Impact of agglomeration on the quantitative assessment of Bacillus stearothermophilus heat inactivation

Mathys, Alexander; Heinz, Volker; Schwartz, Friedel Herbert; Knorr, Dietrich

doi:10.1016/j.jfoodeng.2006.11.012

Cited by 35 publications

(23 citation statements)

References 30 publications

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“…A similar effect has been described before, as a "shoulder formation" in the inactivation kinetics of HP-treated B. subtilis spores, a phenomenon that was assigned to spore agglomerates that disassociated during HP treatment (40,41). In the present study, we observed an increase in CFU per milliliter for three strains (Fig.…”

Section: Discussionsupporting

confidence: 89%

Effects of High Pressure on Bacillus licheniformis Spore Germination and Inactivation

Borch-Pedersen

Mellegård

Reineke

et al. 2017

Appl Environ Microbiol

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Bacillus and Clostridium species form spores, which pose a challenge to the food industry due to their ubiquitous nature and extreme resistance. Pressurization at Ͻ300 MPa triggers spore germination by activating germination receptors (GRs), while pressurization at Ͼ300 MPa likely triggers germination by opening dipicolinic acid (DPA) channels present in the inner membrane of the spores. In this work, we expose spores of Bacillus licheniformis, a species associated with food spoilage and occasionally with food poisoning, to high pressure (HP) for holding times of up to 2 h. By using mutant spores lacking one or several GRs, we dissect the roles of the GerA, Ynd, and GerK GRs in moderately HP (mHP; 150 MPa)-induced spore germination. We show that Ynd alone is sufficient for efficient mHPinduced spore germination. GerK also triggers germination with mHP, although at a reduced germination rate compared to that of Ynd. GerA stimulates mHP-induced germination but only in the presence of either the intact GerK or Ynd GR. These results suggests that the effectiveness of the individual GRs in mHP-induced germination differs from their effectiveness in nutrient-induced germination, where GerA plays an essential role. In contrast to Bacillus subtilis spores, treatment with very HP (vHP) of 550 MPa at 37°C did not promote effective germination of B. licheniformis spores. However, treatment with vHP in combination with elevated temperatures (60°C) gave a synergistic effect on spore germination and inactivation. Together, these results provide novel insights into how HP affects B. licheniformis spore germination and inactivation and the role of individual GRs in this process.IMPORTANCE Bacterial spores are inherently resistant to food-processing regimes, such as high-temperature short-time pasteurization, and may therefore compromise food durability and safety. The induction of spore germination facilitates subsequent inactivation by gentler processing conditions that maintain the sensory and nutritional qualities of the food. High-pressure (HP) processing is a nonthermal food-processing technology used to eliminate microbes from food. The application of this technology for spore eradication in the food industry requires a better understanding of how HP affects the spores of different bacterial species. The present study provides novel insights into how HP affects Bacillus licheniformis spores, a species associated with food spoilage and occasionally food poisoning. We describe the roles of different germination receptors in HPinduced germination and the effects of two different pressure levels on the germination and inactivation of spores. This study will potentially contribute to the effort to implement HP technology for spore inactivation in the food industry.KEYWORDS Bacillus licheniformis, spore germination, germination receptor, endospores, high pressure, high-pressure processing, spore inactivation, flow cytometry

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Section: Discussionsupporting

confidence: 89%

Effects of High Pressure on Bacillus licheniformis Spore Germination and Inactivation

Borch-Pedersen

Mellegård

Reineke

et al. 2017

Appl Environ Microbiol

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“…All relevant parameter and statistical results for the modelling are given in Table 1. In comparison with Mathys, Heinz, Schwartz, and Knorr (2007a), where the same inactivation method and strain was used, it can be seen that there is a lower resistance of G. stearothermophilus spores in this study. This effect resulted from the freezing at À80°C, which lowered the thermal resistance (high-pressure inactivation was not observed in Mathys et al, 2007a).…”

Section: Thermal Inactivationmentioning

confidence: 54%

“…Other authors (Keynan et al, 1964) assumed that heat or reducing agents change the tertiary structure of a protein responsible for the maintenance of the dormant state by reducing the disulfide linkages which stabilise the protein in a specific configuration. Another theory is given by Bueltermann (1997) and Mathys et al (2007a). The authors investigated the agglomeration behaviour of G. stearothermophilus spore suspensions and found that the lag phase often found in thermal spore inactivation (shoulder formation) can sufficiently be described by first-order inactivation kinetics when the agglomeration size is considered.…”

Section: Comparison Of Inactivation Difference Under Heat and Pressurementioning

confidence: 99%

“…Aiba and Toda (1966) used a probabilistic agglomeration approach for the calculation of spore clump life span distribution and Furukawa et al (2005) explained the non-linear tailing during heat treatment with the same relationship, but without detailed mathematical descriptions. The mentioned probabilistic agglomeration model and the work from Bueltermann (1997) and Mathys et al (2007a) have the same basic mathematical approach.…”

Section: Comparison Of Inactivation Difference Under Heat and Pressurementioning

confidence: 99%

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Impact of dissociation equilibrium shift on bacterial spore inactivation by heat and pressure

Mathys¹,

Kallmeyer²,

Heinz

et al. 2008

Food Control

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“…Furthermore, the come-up time (the time to reach the desired temperature) of capillary tubes that contain spore suspension to be tested for heat resistance is approximately 3 s at this temperature (25,26). This body of information therefore indicates that the presence of vegetative cells in a given suspension and/ or food sample does not affect the enumeration of spore survivors after exposure to 121…”

Section: )mentioning

confidence: 99%

Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock

Byun

Cho

Hwang

et al. 2011

Food Sci Biotechnol

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Impact of agglomeration on the quantitative assessment of Bacillus stearothermophilus heat inactivation

Cited by 35 publications

References 30 publications

Effects of High Pressure on Bacillus licheniformis Spore Germination and Inactivation

Effects of High Pressure on Bacillus licheniformis Spore Germination and Inactivation

Impact of dissociation equilibrium shift on bacterial spore inactivation by heat and pressure

Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock

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