Identification of bacteria in pasteurized zucchini purees stored at different temperatures and comparison with those found in other pasteurized vegetable purees

One hundred nineteen isolates from a commercial zucchini pure stored at 4, 10, and 20 to 25 degreesC were fingerprinted using repetitive sequence-based PCR (REP-PCR) and classified into 35 REP types. One representative isolate of each REP type was subsequently identified by API50CHB/20E profile and partial rrs gene sequence analysis. Nine REP types were misidentified by the API system. Strains were misidentified as being in the Bacillus circulans (group 2) API taxon or in taxa with a low number of positive API characters such as Brevibacillus brevis. A phylogenetic analysis pointed to one new species of Bacillus and three new species of Paenibacillus among the misidentified REP types. Bacterial components in zucchini puree were compared phenotypically with those obtained in previous work on broccoli, carrot, leek, potato, and split pea purees, based on simple matching coefficient and unweighted pair group method with averages cluster analysis. Out of 254 strains, 69 strains previously identified as B. circulans (group 2) or B. circulans/B. macerans/B. polymyxa were assigned to a new Paenibacillus taxon phylogenetically related to P. azotofixans. Storage conditions at 4 degreesC favored the development of B. macroides/B. maroccanus and Paenibacillus spp. in zucchini purees and Paenibacillus spp. in other purees. Storage conditions at 20 to 25 degreesC favored the development of B. subtilis group (B. licheniformis and B. subtilis) and B. cereus group strains. At 10 degreesC, Paenibacillus spp. were always present at high frequencies, whereas the occurrence of B. macroides/B. maroccanus (in zucchini purees), B. cercus, and B. pumilus varied with the experiment.