 Elsevier B.V. All rights reserved.
Keywords: Sugar snap peas Modified atmosphere packaging Microperforated polypropylene bag Cold storage Shelf-life Quality
1. Introduction Sugar snap peas (Pisum sativum L. var. saccharatum) are a new type of pea in Egypt, sown for export. They play an important role in human nutrition as a cheap source of protein, carbohydrates, vitamins, minerals and other nutrients. Edible-podded peas are harvested before physiological maturity is reached to retain their quality. Shortly after harvest, loss of sweetness and crispness, degreening and the development of mealiness may decrease quality. Kader (1992) stated that peas are a highly perishable immature commodity that can be cooled and stored at temperatures near 0 C to extend shelf-life. They have a very high respiration rate and are classified as a non-climacteric commodity. All types of peas can be stored for 1–2 weeks at 0 C and 95–98% RH (Suslow and Cantwell, 1998). The benefits of modified atmosphere packaging (MAP) are in extending shelf-life of products to meet market demand through reduction of metabolic activities and pathological deterioration. MAP vastly improves moisture retention by maintaining a higher
* Corresponding author. Tel.: +20 64 3481057. E-mail address: [email protected] (M.M.W. Elwan). http://dx.doi.org/10.1016/j.postharvbio.2014.10.006 0925-5214/ ã 2014 Elsevier B.V. All rights reserved.
RH around the fruit inside the sealed package, with an influence on preserving quality (Mangaraj et al., 2012). Passive modified atmosphere packaging is a technology that can be employed through the use of polymeric films with different numbers and dimensions of microperforations. Storability and shelf-life, as well as quality of fruit and vegetables, are affected by type, thickness and perforation of films used in MAP (Serrano et al., 2006; Simon et al., 2008; Jia et al., 2009; Simon and Gonzalez-Fandos, 2011; Selcuk and Erkan, 2014). Serrano et al. (2006) found that broccoli packaged in microperforated polypropylene film had prolonged storability up to 28 days with high quality attributes and health-promoting compounds. A micro-perforated polyethylene film with 2 holes extended shelf-life and reduced postharvest deterioration of broccoli florets stored at 4 and 20 C (Jia et al., 2009). Microperforated polypropylene films with 7 and 9 holes (90 mm) maintained strawberry quality during cold storage (Kartal et al., 2012). Packages with perforated areas of 1.57, 3.14 and 4.71 mm2 can be used to preserve strawberry quality for 10 days at 2 C (Sanz et al., 2002). Also, Almenar et al. (2007) reported that microperforated films with one and three perforations maintained the chemical, physical and sensory qualities of strawberries.
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Little information is available on passive modified atmosphere packaging of sugar snap peas. Sugar snap peas are exported from Egypt in highly perforated polypropylene traditional bags. This bag maintains visual quality for a maximum of 1–2 weeks. So, the peas are exported by air, which is very expensive. The main objective of the present investigation was to evaluate the influence of passive MAP by using perforated polypropylene (control), non-perforated polypropylene and three new microperforated polypropylene films with 6, 12 and 24 holes, on the changes in several parameters related to sugar snap pea quality during cold storage and shelf-life. A further aim of this work was to reduce the transportation costs by using sea freight instead of air through a prolonged storage period. 2. Materials and methods
A panel of five trained judges (members of Vegetable Handling Research Department, Horticulture Research Institute, Agricultural Research Center, Egypt) evaluated the visual quality of all pods from each bag at the end of each storage period and subsequent shelf-life. Visual appearance was scored on a 9 to 1 scale, where 9 = excellent and fresh appearance, 7 = good, 5 = fair (limited marketability), 3 = poor and 1 = unusable, according to Jimenez et al. (1998). Pod surface color was evaluated on 6 pods from each bag using a Hunter colorimeter (Hunter Instrument DP-9000, Japan) which measures L*, a*, b*, C* and h*. Higher positive hue values indicate green color. A color wheel subtends 360 , with red–purple traditionally placed at the far right (or at an angle of 0 ); yellow, bluish–green, and blue follow counterclockwise at 90 , 180 , and 270 , respectively as reported by McGuire (1992).
