The Effect of Lysozyme on the Apparent Heat Resistance of Nonproteolytic Type B Clostridium Botulinum

Scott, Virginia N.; Bernard, Dane T.

doi:10.1111/j.1745-4565.1985.tb00537.x

Cited by 22 publications

(12 citation statements)

References 11 publications

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“…botulinum will depend on whether lysozyme (or egg-yolk) is included in the recovery medium, and whether D-values are based on a survival curve method or an endpoint method (e.g. Scott and Bernard 1985). With both methods the D-value will depend on whether it is estimated from a 2 log or 4-6 log heat-inactivation, in the former case the D-value may hardly be affected by the resistance of lysozyme permeable heated spores, whereas in the latter case it will be affected greatly.…”

Section: Discussionmentioning

confidence: 99%

Heat-resistance of spores of non-proteolytic Clostridium botulinum estimated on medium containing lysozyme

Peck

Fairbairn

Lund

1993

Lett Appl Microbiol

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Heat treatment of spores of non‐proteolytic strains of Clostridium botulinum at 75–90°C, and enumeration of survivors on a nutrient medium containing lysozyme gave biphasic survival curves. A majority of spores were inactivated rapidly by heating, and the apparent heat‐resistance of these spores was similar to that observed by enumeration on medium without lysozyme. A minority of spores showed much greater heat‐resistance, due to the fact that the spore coat was permeable to lysozyme, which diffused into the spore from the medium and replaced the heat‐inactivated germination system. The proportion of heated spores permeable to lysozyme was between 0.2 and 1.4% for spores of strains 17B (type B) and Beluga (type E), but was about 20% for spores of strain Foster B96 (type E). After treatment of heated spores with alkaline thioglycolate, all were permeable to lysozyme. D‐values for heated spores that were permeable to lysozyme (naturally and after treatment with thioglycolate) were: for strain 17B, D85°C, 100 min; D90°C, 18.7 min; D95°C, 4.4 min; for strain Beluga, D85°C, 46 min; D90°C, 11.8 min; D95°C, 2.8 min. The z‐values for these spores of strains 17B and Beluga were 7.6°C and 8.3°C.

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Section: Discussionmentioning

confidence: 99%

Heat-resistance of spores of non-proteolytic Clostridium botulinum estimated on medium containing lysozyme

Peck

Fairbairn

Lund

1993

Lett Appl Microbiol

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“…Tests in phosphate buffers have revealed 6 spores of C. botulinum type E strain Beluga in rainbow trout and whitefish media. }, growth observed in rainbow trout medium within 90 days at 30°C, {, no growth observed in rainbow trout medium; F, growth observed in whitefish medium within 90 days at 30°C, E, no growth observed in whitefish medium; ----, 6D heat treatments (i.e., heat treatments proposed to eliminate 10 6 nonproteolytic spores) recommended by the Advisory Committee on the Microbiological Safety of Foods (1); ------, 6D heat treatments recommended by the European Chilled Food Federation (17 (3), and 2.8 min at 95°C (37), as opposed to 0.07 to 6.6 min at 82°C without lysozyme (7,11,27,32,44,47). The heat-resistant spore fraction was estimated to be on the order of 0.1%, while in phosphate buffer percentages of 0.1 to 1.0% and sometimes up to 20% have been reported (37).…”

Section: Discussionmentioning

confidence: 99%

“…Biphasic survivor curves indicate that from 0.1 to 20% of a spore population is permeable to lysozyme and is more heat resistant than the nonpermeable fraction (37,45). Without the addition of lysozyme to the recovery medium, decimal reduction times (D values) for spores of type E strains of 0.07 to 6.6 min at 82°C, depending on the heating medium, have been reported (7,11,27,32,41,44,47); with lysozyme, higher D values of 48.3, 12.6, and 3.17 min at 85, 90, and 95°C, respectively, have been determined (37).…”

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confidence: 99%

Thermal Inactivation of Nonproteolytic Clostridium botulinum Type E Spores in Model Fish Media and in Vacuum-Packaged Hot-Smoked Fish Products

