Effects of gamma radiation on the postharvest properties of oyster mushroom (Pleurotus sajor-caju (Fr.) Singer)

This thesis studies the possibility of using gamma irradiation in preserving oyster mushrooms (Pleurotus sajor caju (Fr.) Singer).Fresh mushrooms were collected and irradiated at 25, 50, 75 and 100 krad. Samples were kept at two storage temperatures - ambient room temperature (27-33 degrees Centigrade) and refrigeration (8-10 degrees Centigrade). Weight loss, percent crude protein, percent reducing sugar and microbial load were analyzed at different times of post harvest storage, and compared with a control. The organoleptic qualities like color, aroma, texture, flavor as well as general acceptability were evaluated by a sensory panel. Results showed that gamma irradiation did not affect the crude protein content of the oyster mushrooms. However, the reducing sugar content of the mushrooms was affected by irradiation on the first day of storage but not on the third day. The microbial load and weight loss were also found to be significantly reduced by irradiation if kept at temperature of 8-10 degrees Centigrade. Although the organoleptic properties such as color, aroma and texture were affected by irradiation, the irradiated mushrooms were as acceptable as the unirradiated ones. The shelf life of irradiated mushrooms kept at low temperature was extended up to 20 days while those kept at room temperature were decayed and rotten on the third day. At 25 krad, the microbial load and shelf-life extension of oyster mushroom gave the same results as compared to those exposed to higher doses of 50, 75 and 100 krads