Enumeration of Meatborne Spoilage Bacteria with Hydrophobic Grid Membrane Filtration ^†

Hydrophobic grid membrane filtration (HGMF) was investigated as an alternative to conventional plate counts for enumerating spoilage bacteria recovered from raw beef. The HGMF method was compared to conventional procedures for the selective enumeration of total psychrotrophic bacteria, pseudomonads, total Enterobacteriaceae . Brochothrix thermosphacta , and lactic acid bacteria. Bacteria were recovered both from beef which had been artificially inoculated with identified strains and from naturally contaminated beef from a commercial abattoir. There were no significant differences (P > 0.05) in numbers of any bacterial group recovered from naturally contaminated beef using HGMF procedures when compared to conventional plating on selective media. The recoveries of the total psychrotrophic population, Escherichia coli . B. thermosphacta , and Lactobacillus sake inoculated onto meat were unaffected by the enumeration procedure (P > 0.05). However, the populations of Pseudomonas sp. recovered from inoculated beef by a HGMF procedure were 0.8 log cycles lower (P < 0.05) when compared to the conventional spread plate procedure.