2.1. Plant materials and packaging treatments
2.4. Firmness, crispness, taste and off odors.
Sugar snap peas (P. sativum L. var. saccharatum cv. ‘super sugar snap’) was planted in winter of 2011–2012 (from 2nd October to 5th March) at the Experimental Research Farm, Faculty of Agriculture, Suez Canal University, Ismailia Governorate, Egypt, to produce the pods of sugar snap peas. Fresh pods were harvested by hand at the appropriate stage of maturity according to El-Seifi et al. (2014), on February 9, 2012 and transported to the laboratory of the Vegetable Handling Research Department, Horticulture Research Institute, ARC, Ministry of Agriculture, Egypt within 3 h. Pods were inspected and sound pods were held for 12 h at 0–2 C and 90–95% RH, then the tops and tail of the pods were cut, and the pods sorted and graded according to export criteria prior to packaging (Suslow and Cantwell, 1998). Fresh pods (250 g) were packed into five different types of polypropylene bags and sealed, with overall bags dimensions of 17 15 cm. Highly perforated bags (HPPP; obtained from El-Huda Company, Ismailia, Egypt), were 30 mm in thickness and with 1800 holes (1000 mm in diameter), commonly used for export in Egypt. The other bags (45 mm in thickness with 550 mm hole diameters) (obtained from ICOPACK Company, 6th of October, Giza, Egypt) were non-perforated bags (NPPP), micro-perforated bags with 6 holes (MPPP6), 12 holes (MPPP12) and 24 holes (MPPP24). Micro-holes were made in the bags using a 550 mm diameter cold needle (Watkins and Thompson, 1992). The bags were placed in 5 kg carton boxes (26 W 40 L 12 H) cm and stored at 0 1 C, with 90–95% RH for 21 days. After 7, 14 and 21 days of storage, 6 bags (a replicate) from each treatment were transferred to an evaluation room. To simulate commercial storage and marketing, 12 bags after 21 days at 0 C were kept sealed for 2 and 4 additional days (6 bags for each period) at 10 C and 80–85% RH, then transferred to the evaluation room for the same assessment.
Firmness was evaluated by pressing the pod (six pods from each bag) between the thumb. A scale of 5–1 was used; 5 (firm and turgid), 4 (firm), 3 (moderately firm), 2 (limp and shriveled) and 1 (more limp and shriveled). Panelists rated sugar snap peas for crispness by bending to break the pod (six pods from each bag), on a scale of 5–1; 5 (fully typical), 4 (moderately full), 3 (moderate), 2 (slight) and 1 (none) (El-Bassiouny, 2003). Panelists rated the taste of six pods from each bag on a scale of 5–1, where 5 (fully typical), 4 (moderately full), 3 (moderate), 2 (slight) and 1 (none) (Kader et al., 1973). Off odors of 6 bags from each treatment was evaluated on a scale of 5–1, where 5 (severe), 4 (moderately severe), 3 (moderate), 2 (slight) and 1 (none) (Kasmire et al., 1974). 2.5. Total chlorophyll content Total chlorophylls were extracted from fresh pods (0.5 g tissue from the center of the pods) by acetone (80%) and determined spectrophotometrically according to Lichenthaler and Wellburn (1983), and expressed as mg/100 g fresh weight. 2.6. Ascorbic acid content 10 g of pods tissue for each bag were ground thoroughly in a mortar with 40 ml of 4% oxalic acid solution. The mixture was poured into a 100 mL volumetric flask which was then filled with 4% oxalic acid solution and filtered through a filter paper (Whatman no. 1). Afterwards, 10 mL of supernatant were titrated to a permanent pink color by 0.1% 2,6-dichlorophenolindophenol. Ascorbic acid was calculated according to the titration volume of 2,6-dichlorophenolindophenol and expressed as mg/100 g fresh weight (Pearson, 1970).
2.2. O2 and CO2 concentrations 2.7. Total sugars and soluble solids contents The O2 and CO2 concentrations inside bag headspace during storage were analyzed using a DualTrak Model 902D gas analyzer (Quantek Instruments, USA) before opening. The headspace atmosphere within the 6 removal bags from each storage period was sampled using a syringe inserted through a septum. 2.3. Weight loss, visual quality, decay and color All bags were weighed at zero time and at the end of each storage period and at subsequent shelf-life, 6 bags were reweighed. The weight loss was determined and expressed as percent loss from initial weight.
