Frédéric Carlin - Academia.edu (original) (raw)

Papers by Frédéric Carlin

FEMS Microbiology Reviews

The environment in which spores of Bacillus sp form shapes spore properties and capacities of res... more The environment in which spores of Bacillus sp form shapes spore properties and capacities of resistance, germination and further growth.

Applied and Environmental Microbiology

Bacterial adaptation is characterized by a lag-phase during which cells do not multiply and modif... more Bacterial adaptation is characterized by a lag-phase during which cells do not multiply and modify their physiology to cope with the constraints of their environment. Our aim was to determine a sequence of events during the lag-phase of growth at low temperature and pH for three Bacillus cereus strains. The onsets of expression of two genes, essential for stress adaptation (cshA coding for a RNA helicase) or involved in the transition between lag and exponential phase (abrB coding for a transition regulator), were determined using fluorescent transcriptional reporter systems. Regardless of the stressing conditions and the tested strains, cshA promoter was active very early, while the biomass increased and always before the first cell division. At 12°C and pH 7.0, onset of cshA promoter activity occurred between 3 h and 7 h, while bacterial counts started between 12 h and 13 h. At pH 5.0 and at 20°C or 30°C, onset of cshA promoter activity occurred before 1 h and earlier than at pH 7...

Research in Microbiology, 2016

The Science of the total environment, Aug 22, 2016

Fresh produce has been a growing cause of food borne outbreaks world-wide prompting the need for ... more Fresh produce has been a growing cause of food borne outbreaks world-wide prompting the need for safer production practices. Yet fresh produce agrifood systems are diverse and under constraints for more sustainability. We analyze how measures taken to guarantee safety interact with other objectives for sustainability, in light of the diversity of fresh produce agrifood systems. The review is based on the publications at the interface between fresh produce safety and sustainability, with sustainability defined by low environmental impacts, food and nutrition security and healthy life. The paths for more sustainable fresh produce are diverse. They include an increased use of ecosystem services to e.g. favor predators of pests, or to reduce impact of floods, to reduce soil erosion, or to purify run-off waters. In contrast, they also include production systems isolated from the environment. From a socio-economical view, sustainability may imply maintaining small tenures with a higher ri...

Photochemistry and Photobiology, 2016

The resistance to pulsed light (PL) of spores of B. subtilis strain 168 and of strains with mutat... more The resistance to pulsed light (PL) of spores of B. subtilis strain 168 and of strains with mutations increasing sensitivity to UV-C or affecting spore structure was evaluated and compared to resistance to continuous UV-C and moist heat, in order to reveal original mechanisms of inactivation by PL. Spores of B. subtilis strain 168 (1A1) and nine mutant strains (sspA, sspB, sspAB, cotA, gerE, cotE, spl1, uvrA and recA) were exposed to PL (up to 1.77 J.cm(-2) ), continuous UV-C (up to 147 mJ.cm(-) ²) and moist-heat at 90°C. Spores of the strains lacking proteins linked to coat formation or structure (cotA, gerE and cotE) were markedly more sensitive to PL than 1A1, while their sensitivity to continuous UV-C or to moist-heat was similar to the one of strain 1A1. Coat proteins had a major contribution to the resistance of B. subtilis spores to PL irradiation characterized by short-time and high energy pulses of white light in the wavelengths 200 nm to 1100 nm. In contrast the role of coat proteins to UV-C or to moist-heat resistance was marginal or null. This article is protected by copyright. All rights reserved.

