Isolation of Alicyclobacillus acidoterrestris from fruit juices.

K agar, a novel isolation medium developed for the food industry, was compared with other acidified media for isolation of Alicyclobacillus acidoterrestris spores. Spores were inoculated into apple juice, orange juice, and a fruit juice blend and then isolated on the following media: K agar, pH 3.7; semi-synthetic medium, pH 4.0; orange serum agar, pH 3.5; and minimal salts medium, pH 4.0. Media were incubated at 24, 35, 43, and 55 degrees C. Highest recovery of spores was obtained with either K agar or semi-synthetic medium, incubated at 43 degrees C. The effect of heat shocking spores at different times was also determined; heat shocking at 80 degrees C for 10 min was considered appropriate. Peptone, previously shown to inhibit A. acidoterrestris, was not inhibitory when present in K agar. A collaborative trial with 9 laboratories was undertaken to determine the repeatability and reproducibility of counts on K agar. K agar prepared from individual components was compared with dehydrated K agar prepared by International BioProducts (Redmond, WA). There were no significant differences between log mean counts for the 2 media for each of the juices analyzed at both the high and the low inoculum levels. Repeatability and reproducibility values were not significantly different either within juices, within trials, or across all samples tested in both trials. K agar is suitable for isolation of A. acidoterrestris spores from fruit juices.

Efficacy of oxonia active against selected spore formers.

Alternatives to hydrogen peroxide are being sought for use in aseptic packaging systems because this sterilant is efficacious at temperatures higher than some of the newer packaging materials can tolerate. Earlier in this century, peracetic acid was known to be bactericidal, sporicidal, and virucidal but was not widely used because of handling, toxicity, and stability problems. Sanitizer suppliers have capitalized on the efficacy of hydrogen peroxide, acetic acid, and peracetic acid stabilized with a sequestering agent. Formulations have been improved and marketed as Oxonia Active, and its use as an alternative sterilant to hydrogen peroxide merits evaluation. Oxonia was assessed at a concentration of 2% and a temperature of 40 degrees C against a number of spore-forming organisms, including foodborne pathogens. Spores tested in aqueous suspension showed an order of sensitivity (least to greatest) to Oxonia as follows: Bacillus cereus > B. subtilis A > B. stearothermophilus > B. subtilis var. globigii > B. coagulans > Clostridium sporogenes (PA3679) > C. butyricum > C. botulinum type B (nonproteolytic) > C. botulinum type B (proteolytic) = C. botulinum type A = C. botulinum type E. B. subtilis A and B. stearothermophilus spores tested in the dry state were less sensitive to Oxonia than when tested in aqueous suspension. B. cereus, a foodborne pathogen, proved to be markedly less sensitive to Oxonia under the described test conditions. The decreased sensitivity to Oxonia by the foodborne pathogen B. cereus raises concern about the efficacy of the sterilant for aseptic packaging of low-acid foods. Further work will be needed to determine if this decreased sensitivity is an inherent property of the organism that affords unusual protection against Oxonia or if the challenge parameters selected were at the minimum conditions for efficacy.