Abstract: Traditional microbial counting methods, high-throughput sequencing, the Kjeldahl method and high performance liquid chromatography (HPLC) were applied to explore the effects of different postmortem storage times of beef (0, 12, 24 and 36 h at 0–4 ℃) on microflora changes and proteolysis during the processing of fermented beef sausages as well as on the correlation between them. The results showed that the total number of bacterial colonies, coliform count, the diversity and richness of bacterial communities and proteolysis indexes increased, while the content of total free amino acids in fermented beef sausages decreased as the storage time of raw beef increased. A significant positive correlation appeared between total volatile basic nitrogen (TVB-N) and total biogenic amine contents during the ripening process (P < 0.01). The average values of total number of bacterial colonies and Shannon?diversity index of fermented sausage prepared from 36 h-chilled beef were 4.03 × 107 CFU/g and 2.89, respectively, which were both higher than those (2.40 × 107 CFU/g and 1.39) of fermented sausage prepared from unchilled fresh beef (P < 0.05 for total number of bacterial colonies). The dominant bacteria in the former were Staphylococcus over the whole processing period, while the dominant bacteria in the latter were Weissella spp. at the early stage and Staphylococcus at the late stage. The average total free amino acid content decreased from 7.09 to 6.44 mg/g, whereas the average total biogenic amine content increased from 92.14 to 117.42 mg/kg (P < 0.05). These results indicated that controlling the storage time of raw beef could effectively reduce the total microbial load and the microbial diversity of fermented sausages, retard the accumulation of biogenic amines and inhibit proteolysis, thereby ensuring the safety of fermented sausages.

Key words: fermented beef sausage; microorganism; nitrogen-containing compound; biogenic amine