Abstract

In this study, chitosan coatings incorporated with propolis extract (PE) were utilized to extend the shelf-life of refrigerated Nemipterus japonicas fillets. Microbiological (total mesophilic bacteria (TMB) and psychrotrophic (PTC) count), physicochemical (pH, TVB-N, TBARS, FFA) and sensory (color, odor and preference) characteristics of coated fillets were evaluated during 12 days. The results showed that incorporating PE into chitosan could significantly (p<0.05) improve the quality of fish fillets. The results showed that the chitosan+PE samples reduced the extent of lipid oxidation, as judged by TBARS and FFA, suggesting that there is a synergistic effect between chitosan coating and propolis. Moreover, the application of chitosan coatings with PE improved the TVB-N and pH values of the Nemipterus japonicas samples significantly compared to untreated sample, thus extending the shelf life of Nemipterus japonicas fillet approximately >10 days. All wrapped fillets in treatment samples incorporated with PE had lower bacterial counts compared to control (p<0.05). However, the bacterial counts of chitosan coating combined with PE were lower than those treated by chitosan coating or PE alone during the storage. The fillets treated with chitosan and PE had the best sensory properties. The increase (>10 days) in the shelf-life was attributed to the antioxidant and antimicrobial characteristics of chitosan and PE. These results confirmed that chitosan coating enriched with PE can be an improving method to reducing deterioration of refrigerated Nemipterus japonicas fillets.

Keywords: Nemipterus japonicas, Chitosan, Propolis extract, Coating, Shelf life