5 g of fresh pods from each bag for each storage and subsequent shelf-life period were homogenized in 50 mL of 80% ethanol for 2 min and then refluxed for 30 min. The samples were centrifuged at 10,000 g for 30 min. The residue was again subjected to ethanol extraction. The extracts were combined and alcohol was removed by evaporation. An aliquot was taken and then made up to 50 mL with distilled water. Total sugars were measured with phenol–sulfuric acid reagents spectrophotometrically at 480 nm according to Dubois et al. (1956). Soluble solids content (SSC) were measured by hand refractometer according to AOAC (1996) and expressed as %.
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after 21 days of cold storage and 4 days at 10 C (p 0.001). Significant weight loss occurred during prolonged storage periods at 0 C and 10 C in HPPP bags. MPPP6, MPPP12, MPPP24 and NPPP bags had strongly reduced weight loss compared to the HPPP bags. During the storage and shelf-life periods (21 days at 0 C and 4 days at 10 C), the HPPP bag lost 4.38% of its weight while pea pods in MPPP6, MPPP12, MPPP24 and NPPP bags lost between 0.6% and 0.75% of their initial weight (Table 1). The appearance of the pods packed in HPPP were scored as good for marketability after 21 days of cold storage and also were at the limit of marketability after 2 days of shelf-life storage, which was lost when shelf-life was extended to 4 days. However, pods packed in NPPP bags lost their limit of marketability (poor) after 21 days of cold storage and were scored as unacceptable during shelf-life. The pods packed in MPPP12 bags kept their excellent and fresh appearance after 21 days of cold storage plus 2 days of shelf-life, then were scored as good for marketability when the shelf-life period was extended to 4 days. However, MPPP6 and MPPP24 bags maintained excellent and fresh appearance of pods during cold storage only, then scored at the limit for marketability at the end of shelf-life (Table 1). At the end of storage and shelf-life periods, no decay was observed for any packaging treatment (data not shown). External color of the pods was significantly affected by different gas concentrations within the packages. Pods packed in NPPP bags had the lowest h* values (more yellowing) in comparison to other packages after 21 days at cold storage plus 4 days at shelf-life storage. However, micro-perforated bags maintained the green color of pods even more than at harvest (Table 1).
2.8. Statistical analysis The experiments were organized in a completely randomized block design (CRBD) with a split plot arrangement, with six replications (bags), in which each replication was considered as a block. The bag treatments were randomly distributed in the main plots and the storage periods were randomly distributed in the sub-plots. Experimental data were analyzed by analysis of variance (ANOVA) using CoStat version 6.303 1998–2004 CoHort software, 798 Lighthouse Ave, PMP 320, Monterey, CA 93940, USA. Duncan’s test was used to compare means at the 5% significance level. Standard error (SE) of means were calculated for presentation in figures using SigmaPlot version 10.0 (Systat Software Inc., Hounslow, UK) 3. Results 3.1. O2 and Co2 concentrations During storage, headspace O2 concentration significantly decreased in all packages. The O2 concentration decreased sharply from 16.8% to 1.23% in NPPP bags during the first 7 days of storage, then increased up to 5.17% at the end of storage and shelf-life. However, O2 concentrations in MPPP6, MPPP12 and MPPP24 bags decreased to 11.97, 14.12 and 14.77%, respectively, while the HPPP bag maintained the highest O2 concentration (15.58%) at the end of storage and shelf-life. The CO2 concentration increased quickly for NPPP bags in the first week from 0.1% to 52.17% (the highest CO2 concentration), then declined by the end of storage plus shelf-life to 27.7%. The CO2 concentrations inside MPPP6, MPPP12 and MPPP24 bags were about 4%, 1.5% and 0.7% after 7 days of cold storage and by the end of storage and shelf-life the concentrations were slightly increased to 9.8%, 3.9% and 1.8%, respectively. However, HPPP bags showed no change in CO2 concentration during all storage and shelf-life periods (Fig. 1a and b).
