Activities of strains of Brochothrix thermosphacta in vitro and in meat

Ninety three isolates of Brochothrix spp. from raw meat were analysed by PCR-based molecular fingerprinting and identified by species-specific Real-Time (RTi)-PCR and 16S rRNA gene sequencing. Thirty three strains were characterized for their growth capability in sarcoplasmic extract with and without glucose, for in vitro lipolytic activity, in vitro and in situ (in beef) proteolytic activity and for amino-decarboxylase activity. Moreover, spoilage potential of seven selected strains in sterile and non-sterile meat was investigated by analyzing the release of volatile organic compounds (VOCs) during storage in air. All the strains analysed were unable to hydrolyze sarcoplasmic proteins in vitro and in situ and they did not show lipolytic activity at 4. °C or 20. °C. Almost all were able to grow in the presence of sarcoplasmic extract with glucose and produced histamine. The release of VOCs by each strain in sterile and non sterile beef stored at 4. °C in air was evaluated by HS-SPME-GC/MS analysis. Acetoin and 1-octen-3-ol and 3-methyl-1-butanol were the major compounds isolated from sterile and non-sterile meat samples inoculated with single strains of Brochothrix (B.) thermosphacta and high concentration of acetoin was found in all inoculated meat samples. The role of B. thermosphacta as meat spoiler does not seem to be influenced by indigenous microbiota of meat while its development in meat is associated to a significant increase (P. <. 0.05) of acetoin and other compounds recognized as important contributors to the spoilage of meat and meat products.