Carnobacterium maltaromaticum isolated from vacuum-packed beef with long shelf life: morphological and functional characterization

This study was conducted as part of a research project on meat conservability, in particular vacuum packaged beef displaying very long shelf lives at a temperature close to the freezing point, and its objective was to perform a morphological and functional characterization of C. maltaromaticum with potential bioprotective effect isolated from vacuum packaged long shelf life beef. The isolated C. maltaromaticum strain presented similar morphological, biochemical and enzymatic profiles as those of two reference strains (LMG 11393 and LMG 22902). Among the studied conditions, a temperature of +12 °C and an atmosphere poor in oxygen (100 % N2) were the optimal conditions for the growth of C. maltaromaticum. Nevertheless, growth on lower temperatures is also possible. After inoculation of beef samples with C. maltaromaticum and 7 days of storage under vacuum at −1 °C, no effect was observed on the total viable count and on the count of lactic acid bacteria. A reduction of Pseudomonas sp. and Brochothrix thermosphacta was observed during the first week of storage under vacuum conditions. After 7 days of subsequent storage of the same samples under modified atmosphere at +4 °C, the inoculant favored the growth of B. thermosphacta and inhibited the growth of Enterobacteriaceae under 100 % N2. No effect of the inoculant was observed when an atmosphere rich in oxygen was applied. The evaluation of the influence of different atmospheres showed that the growth of C. maltaromaticum was slower in an atmosphere containing O2 and CO2. Long-term storage under vacuum at low temperatures are therefore suitable for the growth of this bacterium. An antimicrobial effect against Enterobacteriaceae was highlighted on inoculated fresh meat stored under N2. The functional characterization of this strain will be further pursued by genotypic characterization. Special attention will be taken to study its bioprotective properties.