3.3. Firmness, crispness, taste and off odors Firmness, crispness, taste and off odors were significantly affected by MAP, storage time and their interaction after 21 days of cold storage and 4 days at 10 C (p 0.001). Pods packed in HPPP kept their firmness, crispiness and taste (firm, turgid and fully typical) only up to 14 days of cold storage and after 21 days of cold storage plus 4 days shelf-life, the scores values ranged between 2.33 and 2.67 (limp, shriveled and slight) which was unacceptable for marketing. However, pods in MPPP12 bags were firm, turgid and fully typical (score; 5) during the cold storage period plus
3.2. Weight loss, visual quality and color There were significant effects of MAP application, storage time and their interaction on weight loss, visual appearance and color
a
207
b
18
o
(0 C)
o
(10 C)
50
(0oC)
(10oC)
CO 2 concentration (%)
O2 concentration (%)
16
14
12
HPPP NPPP MPPP6 MPPP12 MPPP24
6
4
40 HPPP NPPP MPPP6 MPPP12 MPPP24
30 10
2
0 0
0
7
14 21 21+2 Storage period (days)
21+4
0
7
14 21 21+2 Storage period (days)
21+4
Fig. 1. Changes O2 (a) and CO2 (b) concentrations inside MAP during cold storage (0 C) and simulating shelf life at 10 C. Vertical lines represent the standard deviation. Samples size = 6.
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Table 1 Weight loss, visual appearance, h* values of cv. super sugar snap peas after cold storage at 0 C and simulating shelf life at 10 C. Package treatments
Cold storage plus shelf life periods (days)
At harvest
HPPP 21 21
NPPP 21 21
MPPP6 21 21
MPPP12 21 21
MPPP24 21 21
0.0 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4
Significance Package treatments (P) Storage + shelf life (S) PS
Weight loss (%)
Visual appearance (index number)
h*
0.00 1.88d 1.94d 3.60c 3.79b 4.38a 0.31lm 0.41ijkl 0.59fgh 0.61fg 0.66ef 0.26m 0.33klm 0.43ijk 0.50ghi 0.60fg 0.26m 0.36klm 0.48hij 0.56fgh 0.66ef 0.31lm 0.38 jkl 0.51ghi 0.60fg 0.75e
9.00 9.00a 9.00a 7.00b 5.00c 3.00d 9.00a 7.00b 3.00d 1.00e 1.00e 9.00a 9.00a 9.00a 7.00b 5.00c 9.00a 9.00a 9.00a 9.00a 7.00b 9.00a 9.00a 9.00a 7.00b 5.00c
119.05 119.09i 120.76a 120.50ab 120.39abc 120.25a–f 119.63f–i 119.85c–h 117.55j 117.50j 114.15k 119.69e–h 120.29a–e 120.13a–f 120.25a–f 119.93b–h 119.74d–h 119.81c–h 120.20a–f 119.91b–h 120.13a–f 119.34hi 119.48ghi 120.07b–g 120.02b–g 120.35a–d
*** *** ***
*** *** ***
*** *** ***
The values within a column with different letters are significantly different at p 0.001% according to the Duncan’s multiple range test.
2 days as shelf-life, then scored as firm and moderately full (score; around 4) when the shelf-life period was extended to 4 days. At the end of cold storage (21 days) at 0 C without shelf-life, the pods packed in NPPP bags were unacceptable for marketing (scores; <3) and after the shelf-life period (4 days) the pods were destroyed and wasted. This package showed an increase in off odors with prolongation of cold storage and shelf-life periods, reaching the severe score (4.67), however no off-odors were detected in the other bags (Table 2). 3.4. Chlorophyll content Generally, a degradation in chlorophyll was observed in all packaging treatments. Samples stored in NPPP bags had the lowest chlorophyll values at the start of the storage period (7 days) compared with the other bags. At the end of cold storage and shelflife, MPPP12 bags maintained the highest chlorophyll levels, followed by MPPP24 bags (Table 2). 3.5. Vitamin C Vitamin C content of sugar snap peas was increased (up to 78 mg/100 g) after 7 days of cold storage comped with values at harvest (71.37 mg/100 g) in all samples stored in all bags, except the HPPP bag. At the end of cold storage (21 days), a reduction in the ascorbic acid was observed; this reduction was higher in NPPP bags (approx. 58%). At the end of cold storage and shelf-life, the highest content of ascorbic acid (54 mg/100 g) was measured in samples stored in MPPP12 bags. However, the lowest vitamin C (23.13 mg/100 g) was measured in NPPP (Table 2).
