The potential use of irradiation to extend the shelf‐life of clams (Ruditapes decussatus) during live storage: effect on bacterial and biochemical profiles

Abstract

SummaryChanges in microbiological and biochemical quality of clams (Ruditapes decussatus) subjected to low doses of gamma irradiation (0.5 and 1 kGy) were investigated during alive storage, at 5 °C. The mortality rate was significantly lower for irradiated clams compared with the control. In the same way, ammonia content was lower for irradiated clams (especially 1 kGy irradiated group). Considerable levels of total mesophiles, coliforms, staphylococcus, faecal streptococcus and Escherichia coli were detected in the control and irradiation had immediately reduced these charges; all bacteria studied experienced a 1‐ to 3‐log reduction following 1 kGy irradiation. At the last day of storage, irradiated groups showed a noticeable reduction in the bacterial counts, whereas the mesophiles, staphylococcus and coliform germs were abundant in the control group (6.3, 2 and 1.7 log CFU g−1, respectively). Irradiation doses up to 1 kGy had not an immediate effect on fatty acids composition (P > 0.05) and lipid profile was better in irradiated samples, where polyunsaturated fatty acid fraction was maintained throughout storage using irradiation. Also, sodium dodecyl sulphate‐polyacrylamide gel electrophoresis revealed minor changes in proteins bands between different samples. These results demonstrated that 1 kGy irradiation appeared to be the optimum dose for treating alive clams (R. decussatus), through improving the microbial quality and alleviating biochemical changes during refrigerated storage.