LWT - Food Science and Technology, 2016

Applied and environmental microbiology, Jan 23, 2015

The Bacillus cereus spore surface layers consist of a coat surrounded by an exosporium. We invest... more The Bacillus cereus spore surface layers consist of a coat surrounded by an exosporium. We investigated the interplay between the sporulation temperature and the CotE morphogenetic protein in the assembly of the surface layers of B. cereus ATCC14579 spores and on the resulting spore properties. The cotE deletion affects the coat and exosporium composition of the spores formed at both the suboptimal temperature of 20°C and at the optimal growth temperature of 37°C. Transmission electron microscopy revealed that ΔcotE spores had a fragmented and detached exosporium when formed at 37°C. However, when produced at 20°C, ΔcotE spores showed defects in both coat and exosporium attachment, and were susceptible to lysozyme and mutanolysin. Thus, CotE has a role in the assembly of both the coat and exosporium, more important during sporulation at 20°C. CotE was more represented in extracts from spores formed at 20°C, suggesting that increased synthesis of the protein is required to maintain p...

Food Research International, 2015

Fermentation can contribute to improve functional aspects of foods. The first goal of this study ... more Fermentation can contribute to improve functional aspects of foods. The first goal of this study was to determine amongst apple, grape and orange juices, the one with the best bacterial growth performance during fermentation by Lactobacillus strains from commercial and artisanal food origins, at 40°C for 48 h. The juice with the highest bacterial growth was evaluated for bacteria viability during 4 weeks of cold storage, superoxide dismutase (SOD) activity and folates production analyzed through HPLC/fluorimetry. Acceptability of fermented juice was appraised through hedonic analysis. Lactobacilli counts were the highest in apple and the lowest in orange juices at t = 48 h. In most cases, bacteria counts were higher in fermented (5.5 to 9.5 log CFU/ml) than in supplemented apple juices (4.2 to 5.7 log CFU/ml), at the 4th week of cold storage. SOD activity was significantly increased in all apple juices fermented by commercial Lactobacilli strains. Folates were produced in apple juices fermented by Lactobacillus plantarum and Lactobacillus rhamnosus. Apple juice was the best substrate for Lactobacillus growth and, considering bacterial viability and overall acceptance by the panelists, Lactobacillus acidophilus L10 was the most suitable strain for apple juice fermentation.

Food Research International, 2015

Hydrosols are hydrodistillation products of aromatic plants. They contain less than 1g/L of dispe... more Hydrosols are hydrodistillation products of aromatic plants. They contain less than 1g/L of dispersed essential oils giving organoleptic properties. Hydrosols are subjected to microbial proliferation. Reasons for spoilage have to be found in the nature of substrates supporting growth and of microbiological contaminants. The composition in essential oils and the microbiota of 22 hydrosol samples of Citrus aurantium L. ssp. amara L. (orange blossom), Rosa damascena Miller (rose D.), and Rosa centifolia L. (rose C.) flowers were analyzed to determine the factors responsible for decay. The median concentrations in essential oils were 677mg/L for orange blossom hydrosols, 205mg/L for rose D. hydrosols, and 116mg/L for rose C. hydrosols. The dry matter content of these hydrosols varied between 4.0mg/L and 702mg/L, and the carbohydrate content varied between 0.21mg/L and 0.38mg/L. These non-volatile compounds were likely carried over during distillation by a priming and foaming effect, and could be used as nutrients by microorganisms. A microbial proliferation at ambient temperature and also at 5°C has been observed in all studied hydrosols when stored in a non-sterile container. In contaminated hydrosols, maximal counts were about 7log10CFU/mL, while the French pharmacopeia recommends a maximal total bacterial count of 2log10CFU/mL. Neither yeast nor mold was detected. The isolated microbial population was composed of environmental Gram-negative bacteria, arranged in four major genera: Pseudomonas sp., Burkholderia cepacia complex, and presumably two new genera belonging to Acetobacteraceae and Rhodospirillaceae. Among those bacteria, Burkholderia vietnamiensis and Novosphingobium capsulatum were able to metabolize volatile compounds, such as geraniol to produce 6-methyl-5-hepten-2-one or geranic acid, or phenylethyl acetate to produce 2-phenylethanol. EO concentrations in hydrosols or cold storage are not sufficient to insure microbiological stability. Additional hurdles such as chemical preservatives or aseptic packaging will be necessary to insure microbial stability.