3.6. Total sugar and soluble solids contents There were significant effects of MAP application, storage time and their interaction on total soluble sugars content and soluble solids content (SSC) after 21 days of cold storage and 4 days at 10 C (p 0.001). A negligible changes (69–71.55 mg/g FW) in sugar contents were detected after initial cold storage (7 days) in samples stored in MPPP6, MPPP12 and MPPP24 in comparison with at harvest (70.51 mg/g FW), however, in NPPP samples, the sugar contents were reduced by 10%. At the end of cold storage and shelflife, samples stored in MPPP12 had the highest total sugar content (61.09 mg/g) followed by MPPP24 and MPPP6 (58.82–59.07 mg/g FW), then HPPP (57.23 mg/g FW). However, a sharp reduction (40.85 mg/g FW) in total sugars was observed in samples stored in NPPP bags (Table 2). At the end of cold storage and shelf-life at 10 C, SSC significantly improved from 13.5% to around 17% in pods bagged in MPPP6, MPPP12 and MPPP24, followed by HPPP bags (15.5%). However, a sharp decline in SSC (10.58%) was observed in pods stored in NPPP bags at the end of cold storage and shelf-life periods (Table 2). 4. Discussion Peas are a highly perishable product and shelf-life and visual quality greatly depend on storage conditions such as temperature and atmosphere composition (Kader, 1992; Pariasca et al., 2001). Our results showed that cooling (0 C) and/or modified atmospheres created by MPPP12 (14.12% O2 and 3.9% CO2) greatly extended the cold storage and shelf-life of snap peas, in comparison with HPPP and NPPP bags. The atmosphere
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Table 2 Off odor, firmness, crispness, taste, total chlorophyll, vitamin C and total sugars of cv. super sugar snap peas after cold storage at 0 C and simulating shelf life at 10 C. Index number Package treatments
Cold storage plus shelf life periods (days)
At harvest
HPPP 21 21
NPPP 21 21
MPPP6 21 21
MPPP12 21 21
MPPP24 21 21 Significance Package treatments (P) Storage + shelf life (S) PS
0.0 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4 7 14 21 +2 +4
mg/100 g FW
mg/g FW
Off odor
Firmness
Crispness
Taste
Total chlorophyll
Vitamin C
SSC (%)
Total sugars
1.00 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 2.00d 3.00c 4.00b 4.67a 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e 1.00e
5.00 5.00a 5.00a 4.00b 3.17c 2.33d 5.00a 4.00b 3.00c 2.00e 1.00f 5.00a 5.00a 5.00a 4.00b 3.17c 5.00a 5.00a 5.00a 5.00a 4.00b 5.00a 5.00a 5.00a 4.00b 3.83b
5.00 5.00a 5.00a 4.00c 3.00e 2.67f 5.00a 4.00c 2.67f 1.00g 1.00g 5.00a 5.00a 5.00a 4.33b 3.67d 5.00a 5.00a 5.00a 5.00a 4.67a 5.00a 5.00a 5.00a 4.33b 3.67d
5.00 5.00a 5.00a 4.00bc 3.50d 2.50e 5.00a 4.00bc 2.50e 1.00f 1.00f 5.00a 5.00a 4.33b 4.00bc 3.83c 5.00a 5.00a 5.00a 4.00bc 4.00bc 5.00a 5.00a 4.67a 4.00bc 3.5d
12.11 11.70a 10.67bcd 10.09d–g 8.86hi 8.81hi 9.445gh 8.10i 7.05j 6.91j 7.09j 11.178abc 10.30d–g 8.84hi 10.36c–f 9.77efg 11.35ab 10.42c–f 10.05d–g 10.10d–g 10.53b–f 11.76a 10.66b–e 9.74fg 10.45c–f 10.09d–g
71.37 70.76ef 70.53f 64.21gh 52.53jk 51.60kl 78.13a 62.78gh 33.04m 31.98m 23.13n 75.07bc 74.23bcd 71.17ef 62.44h 49.66l 75.74b 72.30def 64.91g 57.19i 54.50j 75.68b 72.96cde 62.18h 53.19jk 52.87jk
12.62 13.50f 15.17cd 15.72bc 15.48bc 15.52bc 13.83ef 13.33f 11.72g 11.17gh 10.58h 13.87ef 14.83cd 16.60a 16.72a 16.75a 14.5de 15.42c 16.80a 16.55a 17.00a 14.83cd 15.25cd 16.33ab 16.92a 17.03a
70.51 67.65cd 64.73ef 60.96i–l 60.51jkl 57.23m 63.31fgh 60.97i–l 57.27m 44.71n 40.85o 69.00bc 65.91de 62.20ghij 61.55ghij 58.82lm 71.55a 67.60cd 63.77efg 63.77efg 61.10h–k 70.32ab 67.02cd 63.23f–i 62.78fg–j 59.07klm
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
The values within a column with different letters are significantly different at p 0.001% according to the Duncan’s multiple range test.
