اثر پوشش کیتوزان و نانوفیبر ‌کیتوزان بر کیفیت و انبارمانی میوه‌ی ‌‌توت‌فرنگی رقم پاروس

توت‌فرنگی به‌دلیل داشتن بافت نرم و حساسیت فراوان به پاتوژن‌ها عمر انباری کوتاهی دارد. ازجمله راه‌های نامناسب برای افزایش ماندگاری آن استفاده از ‌‌ترکیبات شیمیایی مصنوعی و ضدقارچی می‌باشد که اثر سوء بر سلامت مصرف‌کننده و محیط‌زیست بر جا می‌گذارند‌. این پژوهش جهت بررسی اثر پوشش‌دهی با کیتوزان و نانوفیبر کیتوزان ‌بر عمر انباری و برخی ویژگی‌های کمی و کیفی میوه‌ی توت‌فرنگی رقم پاروس طی نگهداری در انبار سرد، در قالب یک آزمایش فاکتوریل بر پایه طرح کاملاً تصادفی با دو فاکتور و سه تکرار انجام گرفت‌. فاکتور اول تیمار‌ها (به‌صورت 2 دقیقه غوطه‌وری) در 5 سطح شامل شاهد خشک، آب مقطر، کیتوزان 0.5 درصد، نانوفیبر کیتوزان 0.2 درصد و نانوفیبر کیتوزان 0.5 درصد و فاکتور دوم زمان انبارداری در 5 سطح شامل: صفر، 5، 10، 15 و 20 روز بود‌. نمونه‎‌ها پس از خشک شدن، در ظروف ‌یک‌بار مصرف پلاستیکی بسته‌بندی و در دمای 4 درجه سلسیوس و رطوبت نسبی 85 تا 90 درصد نگهداری شدند‌. نتایج نشان داد میوه‌های تیمار شده با 0.5 درصد نانوفیبر کیتوزان، سفتی بافت، tss، ویتامین ث، آنتوسیانین و فنل کل و فعالیت آنتی‌اکسیدانی بالاتری نسبت به میوه‌های شاهد طی دوره انبار داشتند. هم‌چنین درصد پوسیدگی در میوه‌های تیمار شده با 0.5 و 0.2 درصد نانوفیبر کیتوزان به‌ترتیب 61 درصد و 55 درصد کمتر از میوه‌های شاهد بود. براساس نتایج این مطالعه، پوشش نانوفیبر کیتوزان می‌تواند به‌عنوان یک پوشش دوست‌دار محیط زیست در کنترل پوسیدگی توت‌فرنگی و حفظ کیفیت آن در انبار مورد‌استفاده قرار بگیرد.

effect of chitosan and chitosan nanofiber coating on quality and storability of strawberry fruit cv. paros

introduction:postharvest fungal diseases can limit the storage period and shelf life, and thus market life of fruit and vegetables, which results in serious economic losses worldwide. despite the efficacy of synthetic fungicides in the control of postharvest decay, public concerns about chemical and toxic residues in food and the increase in drug-resistant strains of many pathogens indicate the need for development of new strategies. coatings and packaging materials have been considered as another method for increasing the postharvest storage time of fruits and vegetables. chitosan-based nano composites are proper alternatives to mitigate the negative impacts of conventional coatings and films on human and environmental health. additionally, natural chitosan coatings and packaging incorporated with functional compounds decrease the postharvest losses of fruits and vegetables without changing their nutritive and sensorial properties. therefore, the current research work was performed to investigate the effectiveness of chitosan and chitosan nanofiber on the quality and storability of strawberry fruit cv. paros. material and methods:this study was conducted in the form of a factorial experiment based on a completely randomized design with two factors and three replications. the first factor was treatments in 5 levels including dry control, distilled water, chitosan 0.5%, chitosan nanofibers 0.2% and chitosan nanofibers 0.5% and the second factor was storage time in 5 levels including: zero, 5, 10, 15 and 20 days. the treatments were applied as a 2-minute immersion of the fruits in the prepared solution at ambient temperature (25 ° c), and the samples were stored after drying in plastic disposable containers at 4°c and relative humidity of 85 to 90%. at the end of the storage periods, the values of weight loss, ph of fruit juice, total soluble solids, titratable acidity, and firmness of fruit tissue, color indexes, total anthocyanin, total phenol content, vitamin c content, antioxidant activity and percentage of decay of the aforementioned treatments were evaluated. results and discussion:the results showed that at the end of the storage period, the 0.5% chitosan nanofiber treatment was able to maintain the ta value 77% higher than the control at same-day. also, the tss of 0.5% and 0.2% chitosan nanofiber treatments was lower than the control, which indicates a delay in the tissue softening of coated fruits due to a lower breakdown of sugars. on the 20th day of storage, the ph, tss/ta, and the percentage of weight loss in the treatment of 0.5% chitosan nanofiber were lower than the control; the explanation for the rise in ph of control fruits is due to the decrease in organic acids and potential sugar conversion. the highest value of firmness between treatments was found in the 0.5% chitosan nanofiber treatment (3.11 newton) after 20 days of storage. the semi-permeable surface of coated fruits may have contributed to fruit firmness persistence by limiting metabolic gaseous exchange (oxygen and carbon dioxide) across the coating barrier, followed by a decrease in metabolic activity and oxidizing enzyme effectiveness. the highest content of vitamin c, total phenol, and total anthocyanin were in the 0.5% chitosan nanofiber treatment, which showed a significant difference from other treatments. at the end of storage, the percentage of antioxidant activity of fruits in coating treatments including 0.5% chitosan nanofiber, 0.2% chitosan nanofiber, and 0.5% chitosan, 25%, 14%, and 5%, respectively, was higher than the dry control. higher contents of color indexes including lightness (l*), redness (a*), yellowness (b*) and chroma, and lower values of hugh angle were observed in fruit coated with chitosan nanofiber. the percentage of decay in chitosan nanofiber-treated fruits (0.5% and 0.2%) and chitosan (0.5%) decreased by 61%, 55%, and 43% more than the control, respectively.conclusions:the present study found that using a 0.5% chitosan nanofiber coating was the most effective way to maintain the quality of strawberries during storage for up to 20 days. it allowed good preservation quality such as weight loss, decay, antioxidant activity, firmness, color, vitamin c, anthocyanin content, and total phenolic compounds. however, 20 days is a sensitive period for the commercialization of strawberries, considering the normal time of 7–14 days is generally accepted. consequently, various storage strategies can be applied to suit the market needs.