تأثير محلول پاشي پس از برداشت اسانس آويشن بر عمر انبار ماني و كيفيت ميوه انار (رقم پوست قرمز طارم)

Effect of Postharvest Application of Thyme Essential oil on Quality and Shelf-life of Pomegranate (Punica granatum cv. Tarom red skin) Fruit

استفاده از اسانس های گیاهی به عنوان ایده ای جدید در كاهش ضایعات پس از برداشت و افزایش عمر انبارمانی محصولات باغبانی و كنترل آلودگی قارچی در كشاورزی توسعه یافته مطرح می باشد. در همین راستا، آزمایشی به منظور بررسی محلول پاشی اسانس آویشن بر عمر انبار مانی و كیفیت میوه انار رقم پوست قرمز طارم، به صورت فاكتوریل در قالب طرح كاملاً تصادفی با دو فاكتور، اسانس آویشن در چهار سطح (صفر، 500، 1000، 1500 میلی گرم در لیتر) و زمان در سه سطح (یك ماه، دو ماه و سه ماه انبارمانی) در دمای شش درجه سانتی گراد و رطوبت نسبی 85 درصد با چهار تكرار اجرا گردید. نتایج آزمایش انار های آلوده نشده با اسپور قارچ و انار های آلوده شده با اسپور قارچ نشان داد با افزایش مدت انبارمانی درصد كاهش وزن، درصد نشت یونی، درصد سرمازدگی و درصد پوسیدگی افزایش یافت. میوه های تیمار شده با اسانس آویشن آنتوسیانین بیشتری نسبت به شاهد داشت. اسانس آویشن از كاهش اسـید قابـل تیتراسیون و تجزیه آن به قندها جلوگیری كرد. اثر متقابل اسانس آویشن و زمان انبارمانی در انار های آلوده نشده با اسپور قارچ و انار های آلوده شده با اسپور قارچ نشان داد بیشترین كاهش وزن و نشت یونی در تیمار شاهد در ماه سوم انبارمانی بود. اثر متقابل اسانس آویشن و زمان انبارمانی در انار های آلوده نشده با اسپور قارچ نشان داد كمترین مواد جامد محلول در تیمار آویشن 500 میلی-گرم در لیتر در ماه دوم انبارمانی بود. اثر متقابل اسانس آویشن و زمان انبارمانی در انار های آلوده شده با اسپور قارچ نشان داد بیشترین اسیدتیه آب-میوه در تیمار شاهد در ماه سوم انبارمانی بود.

Introduction: Due to high quality, Iran pomegranate is quite competitive compared to other countries is unrivaled among agricultural products and has great economic importance. Using essential oil is a new idea to reduce postharvest losses and increase the horticultural crop storage life and control of fungal infection. In this context, a factorial experiment based on completely randomized design was conducted to study the postharvest spraying of thyme essential oil on storage life and qualitative characteristics of pomegranate fruit (cv. Tarom red skin) Materials and Methods: Pomegranate fruit (cv. Tarom red skin) was prepared and transferred to University of Zanjan, Horticulture postharvest physiology lab. Treatments were included essential oil of thyme at four levels (0, 500, 1000, 1500 mg/l) and the cold time storage (6 °C and 85% of relative humidity) at three levels (one, two and three months (by four replications. In the first experiment, 180 normal pomegranate fruits were treated with thyme essential oil. In the second experiment, fruits were infected with spores of the fungus Aspergillus niger and then treated with essential oil. During experiment, total soluble solids (TSS), titratable acidity (TA), TSS/TA ratio, pH, anthocyanin, electrolyte leakage, chilling injury, weight loss and fungal decay were evaluated. Fruit juice TSS was determined with a hand-refractometer at room temperature. TA was determined by titration an aliquot (20 mL) of the juice with 0.1 N NaOH and the results were expressed as a percentage of citric acid. The maturity index (TSS/TA ratio) was evaluated as the TSS/TA ratio. Fruit juice pH was measured using a pH meter. Anthocyanin was performed to method Fuleki & Francis. Electrolyte leakage was measured according to McCollum & McDonald method. Weight loss was measured according to Ershadi method. Chilling injury was measured by Wang method. Decay was visually evaluated and expressed as percentage. An analysis of variance was used to analyze difference between treatments and the Duncan test was applied for mean separation at p <0.05. All analyses were done with SAS statistical software. Results and Discussion: Results showed that chilling injury and fungal decay increased by storage time in both infected and no infected fruits, while this trend was slower in non-infected ones. Treated fruits by essential oil of thyme had more anthocyanin in comparison to control fruits. Essential oil of thyme prevents the reduction of titratable acid and catalysis of sugars. An interactive effect of treatments showed that weight loss and electrolyte leakage was the highest in control at the third month of storage. Interaction between essential oil of Thyme and storage time in pomegranates not infected with fungus spore showed the lowest TSS in essential oil of thyme (500 mg/l) in second month of storage. Essential oil of thyme reduces decay and increases the storage life of the fruits. It seems that the phenolic compounds of thyme essential oil form molecular hydrogen bound with the cytoplasmic membrane proteins of fungus and make them inactive. Essential oil of thyme has a positive effect in controlling weight loss during storage of pomegranates. Essential oil forms a thin layer of the skin that covers fruit and prevents water evaporation from the skin and keeps skin moisture. It also, maintains fluidity of the plasma membrane and prevents disintegration. So electrolyte and substances leakage of vacuole into the cytosol and the cytoplasmic space is controlled. One of the constituents of essential oil of thyme is phenolic compounds that are rich in carbonyl group. Carbonyl group has ability to disintegrate the free radicals formed by cold stress resulted in reduction of chilling injury in the fruit tissue. Essential oil has antioxidant that prevents anthocyanin oxidation during storage time. Meanwhile, the probably conversion of other competent compounds to anthocyanin caused an increasing of total water-soluble anthocyanin during storage time. Conclusion: Results showed that Thyme essential oil has positive impact on reducing chilling injury and electrolyte leakage also, controlling weight loss and fungal decay of pomegranate fruit. Nowadays, production of organic fruit are increasing because of their role in human health, hence by maintaining the fruit quality during storage time it can be used as a substitute for chemical compounds and fungicides.