Photochemistry and photobiology

The photoprotective potential of fungus pigments was investigated by irradiating conidiospores of... more The photoprotective potential of fungus pigments was investigated by irradiating conidiospores of three Aspergillus niger strains possessing the same genetic background, but differing in their degree of pigmentation with pulsed light (PL) and monochromatic (254 nm) UV-C radiation. Spores of A. niger MA93.1 and JHP1.1 presenting, respectively, a fawn and a white pigmentation were more sensitive to PL and continuous UV-C radiation than the wild-type A. niger strain N402 possessing a dark pigment. Both spores of the dark A. niger N402 and the fawn-color mutant were equally resistant to moist heat at 56°C while spores of the white-color mutant were highly sensitive. These results indicate that melanin protects pigmented spores of A. niger from PL.

International Journal of Food Microbiology, 2015

Journal of food protection, 2001

A molecular method was used for the detection of Clostridium botulinum spores of type A, B, and E... more A molecular method was used for the detection of Clostridium botulinum spores of type A, B, and E in commercial cooked and pasteurized vegetable purées and in the raw materials (vegetables and other ingredients). The method allowed the detection of less than 8 spores/g of product for C. botulinum type A, less than 1 spore/g for proteolytic type B, less than 21 spores/g for nonproteolytic type B, and less than 0.1 spore/g for type E. Thirty-seven samples of raw vegetables and ingredients were tested for the presence of C. botulinum type A, B, and E; 88 and 90 samples of vegetable purées were tested, respectively, for the presence of C. botulinum type A and B and for the presence of C. botulinum type E. All samples were negative, suggesting that the prevalence of C. botulinum in these vegetable purées and the raw ingredients is probably low.

Journal of food protection, 2001

Four Enterobacteriaceae (Enterobacter agglomerans and Rhanella aquatilis) and six pseudomonads (P... more Four Enterobacteriaceae (Enterobacter agglomerans and Rhanella aquatilis) and six pseudomonads (Pseudomonas fluorescens, Pseudomonas chlororaphis, Pseudomonas putida) isolated from minimally processed green endive were coinoculated at 10 degrees C with Listeria monocytogenes in a minimal medium. Pseudomonads did not modify the growth of L. monocytogenes, whereas Enterobacteriaceae reduced its maximal population by 2 to 3 log CFU/ml. The same effect was observed in a diluted yeast extract medium supplemented with amino acids and glucose, in which L. monocytogenes grown alone reached 10(9) to 10(10) CFU/ml. In the same diluted yeast extract medium, not supplemented with glucose and amino acids, the maximal population of L. monocytogenes in the presence of both Enterobacteriaceae and pseudomonads was only slightly reduced (less than 0.5 log CFU/ml). Culture filtrates of the Enterobacteriaceae had no inhibitory activity on L. monocytogenes. The effect of the Enterobacteriaceae on L. mon...

Journal of food protection, 2002

The saprophytic Paenibacillus and Bacillus spp. found in cooked chilled foods may have an effect ... more The saprophytic Paenibacillus and Bacillus spp. found in cooked chilled foods may have an effect on the growth of Clostridium botulinum, a major microbiological hazard, especially for pasteurized vacuum-packaged products. Culture supernatants of 200 strains of Paenibacillus and Bacillus strains isolated from commercial cooked chilled foods containing vegetables were screened for activity against C. botulinum type A, proteolytic type B, and type E strains in a well diffusion assay. Nineteen strains were positive against C. botulinum. Among those, seven Paenibacillus polymyxa strains showed the highest antibotulinal activity and the largest antimicrobial spectrum against C. botulinum strains. The antibotulinal activity was evaluated throughout the growth of a representative strain of the positive P. polymyxa strains. The antimicrobial activity was detected in the culture supernatant from late-log/early stationary phase of the bacteria, which occurred after 7 to 10 days of incubation a...

