Comparison of membrane filtration rates and hydrophobic grid membrane filter coliform and Escherichia coli counts in food suspensions using paddle-type and pulsifier sample preparation procedures.

Food suspensions prepared by Pulsifier contained less debris and filtered 1.3x to 12x faster through hydrophobic grid membrane filters (HGMFs) than those prepared by Stomacher 400. Coliform and Escherichia coli counts made by an HGMF method yielded 84 and 36 paired samples, respectively, positive by both suspending methods. Overall counts of pulsificates and stomachates did not differ significantly for either analysis, though coliform counts by Pulsifier were significantly higher in mushrooms and significantly lower in ground pork (P = 0.05). Regression equations for log10 counts of coliform and E. coli by Pulsifier and Stomacher were: Pulsifier = 0.12 + 0.97 x Stomacher, and Pulsifier = 0.01 + 1.01 x Stomacher, respectively.