composition within the packages depended on the number, diameter of the holes and the thickness of the film used. The results indicated an increment of CO2 (except HPPP; unchanged) and a reduction in O2 during prolonged storage time, depending on type of packaging. This result has a number of similarities with results of Kartal et al. (2012) who found that CO2 accumulation and O2 depletion were dependent on perforation surface. In our investigation, the reduction of O2 and the increase of CO2 were within an acceptable range for pod preservation, since good freshness, excellent crispness (fully typical) and no off odors was detected in MPPP12 bags. The favorable effects of MPPP6, MPPP12 and MPPP24 bags regarding crispness may be due to maintaining cell wall strength, cell-cell adhesion, turgidity of cells with retardation of senescence processes and lower respiration rates influenced by gas composition inside the packaging (Escalona et al., 2007b). Similarly El-Bassiouny (2003) with green beans, Escalona et al. (2004) with fennel and Escalona et al. (2007a) with kohlrabi found that micro-perforated films resulted in high firmness values. NPPP bags (45 mm) had the highest CO2 (27.7%) and the lowest O2 (5.17%) levels compared with other bags, and this may be due to high respiration rates of the tested sugar snap peas. This result was similar to results of Lucera et al. (2011) who reported that it is possible that high barrier films enable faster CO2 accumulation and O2 consumption in the package. Hansen et al. (2001) reported that levels of CO2 over 20% induced anaerobic metabolism with generation of off odors mainly due to acetaldehyde of ethanol. Also, Almenar et al. (2007) concluded that low O2 concentrations in non-perforated packages cause breakdown of tissue and off flavor development. Significant differences were observed among the five different packages. MPPP12 (45 mm and 12 holes with 550 mm) preserved the sugar snap pea pods with good visual appearance, firmness,
fully typical for crispness and moderately full for taste (acceptable) at the end of 21 days cold storage and 4 days stimulating shelf conditions. These results are in accordance with the results of Sakaldas et al. (2010) and Fernandez-Leon et al. (2013a,b); Fernandez-Leon et al. (2013a,b) who found that controlled atmosphere and low-density polyethylene based modified atmosphere packaging had the best visual quality for dill and broccoli, respectively. However, HPPP (30 mm and 1800 holes with 1000 mm) kept the pods with good, firm and moderately full visual quality, firmness, crispiness and taste (acceptable) at the end of cold storage (21 days) only, and when packages were transferred to shelf conditions up to 4 days at 10 C, the pods appeared unacceptable for marketing (limp and shriveled for firmness and slight for crispness). Tissue yellowing is an important factor in quality deterioration in stored green vegetables such as sugar snap peas. In our study, the gas composition within the investigated packages significantly affected the external pod color. Micro-perforated (approx. 14% O2 and 4% CO2) packages kept the green color of the pods, giving product acceptability for commercial purposes. On the other hand, h* decreased at significant levels in samples stored in NPPP bags (5.17% O2 and 27.7% CO2), which is a good indicator for decreasing green color. As reported before in snow peas, when h* values decrease, a reduction in green color and increment in yellow color occurs (Pariasca et al., 2001). There is a relationship between color parameters and chlorophyll content, where our data showed that pods stored in MPPP12 bags retained the highest chlorophyll content at the end of storage and shelf-life periods. Also, the faster loss in chlorophyll content was recorded in samples stored in NPPP bags, and this reduction may be due to chlorophyll degradation under the influence of high levels of CO2. Our results are in agreement with Sakaldas et al. (2010) who found that
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modified atmosphere packaging retarded the reduction of chlorophyll content in dill. Also, these results were in accordance with Nath et al. (2011) who found that micro-perforated polypropylene packages retained the highest broccoli chlorophyll content.
loss more than HPPP bags and prevented off odors better than NPPP bags.
In our study, a noticeable weight loss was observed in the HPPP bag during the entire storage and shelf-life periods. However, the weight loss was significantly reduced in MPPP6,MPPP12, MPPP24 and NPPP bags in comparison with the HPPP bag. This could be due to the effect of lower number of microholes as well as smaller microhole diameter on increasing water vapor pressure around the material, and in turn, reduction of the transpiration rate. Also, this effect may be in part due to the thickness, whereas the thickness of MPPP6, MPPP12, MPPP24 and NPPP bags was 45 mm and the HPPP bag 30 mm, which would have increased the transpiration rate.
