Efficacy of lyophilized cell-free supernatant of Lactobacillus salivarius (Ls-BU2) on Escherichia coli and shelf life of ground beef

In the present study, the effect of different concentrations of cell-free supernatant (CFS; 10.00 and 35.00 mg g^-1) of Lactobacillus salivarius (Ls-BU2) on chemical, microbial and sensorial specifications of ground beef stored under the refrigerated condition was investigated. The antibacterial activity of CFS on Escherichia coli was also assessed. According to agar-disk diffusion method, CFS of Ls-BU2 revealed a promising antibacterial activity against E. coli in culture media compared to CFS of a well-known probiotic (L. acidophilus LA-5). In meat, CFS of Ls-BU2 showed a minimal effective concentration (MEC) of 35.00 mg g^-1 on E. coli, while CFS of L. acidophilus represented a MEC of 45.00 mg g^-1. The CFS of Ls-BU2 at 35.00 mg g^-1 concentration retained psychrophilic counts of meat at a lower value than maximum accepted level (7 log10 CFU g^-1). In a similar trend, CFS of Ls-BU2 at 35.00 mg g^-1 concentration was also displayed high sensorial scores compared to other CFS-treated samples. In conclusion, we demonstrated that CFS of Ls-BU2 and to some extent CFS of L. acidophilus could act as a safe food additive for the control of bacterial pathogens and to extend the shelf life of ground beef.