Preservation of Grass Prawns by Ionizing Radiation

The purpose of this study was to evaluate the feasibility of preserving grass prawns ( Penaeus monodon ) by ionizing radiation. Frozen prawns were irradiated with different doses at -10 ± 2°C. The threshold dose for detecting irradiation flavor was 4.5 kGy. The D₁₀ values for Vibrio cholera , Staphylococcus aureus , Escherichia coli , and Salmonella enteritidis were 0.11, 0.29, 0.39, and 0.48 kGy, respectively. Irradiation with doses of 2.5, 5.0, and 7.5 kGy reduced the total bacterial counts from 10⁵ CFU/g to 4.0 × 10³, 1.6 × 10³, and 3.2 × 10² CFU/g, respectively. The bacterial counts of the irradiated samples were below 10⁵ CFU/g throughout the storage periods studied. In contrast, the total bacterial counts of the unirradiated samples exceeded the marginal quality index (10⁶ CFU/g) after 48 d of storage at -10°C. The most significant changes in nutrients of irradiated frozen prawns were C_20:5, C_22:6, and thiamine, which decreased by 22, 25, and 32%, respectively. Other nutrients such as amino acids, saturated fatty acids, riboflavin, and niacin were relatively resistant to γ-irradiation within a dose range of 10 kGy. In summary, ionizing radiation can effectively reduce the number of microorganisms and preserve the quality of frozen grass prawns.