Comparison of culture-dependent and independent techniques for characterisation of the microflora of peroxyacetic acid treated, vacuum-packaged beef.

The diversity of microflora associated with peroxyacetic acid (POAA) treated and untreated beef was investigated by 16S rDNA gene cloning, DGGE analysis and conventional bacterial cultivation. Following vacuum packaging, POAA treated and untreated meat samples were stored for up to 18 weeks at -1.5 degrees C. Each culture independent method showed Carnobacterium spp. to predominate on both POAA treated and untreated meat. However, 16S rDNA gene analysis also detected the presence of psychrotolerant Clostridium spp. in the POAA-treated beef. Culture-dependent analysis did not distinguish Carnobacterium spp. from Lactobacilli. Although culture-dependent analysis showed an increase in the ratio of Enterobacteriaceae to lactic acid bacteria from weeks 6-18 in the POAA treated compared with the untreated meat, the numbers of Enterobacteriaceae were significantly less on POAA treated than on untreated meat. The combination of data collected by culture-dependent and independent techniques provided the most robust approach for elucidating the efficacy of chemical sanitization of chilled vacuum-packaged beef. If conventional cultivation is used for monitoring bacterial spoilage of vacuum-packaged chilled meats it is recommended that culture methods specific for Carnobacterium and Clostridium spp. should be included in order to provide a more complete indication of microbial diversity.