Association of Official Analytical Chemists, 1996. Official Methods of Analysis. Association of Official Analytical Chemists, Washington, D.C. Albuquerque, B., Lidon, F.C., Barreiro, M.G., 2005. A case study of tendral winter melons (Cucumis melo L.) post harvest senescence. Gen. Appl. Plant Physiol. 31, 157–169. Almenar, E., Del-Valle, V., Hernandez-Munoz, P., Lagaron, J.M., Catala, R., Gavara, R., 2007. Equilibrium modified atmosphere packaging of wild strawberries. J. Sci. Food Agric. 87, 1931–1939. Bodelon, O.G., Sanchez-Ballesta, Blanch M., Escribano, M.T., Merodio, M.I., 2010. The effects of high CO2 levels on anthocyanin composition, antioxidant activity and soluble sugar content of strawberries stored at low non-freezing temperature. Food Chem. 122, 673–678. Del-Valle, V., Hernandez-Munoz, P., Catala, R., Gavara, R., 2009. Optimization of an equilibrium modified atmosphere packaging (EMAP) for minimally processed mandarin segments. J. Food Eng. 91, 474–481. Dubois, M.K.A., Hamilton, J.K., Rebers, P.A., Smith, F., 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28, 350–356. El-Bassiouny, R.E.I., 2003. Modified atmosphere polyethylene packages maintain the quality of snap bean pods during storage. J. Agric. Sci. Mansoura Univ. 28, 3869–3888. El-Seifi, S.K., Hassan, M.A., Ibrahim, Rawia E., Elwan, M.W.M., Nasef, I.N., 2014. Effect of maturity stage on physical and chemical characteristics and determination of harvest time of sugar snap pea pods. J. Plant Prod. Mansoura Univ. 2, 305–314. Escalona, V.H., Aguayo, E., Artes, F., 2007a. Extending the shelf life of kohlrabi stems by modified atmosphere packaging. J. Food Sci. 72, 308–313. Escalona, V.H., Aguayo, E., Artes, F., 2007b. Modified atmosphere packaging improved quality of kohlrabi stems. Food Sci. Technol. 40, 397–403. Escalona, V.H., Aguayo, E., Gomez, P., Artes, F., 2004. Modified atmosphere packaging inhibits browning in fennel. Food Sci. Technol. 37, 115–121. Fernandez-Leon, M.F., Fernandez-Leon, A.M., Lozano, M., Ayuso, M.C., GonzalezGomez, D., 2013a. Altered commercial controlled atmosphere storage conditions for ‘Parhenon’ broccoli plants (Brassica oleracea L. var. italica). Influence on the outer quality parameters and on the health-promoting compounds. Food Sci. Technol. 50, 665–672. Fernandez-Leon, M.F., Fernandez-Leon, A.M., Lozano, M., Ayuso, M.C., GonzalezGomez, D., 2013b. Different postharvest strategies to preserve broccoli quality during storage and shelf life: controlled atmosphere and 1-MCP. Food Chem. 138, 564–573. Hansen, M.E., Sorensen, H., Cantwell, M., 2001. Changes in acetaldehyde, ethanol and amino acid concentrations in broccoli florets during air and controlled atmosphere storage. Postharvest Biol. Technol. 22, 227–237. Jacob, R.A., Sotoudeh, G., 2002. Vitamin C function and status in chronic disease. Nutr. Clin. Care 5, 66–74. Jia, C.G., Xu, C.J., Wei, J., Yuan, J., Yuan, G.F., Wang, B.L., Wang, Q.M., 2009. Effect of modified atmosphere packaging on visual quality and glucosinolates of broccoli florets. Food Chem. 114, 28–37. Jimenez, M., Trijo, E., Cantewell, M., 1998. Postharvest Quality Changes in Green Bean. Research Report. U.C. Davis Cooperative Extension Service, pp. 9. Kader, A.A., 1992. Postharvest biology and technology: an overview and modified atmosphere during transport and storage. In: Kader, A.A. (Ed.), Postharvest Technology of Horticultural Crops. University of California, Publication 3311, USA pp. 15–17, 85–92. Kader, A.A., Lipton, W.J., Morris, L.L., 1973. Systems for scoring quality of harvested lettuce. HortScience 8, 408–409. Kartal, S., Aday, M.S., Caner, C., 2012. Use of microperforated films and oxygen scavengers to maintain storage stability of fresh strawberries. Postharvest Biol. Technol. 71, 32–40. Kasmire, R.F., Kader, A.A., Klaustermeyer, J.A., 1974. Influence of aeration rate and atmospheric composition during simulated transit on visual quality and off odor production by broccoli. HortScience 9, 228–229. Kinyuru, J.N., Kahenya, K.P., Muchui, M., Mungai, H., 2011. Influence of post-harvest handling on the quality of snap bean (Phaseolus vulgaris L.). J. Agric. Food Technol. 