Journal of food protection, 2003

The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in... more The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in mushroom, broccoli, and potato purées were monitored. Four strains of proteolytic C. botulinum types A and B were inoculated separately at approximately 10(4) spores per ml in nutrient broth and vegetable purées incubated at 15, 20, and 30 degrees C for up to 52 days. The times for the cell populations to increase 1,000-fold (T1,000) in the tested vegetables (1 to 5 days at 30 degrees C, 3 to 16 days at 20 degrees C, 7 to > 52 days at 15 degrees C) were similar to those for meat or fish. Only temperature significantly influenced growth rate. In contrast, the lag phase depended on the strains and media tested, in addition to temperature. Lag times and T1,000S for proteolytic C. botulinum were longer for potato and broccoli purées than for mushroom purée. These differences were not related to different pHs or redox potentials. The germination level, evaluated as the decrease in the spo...

Applied and Environmental Microbiology, 2014

ABSTRACTThe apparent heat resistance of spores ofBacillus weihenstephanensisandBacillus lichenifo... more ABSTRACTThe apparent heat resistance of spores ofBacillus weihenstephanensisandBacillus licheniformiswas measured and expressed as the time to first decimal reduction (δ value) at a given recovery temperature and pH. Spores ofB. weihenstephanensiswere produced at 30°C and 12°C, and spores ofB. licheniformiswere produced at 45°C and 20°C.B. weihenstephanensisspores were then heat treated at 85°C, 90°C, and 95°C, andB. licheniformisspores were heat treated at 95°C, 100°C, and 105°C. Heat-treated spores were grown on nutrient agar at a range of temperatures (4°C to 40°C forB. weihenstephanensisand 15°C to 60°C forB. licheniformis) or a range of pHs (between pH 4.5 and pH 9.5 for both strains). The recovery temperature had a slight effect on the apparent heat resistance, except very near recovery boundaries. In contrast, a decrease in the recovery pH had a progressive impact on apparent heat resistance. A model describing the heat resistance and the ability to recover according to the s...

Encyclopedia of Food Microbiology, 1999

FEMS Microbiology Reviews

The environment in which spores of Bacillus sp form shapes spore properties and capacities of res... more The environment in which spores of Bacillus sp form shapes spore properties and capacities of resistance, germination and further growth.

Applied and Environmental Microbiology

Bacterial adaptation is characterized by a lag-phase during which cells do not multiply and modif... more Bacterial adaptation is characterized by a lag-phase during which cells do not multiply and modify their physiology to cope with the constraints of their environment. Our aim was to determine a sequence of events during the lag-phase of growth at low temperature and pH for three Bacillus cereus strains. The onsets of expression of two genes, essential for stress adaptation (cshA coding for a RNA helicase) or involved in the transition between lag and exponential phase (abrB coding for a transition regulator), were determined using fluorescent transcriptional reporter systems. Regardless of the stressing conditions and the tested strains, cshA promoter was active very early, while the biomass increased and always before the first cell division. At 12°C and pH 7.0, onset of cshA promoter activity occurred between 3 h and 7 h, while bacterial counts started between 12 h and 13 h. At pH 5.0 and at 20°C or 30°C, onset of cshA promoter activity occurred before 1 h and earlier than at pH 7...

Research in Microbiology, 2016

The Science of the total environment, Aug 22, 2016

Fresh produce has been a growing cause of food borne outbreaks world-wide prompting the need for ... more Fresh produce has been a growing cause of food borne outbreaks world-wide prompting the need for safer production practices. Yet fresh produce agrifood systems are diverse and under constraints for more sustainability. We analyze how measures taken to guarantee safety interact with other objectives for sustainability, in light of the diversity of fresh produce agrifood systems. The review is based on the publications at the interface between fresh produce safety and sustainability, with sustainability defined by low environmental impacts, food and nutrition security and healthy life. The paths for more sustainable fresh produce are diverse. They include an increased use of ecosystem services to e.g. favor predators of pests, or to reduce impact of floods, to reduce soil erosion, or to purify run-off waters. In contrast, they also include production systems isolated from the environment. From a socio-economical view, sustainability may imply maintaining small tenures with a higher ri...

