title: Two distinct groups within the Bacillus subtilis group display significantly different spore heat resistance properties.
abstract: The survival of bacterial spores after heat treatment and the subsequent germination and outgrowth in a food product can lead to spoilage of the food product and economical losses. Prediction of time-temperature conditions that lead to sufficient inactivation requires access to detailed spore thermal inactivation kinetics of relevant model strains. In this study, the thermal inactivation kinetics of spores of fourteen strains belonging to the Bacillus subtilis group were determined in detail, using both batch heating in capillary tubes and continuous flow heating in a micro heater. The inactivation data were fitted using a log linear model. Based on the spore heat resistance data, two distinct groups (p < 0.001) within the B. subtilis group could be identified. One group of strains had spores with an average D120 °C of 0.33 s, while the spores of the other group displayed significantly higher heat resistances, with an average D120 °C of 45.7 s. When comparing spore inactivation data obtained using batch- and continuous flow heating, the z-values were significantly different, hence extrapolation from one system to the other was not justified. This study clearly shows that heat resistances of spores from different strains in the B. subtilis group can vary greatly. Strains can be separated into two groups, to which different spore heat inactivation kinetics apply.
authors.affiliation: Top Institute Food and Nutrition (TIFN), Nieuwe kanaal 9A, 6709 PA Wageningen, The Netherlands; University of Groningen, Laboratory of Molecular Genetics, Nijenborgh 7, 9747 AG Groningen, The Netherlands; NIZO Food Research B.V., Kernhemseweg 2, 6718 ZB Ede, The Netherlands.
authors.forename: Erwin M
authors.initials: EM
authors.lastname: Berendsen
authors.affiliation: Top Institute Food and Nutrition (TIFN), Nieuwe kanaal 9A, 6709 PA Wageningen, The Netherlands; Wageningen University, Laboratory of Food Microbiology, P.O. Box 17 6700 AA Wageningen, The Netherlands.
authors.forename: Marcel H
authors.initials: MH
authors.lastname: Zwietering
authors.affiliation: Top Institute Food and Nutrition (TIFN), Nieuwe kanaal 9A, 6709 PA Wageningen, The Netherlands; University of Groningen, Laboratory of Molecular Genetics, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Oscar P
authors.initials: OP
authors.lastname: Kuipers
authors.affiliation: Top Institute Food and Nutrition (TIFN), Nieuwe kanaal 9A, 6709 PA Wageningen, The Netherlands; NIZO Food Research B.V., Kernhemseweg 2, 6718 ZB Ede, The Netherlands. Electronic address: Marjon.Wells-Bennik@nizo.com.
authors.forename: Marjon H J
authors.initials: MH
authors.lastname: Wells-Bennik
mesh_terms: D001412:Bacillus subtilis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001483:Base Sequence; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005506:Food Contamination; D005516:Food Microbiology; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013171:Spores, Bacterial
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S
keywords: Bacillus subtilis group; Batch heating; Continuous flow heating; Spore inactivation; Strain variation