Effect of Cellophane and Chitosan Coatings on Qualitative and Biochemical Characteristics of Sweet Pepper, Cultivar “California wonder” during Storage

Abstract

Introduction Bell pepper (Capsicum annuum L.) from Solanaceae family is one of the most important vegetables which are fruit pods on the capsicum plant grown for their sweet fruits and delicate peppery flavor they extend to the recipes. Sweet pepper contains an impressive list of plant nutrients that found to have disease preventing and health promoting properties. Unlike in other fellow chili peppers, it has very less calories and fats. 100 g provides just 31 calories. Because of their versatility, low calories, intense flavor and high concentration of vitamins, sweet peppers are a great snack raw and an easy addition to many different recipes. In recent years extending shelf-life of this perishable vegetable has been accomplished (Banaras et al., 2005). The losses in vegetable quality and quantity between harvest and consumption affect the crop productivity. It is estimated that the magnitude of the postharvest losses of fresh horticultural crops is from 5 to 25% in developed countries and of 20 to 50% in developing countries. Fresh peppers are often eaten raw and supplied pre-cut to manufacturers as ready-to-use ingredients. However, the main problems limiting their shelf life occur by shriveling, decay development on the cut surface, as well as degreening of the vegetable among different degraded quality characteristics (Sakaldas and Kaynas, 2010). Those problems are correlated to an undesirable loss of water during metabolism or diffusion through the skin and respiration. Temperature management is the most effective tool for extending the shelf life of fresh horticultural commodities. Nowadays, to reduce high losses and keeping product’s quality, in addition to lowering temperature, coating and packing must be noticed. Therefore, in this study, dipping in chitosan solution and coatings by edible Chitosan was assayed to improve quality of sweet peppers storability during cold storage. Material and Methods Plant material and sample preparation: Green peppers obtained from a Research farm, College of Agriculture, Ilam University, Ilam, Iran were used in the present study. The fruits were sanitized with hyperchlorinated water (1 mL/L) and rinsed with tap water. Peppers were divided in random into different group for chitosan treatments. Treatments and storage condition: The green peppers were dipped for 2 min into a solution either 0% (control) or 1% (w/v) chitosan (Chitosan, 80-95% deacetylation degree, medium molecular weight). The coating solution was prepared by dispersing 0 and 10 g of chitosan powder into 1L of distilled water containing 1% (v/v) glacial acetic acid (Kyu Kyu Win et al., 2007) and final pH of the solution adjusted to pH 5.0. After being air dried for 2 hrs. at room Temperature, ten similar sizes fruits were placed in each plastic crate, tightly closed by cellophane films and stored at 10°C, 85-90% relative humidity to be later assessed for further analyses intended for 14 and 28 days. The control samples of ten untreated fruits per crate were kept unsealed under similar environmental conditions of temperature and relative humidity separately. The current study carried out as a factorial assay on the basis of a RCBD with three replications during 2013-2014 at Ilam University. The main factor was included of four treatments (control, Chitosan coating, Cellophane sealing and Chitosan coating + Cellophane sealing) and the sub factor was included of storage period duration (14 and 28 days). Data were subjected to ANOVA using SAS software version 9.2. Verification of significant differences was done using Duncan's Test at 5% probability level. Results and discussions Results showed that fruits quality declines with long storage, but treatments with Cellophane and Chitosan decreased weight loss and kept firmness, TSS, titratable acidity, sugar/acid ratio, ascorbic acid, antioxidant activity, total phenol, and catalase and peroxidase enzymes better than control. Furthermore, for most of the traits no significant difference was observed between treatments, although cellophane coating recorded more fungal infection and lower marketability. Shelf life enhancement by Chitosan has been already reported on carrot, orange and Japanese Medlar (Rashidi et al., 2009, Ahmad et al., 1989 & Ding et al., 2002) through its antimicrobial activity (Xing et al., 2011) and suppressing respiration by blocking stomata. It has been reported that both edible and nonedible coverage (such as chitosan and cellophane) of fruits can provide a modified atmosphere surround them which results in decreasing the rate of their maturity and senesces. Taking overall quality into consideration, the best treatment was joint application of cellophane and chitosan. That treatment appears to be an effective method for improving the postharvest quality of peppers which could more effectively preserved quality and biochemical characteristics. These fruits remained hydrated, green and had good visual appearance after storage. The low rate of respiration of these fruits may also account for the retention of pepper quality.