Membrane filtration method for enumeration and isolation of Alicyclobacillus spp. from apple juice

Aim: To evaluate the applicability of filtration membranes for detecting Alicyclobacillus spp. spores in apple juice. Methods and Results: Ten types of nitrocellulose membrane filters from five manufacturers were used to collect and enumerate five Alicyclobacillus spore isolates and results were compared to conventional K agar plating. Spore recovery differed among filters with an average recovery rate of 126 center dot 2%. Recovery levels also differed among spore isolates. Although significant difference (P < 0 center dot 05) in spore sizes existed, no correlation could be determined between spore size and membrane filter recovery rate. Conclusions: Recovery of spores using membrane filtration is dependent on the manufacturer and filter pore size. Correlations between spore recovery rate and spore size could not be determined. Significance and Impact of the Study: Low numbers of Alicyclobacillus spores in juice can be effectively detected using membrane filtration although recovery rate differences exist among different manufacturers. Use of membrane filtration is a simple, fast alternative to the week-long enrichment procedures currently employed in most quality assurance tests.