Changes in the physicochemical properties of grouper (Epinephelus coioides) fillets stored under vacuum packaging at chilly temperature contributing with the spoilage bacteria

Abstract

Microbial activity is the primary and inevitable factor contributing to seafood spoilage. To assess the spoilage potential of dominant bacteria (Hafnia paralvei and Aeromonas allosaccharophila) isolated from spoiled vacuum-packed grouper fillets under cold storage. In this study, the total viable count (TVC), total volatile basic nitrogen (TVB-N), pH, trichloroacetic acid (TCA)-soluble peptides, water-holding capacity (WHC), nucleotide catabolism, free amino acids (FAAs), and volatile compounds (VOCs) of grouper fillets in vacuum packaging under cold storage with different bacteria inoculated (H. paralvei inoculated, A. allosaccharophila inoculated, and H. paralvei &A. allosaccharophila inoculated) were characterized. The results revealed that H. paralvei exhibited stronger degradation activity, leading to decreased water-holding capacity and increased levels of TVB-N and TCA-soluble peptides. Amino acid analysis showed distinct metabolic patterns for H. paralvei and A. allosaccharophila, with H. paralvei showing a high potential for utilizing FAAs. Both H. paralvei and A. allosaccharophila caused nucleotide catabolism, but A. allosaccharophila produced more hypoxanthine riboside and hypoxanthine. In addition, the analysis of VOCs indicated that H. paralvei produces large content of aldehydes in the middle of storage, particularly benzaldehyde. In addition, the grouper fillets inoculated with H. paralvei &A. allosaccharophila showed similar physicochemical changes to that inoculated with H. paralvei. In conclusion, H. paralvei emerged as the key bacteria responsible for spoilage in vacuum-packed grouper. This study is helpful in further understanding the relationship between spoilage microorganisms and the quality of grouper fillets, thereby providing valuable information for their preservation.