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 th ose 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 di d not differ signiticantly for either analysis, though coliform counts by P ulsifier were significantly higher in mushrooms and significantly lower in ground pork (P = 0.05). Regression equations for log(10) counts of coliform and E. coli by Pulsifier and Stomacher were: Pulsifier = 0.12 + 0.97 x Sto macher, and Pulsifier = 0.01 + 1.01 x Stomacher, respectively.