Predicting Thermophilic Spore Population Dynamics for UHT Sterilization Processes

Sapru, V.; Teixeira, Arthur A.; Smerage, Glen H.; Lindsay, James

doi:10.1111/j.1365-2621.1992.tb11310.x

Cited by 53 publications

(27 citation statements)

References 20 publications

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“…The difference between the two counts can then be considered the initial number of dormant spores (1,25), based on the assumption that all the dormant spores were viable at the beginning of the experiment. Estimates reached by this method indicate that dormant Bacillus stearothermophilus spores can outnumber the initially active ones by a factor as large as 10 to 14 (17,24); i.e., they can constitute 90 to 93% of the total. In light of this observation, and for the sake of simplicity, we shall assume that the survival curves reported by Sapru et al (24) would be close to those of the dormant spores had they been tested alone.…”

Section: Vol 76 2010mentioning

confidence: 99%

“…Activation/survival of B. stearothermophilus spores at 105 and 110°C described by the semicontinuous version of equation 7 (top) and the corresponding activation and mortality rate functions P a (t) and P m (t), respectively (bottom). The original data are from Sapru et al (24).…”

Section: Fig 11mentioning

confidence: 99%

“…This was done with a minimization program based on the Simplex algorithm especially written for the purpose in Mathematica. The initial number of dormant spores (32.7 ϫ 10 8 ) was taken from Sapru et al (24). (The set of suitable initial parameters estimates ["guessed values"] was found by matching the experimental data with a curve created by the model's equation with coefficients adjusted by moving sliders on the screen using Mathematica's Manipulate function.…”

Section: Vol 76 2010mentioning

confidence: 99%

“…The most publicized model of the simultaneous heat activation and inactivation of Bacillus spores in food is that proposed by Sapru et al (24,25), which is an improved version of models proposed earlier by Shull et al (29) and Rodriguez et al (23). All of these authors and others (1,17) assumed that the activation of dormant spores follows first-order kinetics and so does their inactivation before and after activation.…”

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confidence: 99%

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Evaluation of a Stochastic Inactivation Model for Heat-Activated Spores of Bacillus spp

Corradini

Normand

Eisenberg

et al. 2010

Appl Environ Microbiol

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Heat activates the dormant spores of certain Bacillus spp., which is reflected in the "activation shoulder" in their survival curves. At the same time, heat also inactivates the already active and just activated spores, as well as those still dormant. A stochastic model based on progressively changing probabilities of activation and inactivation can describe this phenomenon. The model is presented in a fully probabilistic discrete form for individual and small groups of spores and as a semicontinuous deterministic model for large spore populations. The same underlying algorithm applies to both isothermal and dynamic heat treatments. Its construction does not require the assumption of the activation and inactivation kinetics or knowledge of their biophysical and biochemical mechanisms. A simplified version of the semicontinuous model was used to simulate survival curves with the activation shoulder that are reminiscent of experimental curves reported in the literature. The model is not intended to replace current models to predict dynamic inactivation but only to offer a conceptual alternative to their interpretation. Nevertheless, by linking the survival curve's shape to probabilities of events at the individual spore level, the model explains, and can be used to simulate, the irregular activation and survival patterns of individual and small groups of spores, which might be involved in food poisoning and spoilage.Heat inactivation kinetics of bacterial spores is a wellresearched field. Much of the work on its relation to foods has focused on the heat-resistant spores of Clostridia, particularly those of Clostridium botulinum, which to this date serves as the reference organism in sterility calculations of low-acid foods (8, 32). The thermal resistance of Bacilli spores, although also extensively studied, has received less attention in the literature on food preservation. This is primarily because they are unlikely to germinate and produce cells that will survive and divide under the anaerobic conditions in a sterilized food container. Yet the mere possibility of viable Bacillus spores being present in processed foods has become an issue of food safety and a security concern. For this reason, there is a renewed interest in these spores' heat resistance (2,3,6,7,16,30). One of the peculiarities of certain Bacillus spores, like those of Bacillus sporothermodurans or Bacillus stearothermophilus, is that many of them can remain dormant unless activated by heat. The result is a survival curve that exhibits an "activation shoulder," as shown schematically in Fig. 1 and with published data in Fig. 2. Thus, modeling this survival pattern, where the number of spores initially grows rather than declines, must account for the heat's dual role of being a lethal agent and activator at the same time.Traditionally, the thermal inactivation of both Clostridia and Bacilli spores has been thought to follow first-order kinetics (9, 12, 31), an assumption that has been frequently challenged in recent years (18,21,33,35). The most p...

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Section: Vol 76 2010mentioning

confidence: 99%

Section: Fig 11mentioning

confidence: 99%

Section: Vol 76 2010mentioning

confidence: 99%

mentioning

confidence: 99%

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Evaluation of a Stochastic Inactivation Model for Heat-Activated Spores of Bacillus spp

Corradini

Normand

Eisenberg

et al. 2010

Appl Environ Microbiol

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“…To adjust to those behaviors more sophisticated models have been proposed (Peleg and Penchina, 2000;Sapru et al, 1992). Some of them combine first-order kinetics for distinct microbial inactivation stages, while others use probability models.…”

Section: General Considerations On Thermobacteriologymentioning

confidence: 99%

Scientific Opinion on Hatchery Waste as animal by‐products

Andréoletti¹,

Budka²,

Bunčić³

et al. 2011

EFS2

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The risk posed by the possible use of dead-in-shell chicks for the production of processed petfood was assessed. According to current legislation two processing methods were considered i) treatment to a minimum Fc value of 3; and ii) treatment of at least 90°C throughout the substance of the final product. A list of the possible pathogens potentially present in the material to be treated was compiled and the available literature data was used to assess the ability of the processing methods to inactivate the most resistant pathogens identified. The processing methods were assessed assuming that the heat treatments would be performed in a moist environment. Spores of Clostridium botulinum were identified as the most resistant hazard potentially present in the material to be processed. Circovirus and parvovirus, and Enterococcus faecium were considered respectively as the most resistant viruses and non-sporulating bacterium to heat treatment. Moreover, depending on storage conditions, the generation of bacterial toxins could be possible. Consequently, the processing methods considered were assessed against their ability to inactivate those hazards. The risk related to the use of dead-in-shell chicks, submitted to a conventional heat treatment to a minimum Fc value of 3 in a moist environment, for the production of canned petfood was considered negligible. No indication is given in the current regulation on the processing time and heating method needed for the treatment at 90°C throughout the substance of the final product. A treatment lasting 18 seconds can assure a rapid destruction of the non-sporeforming bacteria identified as hazards. However, this treatment is not able to inactivate other relevant hazards such as bacterial spores, thermoresistant viruses and some toxins. The final risk posed by the agents that may survive this treatment additionally depends on several factors and cannot be considered to be negligible.

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Dense Phase Carbon Dioxide

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Predicting Thermophilic Spore Population Dynamics for UHT Sterilization Processes

Cited by 53 publications

References 20 publications

Evaluation of a Stochastic Inactivation Model for Heat-Activated Spores of Bacillus spp

Evaluation of a Stochastic Inactivation Model for Heat-Activated Spores of Bacillus spp

Scientific Opinion on Hatchery Waste as animal by‐products

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