Photochemistry and Photobiology, 2016

The resistance to pulsed light (PL) of spores of B. subtilis strain 168 and of strains with mutat... more The resistance to pulsed light (PL) of spores of B. subtilis strain 168 and of strains with mutations increasing sensitivity to UV-C or affecting spore structure was evaluated and compared to resistance to continuous UV-C and moist heat, in order to reveal original mechanisms of inactivation by PL. Spores of B. subtilis strain 168 (1A1) and nine mutant strains (sspA, sspB, sspAB, cotA, gerE, cotE, spl1, uvrA and recA) were exposed to PL (up to 1.77 J.cm(-2) ), continuous UV-C (up to 147 mJ.cm(-) ²) and moist-heat at 90°C. Spores of the strains lacking proteins linked to coat formation or structure (cotA, gerE and cotE) were markedly more sensitive to PL than 1A1, while their sensitivity to continuous UV-C or to moist-heat was similar to the one of strain 1A1. Coat proteins had a major contribution to the resistance of B. subtilis spores to PL irradiation characterized by short-time and high energy pulses of white light in the wavelengths 200 nm to 1100 nm. In contrast the role of coat proteins to UV-C or to moist-heat resistance was marginal or null. This article is protected by copyright. All rights reserved.

LWT - Food Science and Technology, 2016

Applied and environmental microbiology, Jan 23, 2015

The Bacillus cereus spore surface layers consist of a coat surrounded by an exosporium. We invest... more The Bacillus cereus spore surface layers consist of a coat surrounded by an exosporium. We investigated the interplay between the sporulation temperature and the CotE morphogenetic protein in the assembly of the surface layers of B. cereus ATCC14579 spores and on the resulting spore properties. The cotE deletion affects the coat and exosporium composition of the spores formed at both the suboptimal temperature of 20°C and at the optimal growth temperature of 37°C. Transmission electron microscopy revealed that ΔcotE spores had a fragmented and detached exosporium when formed at 37°C. However, when produced at 20°C, ΔcotE spores showed defects in both coat and exosporium attachment, and were susceptible to lysozyme and mutanolysin. Thus, CotE has a role in the assembly of both the coat and exosporium, more important during sporulation at 20°C. CotE was more represented in extracts from spores formed at 20°C, suggesting that increased synthesis of the protein is required to maintain p...

Food Research International, 2015

Fermentation can contribute to improve functional aspects of foods. The first goal of this study ... more Fermentation can contribute to improve functional aspects of foods. The first goal of this study was to determine amongst apple, grape and orange juices, the one with the best bacterial growth performance during fermentation by Lactobacillus strains from commercial and artisanal food origins, at 40°C for 48 h. The juice with the highest bacterial growth was evaluated for bacteria viability during 4 weeks of cold storage, superoxide dismutase (SOD) activity and folates production analyzed through HPLC/fluorimetry. Acceptability of fermented juice was appraised through hedonic analysis. Lactobacilli counts were the highest in apple and the lowest in orange juices at t = 48 h. In most cases, bacteria counts were higher in fermented (5.5 to 9.5 log CFU/ml) than in supplemented apple juices (4.2 to 5.7 log CFU/ml), at the 4th week of cold storage. SOD activity was significantly increased in all apple juices fermented by commercial Lactobacilli strains. Folates were produced in apple juices fermented by Lactobacillus plantarum and Lactobacillus rhamnosus. Apple juice was the best substrate for Lactobacillus growth and, considering bacterial viability and overall acceptance by the panelists, Lactobacillus acidophilus L10 was the most suitable strain for apple juice fermentation.

