Effect of Gamma Irradiation on Microbial Control of Three Varieties of Apple

Three varieties of apple namely Red Delicious, Golden Delicious and Granny Smith were purchased from a garden located in Urmia city. Then, 100 aples of medium size (120-180 g) were randomly selected. The samples were put in sterile nylon bags and kept into refrigerator (4 °C) for one week. Afterwards, the samples were irradiated with doses of zero (control level), 250, 500, 750 and 1000 Gy by the use of gamma irradiation (Co60). Therefore, the samples were stored for 0, 60, 120 and 180 days under two conditions: storage condition (15±2 °C temperature and 80% relative humidity) and refrigerator condition (3±1 °C temperature and 90% relative humidity). Every two months, the samples were checked in terms of total microbes and fungi (yeasts and molds) and compared with control (unirradiated) samples. Results of the investigations indicated that the proper conditions in terms of microbial control in order to maintain the quality of apple varieties in 6 months of storage is the dose rate of 750 Gy at 4 °C temperature.