اثر پرتودهي با نور فرابنفش C بر كاهش سرمازدگي ميوه خرمالو رقم كاشان طي انبارماني

Effect of UV-C radiation on alleviating chilling injuries of persimmon fruit cv. Kashan during cold storage

در اين مطالعه اثر پرتودهي نور فرابنفش C در شدت صفر (به‌عنوان شاهد)، 5 دقيقه پرتودهي از فاصله 15 و 30 سانتي‌متري به‌ترتيب با شدت 3/2 و 0/8 كيلوژول بر مترمربع و 10 دقيقه پرتودهي از فاصله 15 و 30 سانتي‌متري به‌ترتيب با شدت 16/4 و 4/1 كيلوژول بر مترمربع بر كاهش سرمازدگي و حفظ شاخص‌هاي كيفي خرمالو رقم كاشان در انبار طي سال‌هاي 1394 و 1395 و در دانشگاه بوعلي سينا مورد بررسي قرار گرفت. نتايج نشان داد كه پرتودهي روي كاهش وزن، شاخص سرمايي، نشت الكتروليت، پراكسيداسيون ليپيد و فعاليت پلي فنل اكسيداز در طول دوره انبارماني مؤثر بود. بيشترين درصد كاهش وزن (6/84) و شاخص سرمايي (40) در ميوه‌هاي پرتوتابي‌شده با 16/4 كيلوژول بر مترمربع مشاهده شد و سطح پايين پارامترهاي ذكر‌شده در تيمار 3/2 كيلوژول بر مترمربع ديده شد. سطح بالاي نشت الكتروليت (80/49) و پراكسيداسيون ليپيد (1/78 نانو مول بر گرم وزن ‌تر) در ميوه‌هاي تيمار‌شده با 4/1 و 16/4 كيلوژول بر مترمربع مشاهده شد و نيز سطح پايين پارامترهاي ذكر‌شده در ميوه‌هاي تيمار‌نشده و تيمار‌شده با 3/2 كيلوژول بر مترمربع به‌دست آمد. كاربرد پرتو فرابنفش C با دزهاي بالا فعاليت پلي فنل اكسيداز (9/7 واحد بر گرم وزن ‌تر) را در مقايسه با ديگر سطوح كاربردي پرتو فرابنفش C افزايش داد. با توجه به نتايج به دست آمده استفاده بعد از برداشت پرتو فرابنفش C در سطح پايين مي‌تواند عمر پس از برداشت خرمالوي كاشان را با كنترل علائم آسيب سرمايي و حفظ كيفيت ميوه افزايش دهد.

Background and objectives With increasing interest for developing the cultivation of persimmon, there is not suitable technology and enough information about postharvest behavior and storability of this fruit in many of countries such as Iran. Softening, chilling injury and the incidence of different diseases are limiting factors for postharvest life of persimmons fruits during cold storage. Ultraviolet-C (UV-C) light radiation has recently suggested to controlling decay and reducing chilling injury of some fruits. Therefore, this study was conducted to evaluate the effects of UV-C treatments with different doses on alleviating chilling injuries and maintaining qualitative attributes of persimmon fruits during storage. Materials and methods The persimmon fruits cv. `Kashan´ were harvested from a commercial orchard near Kashan city. UV-C treatments was carried out at 0 (as control), 5 minutes irradiation from 15 and 30 cm distance with 3.2 and 0.8 kJm-2, and 10 minute irradiation from 15 and 30 cm distance with 16.4 and 4.1 kJm-2. After 1, 2, 3 and 4 months, fruits were removed from storage and chilling injury indices, polyphenol oxidase (PPO) activity and some quality attributes were measured. Results The effect of UV-C treatments on weight loss, chilling index, electrolyte leakage, lipid peroxidation and PPO activity was effective during storage. High percent of weight loss (6.84) and chilling symptom (40) was observed in irradiated fruits with 16.43 kJm-2 and low level of mentioned parameters was seen in 3.2 kJm-2 treatment. High level of electrolyte leakage (80.49) and lipid peroxidation (1.78 nM g-1 FW) were detected in treated fruits with 4.1 and 16.43 kJm-2 and low level of above parameters were observed in non-treated and treated fruits with 3.2 kJm-2. Application of UV-C with high dose increased PPO activity (9.7 u gr-1 FW) in comparison to other treatments during storage. Discussion Our results suggest that application of UV-C irradiation in low level after harvest could increase postharvest life of `Kashan´ persimmon by controlling chilling injuries and preserving fruit quality. However, it is worth mentioning that chilling symptoms of persimmon was reduced by low doses of UV –C irradiation. In fact, UV-C treatment with high doses caused high percentage of injured fruits. In conclusion, the use of UV-C radiation in controlling chilling injuries and maintaining quality of persimmons fruits offers an interesting research area and considering the low risk of the treatments.