Combined Effect of Gamma Irradiation and Low Temperature Storage on the Microbial and Bio-chemical Quality of Sutchi Cat Fish (Pangasius hypophthalmus)

Gamma irradiation is known as an effective method to reduce microbial contamination in food products. Its application in seafood food not only enhances safety and quality but also extends shelf life, thereby minimizing post-harvest losses. This study focuses on evaluating the combined effect of low dose gamma irradiation and low-temperature storage on the quality and shelf life of fresh Sutchi Catfish (Pangasius hypophthalmus). The fish samples were subjected to different gamma irradiation doses (0.0 kGy, 1.0 kGy, 3.0 kGy, and 5.0 kGy) and then stored under refrigerated conditions (4°C) and frozen conditions (-18°C). Both non-irradiated and irradiated samples were periodically analyzed for microbial counts, including coliforms (total and fecal), total mesophilic bacteria, Salmonella, E. coli, and Staphylococcus aureus. The biochemical quality indices such as total volatile base nitrogen (TVB-N), pH, peroxide value (PV), and thiobarbituric acid reactive substances (TBARS) were also assessed at regular intervals. The findings revealed that the gamma irradiation and storage at low temperatures significantly (p < 0.05) reduced microbial populations, with higher irradiation doses resulting in greater reductions. Chemical quality indicators in irradiated samples were notably better maintained compared to the control samples under both storage conditions. The study concluded that combining gamma irradiation with refrigeration or freezing effectively minimized microbial loads and preserved biochemical quality. This approach extended the shelf life of the fish up to 21 days in refrigeration and 90 days under frozen storage conditions.