Lindström

Nevas

Hielm

et al. 2003

Appl Environ Microbiol

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Thermal inactivation of nonproteolytic Clostridium botulinum type E spores was investigated in rainbow trout and whitefish media at 75 to 93°C. Lysozyme was applied in the recovery of spores, yielding biphasic thermal destruction curves. Approximately 0.1% of the spores were permeable to lysozyme, showing an increased measured heat resistance. Decimal reduction times for the heat-resistant spore fraction in rainbow trout medium were 255, 98, and 4.2 min at 75, 85, and 93°C, respectively, and those in whitefish medium were 55 and 7.1 min at 81 and 90°C, respectively. The z values were 10.4°C in trout medium and 10.1°C in whitefish medium. Commercial hot-smoking processes employed in five Finnish fish-smoking companies provided reduction in the numbers of spores of nonproteolytic C. botulinum of less than 103 . An inoculated-pack study revealed that a time-temperature combination of 42 min at 85°C (fish surface temperature) with >70% relative humidity (RH) prevented growth from 10 6 spores in vacuum-packaged hot-smoked rainbow trout fillets and whole whitefish stored for 5 weeks at 8°C. In Finland it is recommended that hot-smoked fish be stored at or below 3°C, further extending product safety. However, heating whitefish for 44 min at 85°C with 10% RH resulted in growth and toxicity in 5 weeks at 8°C. Moist heat thus enhanced spore thermal inactivation and is essential to an effective process. The sensory qualities of safely processed and more lightly processed whitefish were similar, while differences between the sensory qualities of safely processed and lightly processes rainbow trout were observed.

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“…The apparent heat resistance of spores of non-proteolytic CI. botulinum can be increased considerably by the presence of lysozyme in the recovery medium (Scott and Bernard 1985;Peck et al 1992aPeck et al ,b, 1993. Lysozyme may be present in many foods (Lund and Peck 1994), and there is a lack of published evidence to show the effect of lysozyme in foods, on the processing and storage conditions required to inactivate spores of non-proteolytic CI.…”

Section: Introductionmentioning

confidence: 99%

Effect of Iysozyme concentration, heating at 90°C, and then incubation at chilled temperatures on growth from spores of non-proteolytic Clostridium botulinum

Peck

1995

Lett Appl Microbiol

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The heat treatment necessary to inactivate spores of non-proteolytic Clostridium botulinum in refrigerated, processed foods may be influenced by the occurrence of lysozyme in these foods. Spores of six strains of non-proteolytic Cl. botulinum were inoculated into tubes of an anaerobic meat medium, to give 10(6) spores per tube. Hen egg white lysozyme (0-50 micrograms ml-1 was added, and the tubes were given a heat treatment equivalent to 19.8 min at 90 degrees C, cooled, and incubated at 8 degrees, 12 degrees, 16 degrees and 25 degrees C for up to 93 d. In the absence of added lysozyme, neither growth nor toxin formation were observed. A 6-D inactivation was therefore achieved. In tubes to which lysozyme (5-50 micrograms ml-1 had been added prior to heating, growth and toxin formation were observed. With lysozyme added at 50 micrograms ml-1, growth was first observed after 68 d at 8 degrees C, 31 d at 12 degrees C, 24 d at 16 degrees C, and 9 d at 25 degrees C. Thus, in these circumstances, a heat treatment equivalent to 19.8 min at 90 degrees C was not sufficient, on its own, to give a 6-D inactivation. A combination of the heat treatment, maintenance at less than 12 degrees C, and a shelf-life not more than 4 weeks reduced the risk of growth of non-proteolytic Cl. botulinum by a factor of 10(6).

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The Effect of Lysozyme on the Apparent Heat Resistance of Nonproteolytic Type B Clostridium Botulinum

Cited by 22 publications

References 11 publications

Heat-resistance of spores of non-proteolytic Clostridium botulinum estimated on medium containing lysozyme

Heat-resistance of spores of non-proteolytic Clostridium botulinum estimated on medium containing lysozyme

Thermal Inactivation of Nonproteolytic Clostridium botulinum Type E Spores in Model Fish Media and in Vacuum-Packaged Hot-Smoked Fish Products

Effect of Iysozyme concentration, heating at 90°C, and then incubation at chilled temperatures on growth from spores of non-proteolytic Clostridium botulinum

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