Meysam Mohammadi; Mehdi Saidi; Orang Khademi
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 ...
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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.
Materials 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 Discussion: 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.
Orang Khademi; Younes Nemati
Abstract
Introduction: There are two types of Japanese persimmon (Diospyros kaki Thunb.), astringent and non-astringent, based on the degree of astringent taste at maturity state. Fruits of either type are strongly astringent when small and immature, but non-astringent type loses its astringency during development ...
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Introduction: There are two types of Japanese persimmon (Diospyros kaki Thunb.), astringent and non-astringent, based on the degree of astringent taste at maturity state. Fruits of either type are strongly astringent when small and immature, but non-astringent type loses its astringency during development on the tree, still with firm flesh. However, the astringent type keeps its astringency and is inedible even when fully colored. It loses its astringency when becomes over-ripe with extremely soft flesh. At this stage, the fruits are usually over ripe with poor quality. Astringency in persimmon is caused by soluble tannins present in the fruit flesh. One mechanism useful in artificial removal of astringency from persimmon fruit is condensation or polymerization of soluble tannins into insoluble non-astringent forms, by acetaldehyde, which is being produced in the fruit flesh during different treatments. Acetaldehyde accumulates in the fruit flesh during its exposure to ethanol vapor or high level of carbon dioxide (CO2) gas, Hence, constant temperature and short duration (CTSD) is the preferred method of CO2 treatment used to remove astringency of persimmon fruit. It involves holding the fruits in ≥95% carbon dioxide atmosphere for a short duration at constant temperature of 20-30°C then transferring to normal atmosphere. However using CO2 treatment as gas form is expensive and needs special equipment. However, solid CO2 (dry ice) is easily available in Iran with low price. It release CO2 gas and can be used for removing astringency in persimmon fruit. The response of persimmon to de-astringent treatment depends on the cultivar. In this study two persimmon cultivars namely: ”Karaj” and ”Japanese” were harvested at maturity (full coloring) stage and treated with dry ice and ethanol vapor to remove astringency and the quality of treated fruits were evaluated.Materials and methods: Astringent persimmon fruits cvs ‘Karaj’ and ‘Japanese’ were harvested at maturity stage and transported immediately to the Department of Horticulture Science, University of Shahed and treated with either ethanol or dry ice. Both ethanol and dry ice treatmenttreatments were applied in low-density polyethylene bags with 0.05 mm thickness and polyethylene container with 3 mm thickness. In the polyethylene container, dry ice was applied at amounts of 3, 5 and 7% per kilograms of fruit and in the polyethylene bags dry ice was applied at amount of 0.16, 0.25 and 0.33 per kilogerams of fruits. For ethanol treatment, in both polyethylene bag and polyethylene container, 10 ml of 36% ethanol per kilogram of fruit was sprayed. Thereafter, bags and containers were sealed completely and kept for 48 hours at 25°C and 80% RH. After removing from the closed bags and containers, fruits were held in air at 25°C, 80% RH for completing astringency removing. After astringency removal treatmenttreatments, soluble tannin contents, astringent taste degree, fruit firmness, total soluble solid and ascorbic acid content were measured. The content of soluble tannin was determined by Folin-Denis method and the degree of astringency was determined by panel test. The experiments were conducted in a completely randomized design (CRD) and analysis of variance (ANOVA) was performed and the means were compared using LSD Test.Results and discussion: After performing the astringency removal treatment, fruits containing less than 1000 ppm of soluble tannin on a fresh weight basis showed no astringency. Results presented here showed that, dry ice treatment, especially at higher concentrations such as 7% in both cultivars, causes removal of astringency and decreases soluble tannin contents below the threshold of 1000 ppm, but ethanol treatment was effective only in Karaj persimmon for the removal of astringency. Similarly, it was indicated that CO2 treatment removed the astringency more easily in some Chinese cultivars than the ethanol treatment. The response of persimmon cv. Karaj was similar to a leading cultivar Hiratanenashi in Japan, for astringency removal by both CO2 and ethanol treatments, while, according to this results, Japanese cultivar had not shown suitable response to ethanol, while it successfully responded to dry ice treatment.Treatments to remove astringency of persimmon fruit often cause fruit softening. Astringency removal treatment induced ethylene production in persimmon which causes to the fruits softening. In this study, the firmness of both cultivars decreased significantly after treatments, however, the average of flesh firmness was significantly higher after dry ice than after ethanol treatments.Total soluble solid contents under the astringency removal treatments in both cultivars reduced significantly. This reduction is due to the removing of soluble tannins responsible for fruit astringency, since they are included in SSC measurements when not polymerized. Moreover, the results showed that ascorbic acid content is not affected by astringency removal treatments.Conclusions: The results presented here showed that removing astringency from persimmon cvs. Karaj and Japanese were achieved by postharvest application of dry ice in the poly ethylene container. Results also showed that dry ice was more effective than ethanol in astringency removal and retained higher quality of fruit. Dry ice is available treatment in Iran and it can be commercially used for removing astringency of Iranian persimmon.
