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

Abstract

In the present study, the effect of different concentrations of cell-free supernatant (CFS; 10.00 and 35.00 mg g^-1) of <em>Lactobacillus salivarius</em> (Ls-BU2) on chemical, microbial and sensorial specifications of ground beef stored under the refrigerated condition was investigated. The antibacterial activity of CFS on <em>Escherichia coli</em> was also assessed. According to agar-disk diffusion method, CFS of Ls-BU2 revealed a promising antibacterial activity against <em>E. coli</em> in culture media compared to CFS of a well-known probiotic (<em>L. acidophilus</em> LA-5). In meat, CFS of Ls-BU2 showed a minimal effective concentration (MEC) of 35.00 mg g^-1on <em>E. coli</em>, while CFS of <em>L. acidophilus</em> represented a MEC of > 45.00 mg g^-1. The CFS of Ls-BU2 at 35.00 mg g^-1concentration 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^-1concentration 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 <em>L. acidophilus</em> could act as a safe food additive for the control of bacterial pathogens and to extend the shelf life of ground beef.