九州大学大学院生物資源環境科学府生物機能科学専攻食品バイオ工学講座食品衛生化学研究室 | 明治乳業(株)研究本部食品開発研究所
Laboratory of Food Hygienic Chemistry, Division of Food Biotechnology, Department of Bioscience and Biotechnology, Graduate School of BIoresource and Bioenvironmental Sciences, Kyushu University
Some strains of Bacillus spp/ isolated from dairy products grew at 10℃. The D-value at 100℃ of the spores of psychrotrophic Bacillus strains ranged from 1.1 to 3.2 min, suggesting that the spores of psychrotrophic Bacillus are killed by UHT heating at 120 to 130℃ for 2 sec. B. licheniformis strains isolates from raw milk and powered milk did not grow at 10℃. The components of sporulation media affected the resistance of B. subtils, B. cereus and B. licheniformis spores to sodium hypochlorite(NaClO). Only B.licheniformis spores formed by the cultivation on the nutrient agar supplemented with 0.1% CaCl2 largely increased the resistance against NaClO. B.cereus and B. subtlis spores formed on AKagar showed high resistance against NaClO. The resistance of cation-exchanged spores against NaClO was dependent on the kinds of exchanged divalent cation. The Ca and Mg ion treatments increased the resistance of B. subtlis and B. licheniformis spores against NaClO, respectively. Conversion of spores of B.licheniformis, B.cereus and B.subtilis to Mn-spore, especially in B.cereus spores, resulted in the decrease of theresistance against NaClO.. The resistance of B. subtlis spores against NaClO was decreased by the prologed incubation (17 days) for sporulation. The sporicidal effect of low-acidic electrolyzed oxidizing water (LAEW, ph5.5~6.5) with 20 ppm of available chlorine (A.C.) on spores of B. licheniformis, B.cereus and B. subtlis was higher than that of 100 ppm NaClO. B. cereus spores were most susceptible to LAEW. The B. cereus spores reduced viability by 1.35 log CFU/ml and >5.86 log CFU/ml after LAEW treatment for 4 min at 40 and 50℃, respectively. The sporicidal activity of LAEW to B. subtlis spores decreased drastically at pH higher than 7.0 and in the presence of 0.06% milk solid materials. Hypochlorous acid (HClO) in LAEW seemed to be a main factor for the sporicidal action of LAEW.
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