Optimization of pressure-induced germination of Bacillus sporothermodurans spores in water and milk.
2012
Aouadhi, C. | Simonin, Hélène | Prévost, H. | Lamballerie, M De | Maaroufi, A. | Mejri, S. | Institut Pasteur de Tunis ; Pasteur Network (Réseau International des Instituts Pasteur) | Laboratory of Animal Resources and Food Technology ; National Institute of Agronomy, Tunis (INAT) | Laboratoire de génie des procédés - environnement - agroalimentaire (GEPEA) ; Mines Nantes (Mines Nantes)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST) ; Université de Nantes (UN)-Université de Nantes (UN)-École nationale vétérinaire, agroalimentaire et de l'alimentation Nantes-Atlantique (ONIRIS)-Centre National de la Recherche Scientifique (CNRS) | SECurité des ALIments et Microbiologie (SECALIM) ; Institut National de la Recherche Agronomique (INRA)-École nationale vétérinaire, agroalimentaire et de l'alimentation Nantes-Atlantique (ONIRIS) | Tunisian Ministry of Higher Education and Scientific Research
Bacillus sporothermodurans produces highly resistant endospores that can survive ultra-high-temperature treatment in milk. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk sterility. In this work, the rate of spore germination of B. sporothermodurans LTIS27 was measured in distilled water after high-pressure treatments with varying pressure (50-600 MPa), treatment temperature (20-50 °C), pressure-holding time (5-30 min) and post-pressurization incubation time (30-120 min) at 37 °C or 4 °C. The results showed that pressure-induced germination was maximal (62%) after a treatment at 200 MPa and 20 °C and increased with pressure-holding time and post-pressurization incubation time. Treatment temperature had no significant effect on germination. A central composite experimental design with three factors (pressure, pressure-holding time, and post-pressurization incubation time) using response surface methodology was used to optimize the germination rate in distilled water and in skim milk. No factor interaction was observed. Germination was induced at lower pressure and was faster in milk than in distilled water, but complete germination was not reached. The optimum germination obtained with experimental data was 5.0 log cfu/mL in distilled water and 5.2 log cfu/mL in milk from 5.7 log cfu/mL of spores initially present in the suspension. This study shows the potential of using high hydrostatic pressure to induce the germination of B. sporothermodurans spores in milk before a heat treatment.
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