author(s)
Bipul Kumar Kakati, Inam Akhtar Hussain and Umesh Ch. Goswami

abstract
The effect of gamma (cobalt-60) irradiation (3 and 5 kGy) on the microbial safety and biochemical quality of fermented Phassya Shidal, which was vacuum-packed in polyethylene bags and stored under ambient temperature was studied by measuring microbiological and biochemical changes in six months of storage. Gamma irradiation had significant effects (P<0.05) on the reduction of microbial populations making the product safe and free from the possibilities of food poisoning. Coliform count was detected in the case of irradiated samples, only after the fourth month of storage. No yeasts and moulds were detected in irradiated samples at 3 kGy until the end of 5th month and at 5 kGy at the end of the 3rd month of storage. Salmonella spp. were not detected in all irradiated and control samples throughout the storage period. The moisture content of control and irradiated Shidal samples (3 kGy & 5 kGy) was recorded as 38.80%, 35.86% and 34.46%, respectively and showed significant decrease (P<0.05) after irradiation. There is increase of protein, fat and ash content after treatment. Though the biochemical analysis showed little loss in the nutritional quality of Shidal after treatment and the subsequent storage period, yet the products remained in an acceptable condition. As the higher doses of gamma irradiation effect the changes of nutritional quality more, therefore, low dose irradiation i.e. 3 kGy may be recommended as a safe preservation method for the fermented fish product Shidal.