Effect of Small, Acid-Soluble Proteins on Spore Resistance and Germination under a Combination of Pressure and Heat Treatment
Abstract:To find the range of pressure required for effective high-pressure inactivation of bacterial spores and to investigate the role of α/β-type small, acid-soluble proteins (SASP) in spores under pressure treatment, mild heat was combined with pressure (room temperature to 65°C and 100 to 500 MPa) and applied to wild-type and SASP-α−/β− Bacillus subtilis spores. On the one hand, more than 4 log units of wild-type spores were reduced after pressurization at 100 to 500 MPa and 65°C. On the other hand, the number of surviving mutant spores decreased by 2 log units at 100 MPa and by more than 5 log units at 500 MPa. At 500 MPa and 65°C, both wild-type and mutant spore survivor counts were reduced by 5 log units. Interestingly, pressures of 100, 200, and 300 MPa at 65°C inactivated wild-type SASP-α+/β+ spores more than mutant SASP-α−/β− spores, and this was attributed to less pressure-induced germination in SASP-α−/β− spores than in wild-type SASP-α+/β+ spores. However, there was no difference in the pressure resistance between SASP-α+/β+ and SASP-α−/β− spores at 100 MPa and ambient temperature (approximately 22°C) for 30 min. A combination of high pressure and high temperature is very effective for inducing spore germination, and then inactivation of the germinated spore occurs because of the heat treatment. This study showed that α/β-type SASP play a role in spore inactivation by increasing spore germination under 100 to 300 MPa at high temperature.
Document Type: Research Article
Affiliations: 1: Korea Food Research Institute, San 46-1, Baekhyun-dong, Bundang-gu, Seongnam-si, Kyunggi-do 463-420, Republic of Korea 2: Division of Food Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK 3: NCMH Laboratory, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK 4: School of Food Biosciences, University of Reading, P.O. Box 226, Whitenights, Reading, RG6 6BZ, UK
Publication date: September 1, 2007
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