Improving the Quality of Silver Carp Fish Fillets by Gamma Irradiation and Coatings Containing Rosemary Oil

The objective of this work was to study the combined effect of gamma irradiation and coatings containing 0.5% rosemary (Rosmarinus officinalis) essential oil (RO) on the chemical, microbiological, and sensorial qualities of silver carp (Hypophthalmichthys molitrix) fish fillets (SFF) during cold storage (4 degrees C). SFF were divided into three groups: uncoated (control), coated with edible coating (without additives), and -irradiated (0, 1, 3, and 5kGy) coated with coating containing 0.5% rosemary. Gamma irradiation at 1, 3, and 5kGy with coating reduced the initial total bacterial count, psychrophilic bacteria, and lactic acid bacteria and prolonged shelf life of the samples. Coated samples irradiated at 1kGy reduced the counts of Enterobacteriaceae, Staphylococcus aureus, and Bacillus cereus, as well as eliminating Vibrio spp. and Salmonella spp., while coated samples irradiated at 3 and 5kGy completely eliminated these bacteria. Combined treatment showed a slight increase in thiobarbituric acid-reactive substances postirradiation during cold storage but had no effect on the total volatile basic nitrogen and trimethylamine contents, while a gradual increase in these chemical quality indices was observed during cold storage. Combined treatment had no adverse effects on the sensory properties of SFF. The increase in the bacterial inhibitory effect is caused by both rosemary oil and irradiation.