Abstract: To investigate the changes in the bacterial community and the dominant spoilage bacteria in chilled beef stored at 0 ℃, culture-dependent 16S rRNA gene sequencing and culture-independent high-throughput sequencing were carried out to detect the changes in bacterial diversity during the storage. The sensory score, protease activity, pH, and total volatile base nitrogen (TVB-N) in sterile beef extract inoculated with the isolates from spoiled beef were assessed for spoilage potential. The results showed that chilled beef maintained good sensory quality during the early period of storage, and it smelled unpleasant and rotten on the 15th and 18th day, respectively. Total viable count (TVC) rapidly increased during the first 15 days, reaching 8.73 (lg(CFU/g)), and then remained steady. The growth rates of Pseudomonas, Brochothrix thermosphacta, Enterobacter and lactic acid bacteria (LAB) exhibited similar trends to TVC, among which Pseudomonas grew fastest, while Enterobacter and LAB showed the slowest growth rate. The bacterial composition in chilled beef was complex and diverse, including B. thermosphacta, Acinetobacter spp., Aeromonas spp. and Pseudomonas spp., while it became simpler after spoilage. Pseudomonas especially P. fragi and B. thermosphacta were the dominant spoilage bacteria in spoiled beef stored at 0 ℃. Furthermore, these spoilage isolates, including 10 strains of Pseudomonas, 4 strains of B. thermosphacta and 1 strain of Hafnia alve, were separately inoculated to sterile beef juice. The samples inoculated with Pseudomonas and H. alvei exhibited higher sensory score, pH value and TVB-N content, revealing stronger spoilage potential, compared to B. thermosphacta. Moreover, Pseudomonas had stronger protease activity. Thus, the shelf-life of chilled beef was about 15 d based on sensory and microbial evaluation. During the storage, the microbial diversity decreased, and Pseudomonas and B. thermosphacta were the dominant spoilage bacteria in chilled beef. Pseudomonas presented stronger spoilage ability in vitro than B. thermosphacta.

Key words: beef, high-throughput sequencing, Pseudomonas, spoilage ability