Food Research International, 2015

Hydrosols are hydrodistillation products of aromatic plants. They contain less than 1g/L of dispe... more Hydrosols are hydrodistillation products of aromatic plants. They contain less than 1g/L of dispersed essential oils giving organoleptic properties. Hydrosols are subjected to microbial proliferation. Reasons for spoilage have to be found in the nature of substrates supporting growth and of microbiological contaminants. The composition in essential oils and the microbiota of 22 hydrosol samples of Citrus aurantium L. ssp. amara L. (orange blossom), Rosa damascena Miller (rose D.), and Rosa centifolia L. (rose C.) flowers were analyzed to determine the factors responsible for decay. The median concentrations in essential oils were 677mg/L for orange blossom hydrosols, 205mg/L for rose D. hydrosols, and 116mg/L for rose C. hydrosols. The dry matter content of these hydrosols varied between 4.0mg/L and 702mg/L, and the carbohydrate content varied between 0.21mg/L and 0.38mg/L. These non-volatile compounds were likely carried over during distillation by a priming and foaming effect, and could be used as nutrients by microorganisms. A microbial proliferation at ambient temperature and also at 5°C has been observed in all studied hydrosols when stored in a non-sterile container. In contaminated hydrosols, maximal counts were about 7log10CFU/mL, while the French pharmacopeia recommends a maximal total bacterial count of 2log10CFU/mL. Neither yeast nor mold was detected. The isolated microbial population was composed of environmental Gram-negative bacteria, arranged in four major genera: Pseudomonas sp., Burkholderia cepacia complex, and presumably two new genera belonging to Acetobacteraceae and Rhodospirillaceae. Among those bacteria, Burkholderia vietnamiensis and Novosphingobium capsulatum were able to metabolize volatile compounds, such as geraniol to produce 6-methyl-5-hepten-2-one or geranic acid, or phenylethyl acetate to produce 2-phenylethanol. EO concentrations in hydrosols or cold storage are not sufficient to insure microbiological stability. Additional hurdles such as chemical preservatives or aseptic packaging will be necessary to insure microbial stability.

Photochemistry and photobiology

The photoprotective potential of fungus pigments was investigated by irradiating conidiospores of... more The photoprotective potential of fungus pigments was investigated by irradiating conidiospores of three Aspergillus niger strains possessing the same genetic background, but differing in their degree of pigmentation with pulsed light (PL) and monochromatic (254 nm) UV-C radiation. Spores of A. niger MA93.1 and JHP1.1 presenting, respectively, a fawn and a white pigmentation were more sensitive to PL and continuous UV-C radiation than the wild-type A. niger strain N402 possessing a dark pigment. Both spores of the dark A. niger N402 and the fawn-color mutant were equally resistant to moist heat at 56°C while spores of the white-color mutant were highly sensitive. These results indicate that melanin protects pigmented spores of A. niger from PL.

International Journal of Food Microbiology, 2015

Journal of food protection, 2001

A molecular method was used for the detection of Clostridium botulinum spores of type A, B, and E... more A molecular method was used for the detection of Clostridium botulinum spores of type A, B, and E in commercial cooked and pasteurized vegetable purées and in the raw materials (vegetables and other ingredients). The method allowed the detection of less than 8 spores/g of product for C. botulinum type A, less than 1 spore/g for proteolytic type B, less than 21 spores/g for nonproteolytic type B, and less than 0.1 spore/g for type E. Thirty-seven samples of raw vegetables and ingredients were tested for the presence of C. botulinum type A, B, and E; 88 and 90 samples of vegetable purées were tested, respectively, for the presence of C. botulinum type A and B and for the presence of C. botulinum type E. All samples were negative, suggesting that the prevalence of C. botulinum in these vegetable purées and the raw ingredients is probably low.

