بررسی اثر پوشش‌های نانوکامپوزیت کیتوسان-رس، واکس و روغن زیتون روی برخی ویژگی‌های کیفی لیموشیرین در طی انبارمانی عمر قفسهای

مرکبات به ‌عنوان یک محصول عمده و قابل دسترس در تمام جهان و میوه‌ای محبوب در رژیم غذایی است. وارد آمدن آسیب به پوست میوه ،کاهش رطوبت و چروکیدگی پس از برداشت همگی سبب کاهش بازار پسندی این محصول می‌ گردند. استفاده از پوشش‌های خوراکی یکی از موثرترین راه‌ها در حفظ کیفیت میوه‌ها است. در این پژوهش کیفیت میوه لیموشیرین بر اساس آزمون فاکتوریل در قالب طرح کاملا تصادفی با پوشش خوراکی نانوکامپوزیت کیتوسانرس در سه سطح، روغن زیتون و واکس کارنوبا در مقایسه با نمونه بدون پوشش طی 12 روز انبارمانی مورد ارزیابی قرار گرفت. در طی دوره انبارمانی ویژگی‌های شیمیایی، ph، اسیدیته ، tss آب میوه، درصد کاهش وزن، ویتامین سی و ویژگی‌های مکانیکی، ضریب کرویت، نیروی برش پوست، نیروی شکست و نیروی کشش پوست میوه اندازه‌گیری شدند. نتایج نشان دهنده وجود تفاوت معنی‌دار در سطح 1% و 5% بین پوشش‌های مختلف در حداکثر نیروی شکست، درصد کاهش وزن و ph بود. در ضمن تاثیر زمان‌های مختلف انبارمانی بر میزان مواد جامد محلول در آب، ph و حداکثر نیروی شکست نیز معنی‌دار بود. پوشش کیتوسانرس 5 % کمترین میزان درصد کاهش وزن را داشت و بیشترین میزان درصد کاهش وزن به ترتیب برای پوشش شاهد و روغن زیتون 12.3 و 10.23 درصد بود. به طور کلی نتایج نشان داد میوه‌های پوشش داده در حفظ خواص کیفی و مکانیکی نسبت به نمونه‌های بدون پوشش عملکرد بهتری داشتند و در بین پوشش‌های مصرف شده پوشش نانو کامپوزیت کیتوسانرس 5 % موفقیت بالاتری نسبت به سایر پوشش‌ها داشت.

The effect of chitosan-clay Nano composite, wax coatings and olive oilon some quality properties of sweet lemon during shelf life storage

Introduction Citrus are one of the major agricultural production available in the world and it is one of the popular fruits in the diet. The most wellknown varieties of citrus fruits include oranges, lemons, grapefruits and tangerines. Cultivation of sweet lemon requires specific climate situation that it is found in many region of Iran. However, the high quality ones are in Jahrom, Ghsre Shirin, Dezfool, Jiroft and the Sorth of Iran. Two major limitation of longterm storage for citrus fruits are decay caused by pathogens, especially fungi, skin fruit damage and water loss, which can cause wrinkles and reduce product marketability and consumer acceptability. Edible coatings are one of the most effective methods to maintaining the fruit quality. Today edible coatings can preserve citrus quality and provide attractive approach to satisfactory performance. Chitosan is used for film or edible coatings to extend the shelf life of foods such as fruits, meat and fish and foods. The results of several studies indicate the effective role of chitosan in controlling fruit during storage. Wax in the fruit is used to prevent moisture loss and wrinkle of the fruit and also to maintain the appearance of the product and its marketability. So, the final goal of this study is investigate the effect of edible coatings (chitosanclay Nano composite, Wax coatings and olive oil) on some quality attributes of sweet lemon during shelf life storage.Materials and Methods Sweet lemon’s fruits (216 N.) were harvested randomly from a citrus orchard in Dezfool, Iran. The samples immediately sent into the laboratory for storage after necessary treatments. All fruits were disinfected by immersion in 4% chlorox for 3 minutes and then dried. Chitosan with low molecular weight (43 KD) was bought from Sigma Aldrich Company. Clay was purchased from Sefid Sang Aligoodarz Company in Iran and wax coating was provided from Pooshesh Hayat sabz company in Iran. The chitosanclay coating was prepared by dissolving a mixture of chitosan (3w/v% to solution), clay (5, 10 and 15% wt to chitosan) and glycerol (10v/w% to chitosan) and tween 80(5% v/w to chitosan) in acid lactic solution (2%). Nano structure of chitosanclay nanocomposite was approved by XRD analysis. The chemical parameters of fruit juice such as TSS (%), pH(%) and TA (%) of lemon juice were measured. TSS was determined by digital refractometer (model MA882, made in Japan). pH was measured by pHmeter ( portable p755 model) and TA was determined by AOAC standard method. The experiment was performed at three levels of chitosanclay nanocomposite, olive oil, Carnoba wax and uncoated samples during 12 days shelf life storage. The experimental design was factorial based on completely randomized design with three replications. Limon samples were maintained at ambient temperature of 25 ℃ and relative humidity of 8085%. Chemical characteristics (pH, citric acid, fruit juice TSS, vitamin C) and mechanical characteristics (weight loss percentage, sphericity coefficient, maximum shear force, maximum fracture force and maximum tensile strength of the fruit skin) were measured during storage.Results and Discussion The results of experiments showed that the trend of changes in vitamin C content decreased during storage. But this decrease was slower in the different percentages of chitosanclay, olive oil coating and carnoba wax than in the control samples.The results showed the significant differences at 1% and 5% levels between different coatings at maximum fracture force, percent weight loss and pH. In addition, the effect of storage times on TSS, pH and maximum fracture force was significant. The lowest and highest percentage of weight loss for uncoated samples and olive oil coating were 12.3% and 10.23%, respectively. Results showed that the coated fruits had the better performance in preserving the quality of properties than the uncoated samples and 5% chitosanclay nanocomposite coatings were higher performance than the other coatings.Conclusion In this study, the effect of chitosanclay nanocomposite, olive oil, Carnoba wax and uncoated samples during 12 days shelf life storage on Chemical characteristics (pH, citric acid, fruit juice TSS, vitamin C) and mechanical characteristics (weight loss percentage, sphericity coefficient, maximum shear force, maximum fracture force and maximum tensile strength of the fruit skin) were investigated. The results of this study showed that 5% chitosanclay nanocomposite coatings were higher performance than the other coatings.