1, 43–46. Lichenthaler, H.K., Wellburn, W.R., 1983. Determination of total carotenoids and chlorophylls a and b of leaf extracts in different solvents. Biochem. Soc. Trans. 11, 591–592. Lucera, A., Conte, A., Del Nobile, M.A., 2011. Shelf life of fresh-cut green beans as affected by packaging systems. Int. J. Food Sci. Technol. 46, 2351–2357. McGuire, R.G., 1992. Reporting of objective colour measurements. HortScience 27, 1254–1255. Mangaraj, S., Goswami, T.K., Giri, S.K., Tripathi, M.K., 2012. Permselective MA packaging of litchi (cv: Shahi) for preserving quality and extension of shelf-life. Postharvest Biol. Technol. 71, 1–12. Mapson, C.W., 1970. 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Several studies have shown that the consumption of foods rich in vitamin C are associated with a decreased risk of several chronic diseases, including cardiovascular disease and cancer (Jacob and Sotoudeh, 2002). Generally in our investigation, vitamin C was reduced by prolongation of storage and shelf-life periods. This reduction may be due to oxidizing enzymes, e.g., ascorbic acid oxidase that reduces the ascorbic acid of the fruit and vegetables, as reported by Mapson (1970) and converts it to dehydroascorbic acid (Albuquerque et al., 2005). However higher ascorbic acid preservation (approx. 70–76%) associated with HPPP, MPPP6, MPPP12 and MPPP24 may be related to the limitation of atmospheric oxygen for oxidation. Similar trends were reported by Pariasca et al. (2001) for snow peas, Kinyuru et al. (2011) for snap beans and Fernandez-Leon et al. (2013a,b); Fernandez-Leon et al. (2013a,b) for broccoli. SSC increased in samples stored in MPPP followed by HPPP packages with the prolongation of storage. Similar results were reported by Fernandez-Leon et al. (2013b) who indicated that SSC in broccoli increased with the prolongation of storage. Our findings seem to be in accordance with Kartal et al. (2012), who showed that perforated films resulted in higher SSC contents than nonperforated polypropylene with strawberries. It is possible that low SSC values of NPPP films are due to the effect of less oxygen and more carbon dioxide in the packages, reflecting a high respiration rate (Del-Valle et al., 2009). Another possible explanation is that high CO2 concentrations inside NPPP packages triggered hydrolysis and glycolysis reactions, resulting in consumption of sugars as reported by Bodelon et al. (2010). In the same direction, data presented herein showed that pods stored in MPPP12 bag maintained the highest values of total sugar contents. Our findings were not due to low weight loss, because the lower weight loss was also detected in NPPP bags, but this results may be due to low respiration rates which would retard loss of sugar. Also, this small reduction in total sugars in desirable bags (MPPP) may be due to normal senescence processes which continue during the storage period, resulting in a reduction of sugar contents as reported before in snow peas (Pariasca et al., 2001). However, the sharp reduction in measured total sugars of samples stored in NPPP bags may be due to higher respiration (higher CO2%) rates associated with consumption of sugars. In conclusion, by controlling the number of holes and their diameter as well as the thickness of polypropylene films, it could be possible to extend cold storage of sugar snap peas for 3 weeks and preserve their good appearance during shelf-life conditions for 4 days. Through the equilibrium of O2 and CO2 (14% O2 and 4% CO2) in MPPP12 bags, the visual quality, color, firmness, crispness, taste, SSC, vitamin C and sugars contents maintained high values in comparison to NPPP and HPPP bags. MPPP bags reduced the weight
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