Journal of food protection, 2001

Four Enterobacteriaceae (Enterobacter agglomerans and Rhanella aquatilis) and six pseudomonads (P... more Four Enterobacteriaceae (Enterobacter agglomerans and Rhanella aquatilis) and six pseudomonads (Pseudomonas fluorescens, Pseudomonas chlororaphis, Pseudomonas putida) isolated from minimally processed green endive were coinoculated at 10 degrees C with Listeria monocytogenes in a minimal medium. Pseudomonads did not modify the growth of L. monocytogenes, whereas Enterobacteriaceae reduced its maximal population by 2 to 3 log CFU/ml. The same effect was observed in a diluted yeast extract medium supplemented with amino acids and glucose, in which L. monocytogenes grown alone reached 10(9) to 10(10) CFU/ml. In the same diluted yeast extract medium, not supplemented with glucose and amino acids, the maximal population of L. monocytogenes in the presence of both Enterobacteriaceae and pseudomonads was only slightly reduced (less than 0.5 log CFU/ml). Culture filtrates of the Enterobacteriaceae had no inhibitory activity on L. monocytogenes. The effect of the Enterobacteriaceae on L. mon...

Journal of food protection, 2002

The saprophytic Paenibacillus and Bacillus spp. found in cooked chilled foods may have an effect ... more The saprophytic Paenibacillus and Bacillus spp. found in cooked chilled foods may have an effect on the growth of Clostridium botulinum, a major microbiological hazard, especially for pasteurized vacuum-packaged products. Culture supernatants of 200 strains of Paenibacillus and Bacillus strains isolated from commercial cooked chilled foods containing vegetables were screened for activity against C. botulinum type A, proteolytic type B, and type E strains in a well diffusion assay. Nineteen strains were positive against C. botulinum. Among those, seven Paenibacillus polymyxa strains showed the highest antibotulinal activity and the largest antimicrobial spectrum against C. botulinum strains. The antibotulinal activity was evaluated throughout the growth of a representative strain of the positive P. polymyxa strains. The antimicrobial activity was detected in the culture supernatant from late-log/early stationary phase of the bacteria, which occurred after 7 to 10 days of incubation a...

Journal of food protection, 2003

The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in... more The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in mushroom, broccoli, and potato purées were monitored. Four strains of proteolytic C. botulinum types A and B were inoculated separately at approximately 10(4) spores per ml in nutrient broth and vegetable purées incubated at 15, 20, and 30 degrees C for up to 52 days. The times for the cell populations to increase 1,000-fold (T1,000) in the tested vegetables (1 to 5 days at 30 degrees C, 3 to 16 days at 20 degrees C, 7 to > 52 days at 15 degrees C) were similar to those for meat or fish. Only temperature significantly influenced growth rate. In contrast, the lag phase depended on the strains and media tested, in addition to temperature. Lag times and T1,000S for proteolytic C. botulinum were longer for potato and broccoli purées than for mushroom purée. These differences were not related to different pHs or redox potentials. The germination level, evaluated as the decrease in the spo...

Applied and Environmental Microbiology, 2014

ABSTRACTThe apparent heat resistance of spores ofBacillus weihenstephanensisandBacillus lichenifo... more ABSTRACTThe apparent heat resistance of spores ofBacillus weihenstephanensisandBacillus licheniformiswas measured and expressed as the time to first decimal reduction (δ value) at a given recovery temperature and pH. Spores ofB. weihenstephanensiswere produced at 30°C and 12°C, and spores ofB. licheniformiswere produced at 45°C and 20°C.B. weihenstephanensisspores were then heat treated at 85°C, 90°C, and 95°C, andB. licheniformisspores were heat treated at 95°C, 100°C, and 105°C. Heat-treated spores were grown on nutrient agar at a range of temperatures (4°C to 40°C forB. weihenstephanensisand 15°C to 60°C forB. licheniformis) or a range of pHs (between pH 4.5 and pH 9.5 for both strains). The recovery temperature had a slight effect on the apparent heat resistance, except very near recovery boundaries. In contrast, a decrease in the recovery pH had a progressive impact on apparent heat resistance. A model describing the heat resistance and the ability to recover according to the s...

Encyclopedia of Food Microbiology, 1999