بررسي امكان حفظ كيفيت ميوه پرتقال تامسون‌ناول (Citrus sinensis cv. Thomson Navel) با استفاده از تيمارهاي پوششي در انبار معمولي

Investigation of quality preservation of Thomson navel orange (Citrus sinensis cv. Thomson Navel) using of coating treatments in common storage

نقش انبار و پوشش ميوه‌ها در حفظ ارزش غذايي و افزايش عمر انباري ميوه پرتقال تامسون اهميت دارد. در اين پژوهش ميوه پرتقال تامسون بعد از پوشش‌دهي (واكس پلي اتيلن، واكس براق كننده، واكس انباري، واكس Britex Ti، پاكت فريزر، قارچ‌كش تكتو 60 و بدون پوشش) به مدت سه ماه در انبار معمولي (دماي 12-5 سانتي‌گراد و رطوبت نسبي 75-85 درصد) نگهداري شد. به فاصله هر 30 روز با نمونه‌برداري از انبار خصوصيات فيزيكوشيميايي و حسي ميوه ارزيابي شد. نتايج نشان داد كه در كليه‌ي تيمارها با كاهش وزن، درصد آبميوه نيز كاهش يافت ولي ميوه‌هاي پوشش داده شده با پاكت فريزر بيشترين درصد آبميوه (4/38 درصد) و كمترين كاهش وزن (04/1 گرم) را داشتند. ميزان ضايعات در 30 روز اول انبارداري و در تيمار با پاكت فريزر افزايش يافت. شاخص‌هاي رنگ (L*, c, h) طي نگهداري در كليه تيمارها در حد استاندارد بود. بطوركلي نسبت TSS/TA طي نگهداري افزايش معني‌داري داشت ولي در تيمار شاهد با ميانگين 14/16 در بالاترين سطح بود. بيشترين مقدار فنل‌كل مربوط به تيمار پاكت فريزر با مقدار 71/0 ميلي‌گرم در گرم بود. مقدار آسكوربيك‌اسيد تا انتهاي دوره انبارداري در ميوه‌هاي تيمار شده با Britex Ti با مقدار 33/42 ميلي‌گرم بر 100 گرم نسبت به شاهد افزايش يافت. ظرفيت آنتي‌اكسيداني در پوست و گوشت بجز تيمارهاي شاهد و پاكت فريزر افزايش يافت. تيمارهاي واكس انباري و بريتكس نقش موثري در حفظ خصوصيات كيفي ميوه داشتند ولي بر اساس ارزيابي حسي، پوشش پاكت فريزر جداي از ميزان ضايعات بالا اثر مطلوب بيشتري روي كيفيت ميوه داشت.

Introduction: Thomson orange is an important citrus verity which cultivated and produced widely in the north and south of Iran. The extra part of this production is stored in the common storage for several monthsespecially in the north area. The role of storage and fruit coating are important due to maintain the nutritional value and enhancing the ‘Thomson’ orange storage life. The aim of this study was to investigate the possibility of maintainingthe fruit quality using coatingtreatmentsin common storage. Materials and methods: In this experiment the harvested fruits were divided in to seven groups randomly, then thefruits of each group were treated using different coating (Polyethylene wax, Shine wax, Storage-wax, Britex Ti wax, Freezer bag, Fungicide ‘Tecto 60’) and Control group without any coating. All the groups were stored in the common storage (5-12 oC and 75-85% RH) for tree month. Some physicochemical and sensory characteristics were investigated including percentage of juice, weightless, losses rate, total soluble solid (TSS), titratable acidity (TA), TSS/TA, peel and pulp total phenolics, ascorbic acid, antioxidant activity in peel and pulp, color indices (L*, chroma and hue angle), peel and pulpAppearance, aroma, flavor, sweetness, sourness, off-flavor, bitterness, acceptance of the fruit each 30 days intervals during storage Results and discussion: Results showed that, the juice percentage declined with decreasing of weight loss in all treatments, but the fruits which treated by freezer bag had the highest juice percentage (38.4%) and the lowest weight loss (1.04 g). Weight loss in Citrus fruit depended on the length and storagetemperature during storage and usually increased on low moisture conditions.Therefore, fruits which packed by polyethylene bags were resistance to water loss through surface peel as well as during storage. The losses increased during the early month of storage especially in freezer bags and shine wax treatments by 4.67 and 3.33% respectively. It seems that bags inner spaceis suitableatmosphere for growing of peniciilium fungi. Color indices (L*, c, h) were in optimum range in all treatments during storage. The length of storage had no significant effect on total soluble solid but affected significantly using coating treatments than control. Moreover, the titratable acidity gradually declined during storage but wax coating maintained TA value higher than other treatments significantly. Overall, the TSS/TA level was increased during storage and the highest ratio (16.14) was observed in control. The increase in TSS/TA was due todecreasing of acidityandincreasing of polysaccharidesduring storage. The total phenolics content decreased in all treatment in peel and pulp as the highest phenolics content with 0.71 mg.g-1 occurred in freezer bag treatment. The amount of ascorbic acid were increased with 42.33 mg.100gr-1 in fruits which treated by Britex Ti wax than control at the end of storage. It seems that lower observation ofascorbic acid in coating treatment due to reduction of the oxygen molecules in fruit tissue by coating. Antioxidant capacity was increased in both peel and pulp of fruits, except in the freezer bag and control treatments. The freezer bag treatment had highest sweetness 7.22 and lowest sourness 1.79 compared to the other treatments and the control. The Britex Ti treatment had the highest level of off-flavor (2.15) and bitterness (1.56) compared to the other treatments and the control. The freezer bag treatment had the highest score (8.09) in the acceptance of the fruit, compared to the other treatments. Conclusion: According to physiochemical and sensory evaluation, Britex Ti, storage-waxes and freezer bag treatments had positive influences on fruit quality in common storage.Thereforethe Storage-wax which produced by the internal companies,it is preferable to be use by citrus growers to maintaining the fruits quality in the common storage.