Abstract: The purpose of this work was to investigate the characteristics and spoilage ability of dominant spoilage bacteria including Proteus vulgaris and Hafnia alvei isolated from lightly salted large yellow croaker stored at chilled temperature. The phenotypes, biochemical characteristics, carbon source utilization profiles and cell membrane phospholipid fatty acid (PLFA) compositions of the wo strains were observed. Further, sterile lightly salted fish pieces were inoculated separately with either of the strains and evaluated for changes in sensory, microbiological and chemical quality to explore their spoilage potential. The results showed that both strains grew at low NaCl concentration (≤ 4%) and pH 5–7. The overall carbon source utilization profile and dominant fatty acid components of Proteus vulgaris were similar to those of Hafnia alvei. At 5 ℃, the shelf lives of fish pieces inoculated with Proteus vulgaris and Hafnia alvei were 12 and 14 d, respectively. The total bacterial number at the end of spoilage (Nmax) were (8.90 ± 0.73) (lg(CFU/g)) and (8.70 ± 0.92) (lg(CFU/g)), and the yield factor (YTVB-N/CFU) values were 3.61 × 10-8 and 3.71 × 10-8 mg/CFU in the inoculated fish samples, respectively. Putrescine was less abundant than cadaverine in both samples, and alcohols and aldehydes were the main volatile components in them. In summary, there were some differences in physiological and biochemical characteristics between Proteus vulgaris and Hafnia alvei. Both strains had spoilage potential in lightly salted large yellow croaker and the spoilage potential of Proteus vulgaris was stronger than that of Hafnia alvei. This study provides a theoretical basis for processing optimization of lightly salted large yellow croaker and targeted inhibition of spoilage bacteria to prolong product shelf life.

Key words: lightly salted large yellow croaker, specific spoilage organisms, Proteus vulgaris, Hafnia alvei, spoilage potential, volatile compounds