scholarly journals Development of a Log-Quadratic Model To Describe Microbial Inactivation, Illustrated by Thermal Inactivation of Clostridium botulinum

2009 ◽  
Vol 75 (22) ◽  
pp. 6998-7005 ◽  
Author(s):  
G. Stone ◽  
B. Chapman ◽  
D. Lovell
Keyword(s):  
Linear Model ◽  
Clostridium Botulinum ◽  
Thermal Inactivation ◽  
Microbial Inactivation ◽  
Quadratic Model ◽  
Inactivation Kinetics ◽  
Mathematical Framework ◽  
Model Framework ◽  
Weibull Models ◽  
Log Linear

ABSTRACT In the commercial food industry, demonstration of microbiological safety and thermal process equivalence often involves a mathematical framework that assumes log-linear inactivation kinetics and invokes concepts of decimal reduction time (DT ), z values, and accumulated lethality. However, many microbes, particularly spores, exhibit inactivation kinetics that are not log linear. This has led to alternative modeling approaches, such as the biphasic and Weibull models, that relax strong log-linear assumptions. Using a statistical framework, we developed a novel log-quadratic model, which approximates the biphasic and Weibull models and provides additional physiological interpretability. As a statistical linear model, the log-quadratic model is relatively simple to fit and straightforwardly provides confidence intervals for its fitted values. It allows a DT -like value to be derived, even from data that exhibit obvious “tailing.” We also showed how existing models of non-log-linear microbial inactivation, such as the Weibull model, can fit into a statistical linear model framework that dramatically simplifies their solution. We applied the log-quadratic model to thermal inactivation data for the spore-forming bacterium Clostridium botulinum and evaluated its merits compared with those of popular previously described approaches. The log-quadratic model was used as the basis of a secondary model that can capture the dependence of microbial inactivation kinetics on temperature. This model, in turn, was linked to models of spore inactivation of Sapru et al. and Rodriguez et al. that posit different physiological states for spores within a population. We believe that the log-quadratic model provides a useful framework in which to test vitalistic and mechanistic hypotheses of inactivation by thermal and other processes.

Inactivation Kinetics of Pathogens during Thermal Processing in Acidified Broth and Tomato Purée (pH 4.5)

2017 ◽  
Vol 80 (12) ◽  
pp. 2014-2021 ◽  
Author(s):  
Evann L. Dufort ◽  
Jonathan Sogin ◽  
Mark R. Etzel ◽  
Barbara H. Ingham
Keyword(s):  
Thermal Inactivation ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
E Coli ◽  
Log Reduction ◽  
Tomato Puree ◽  
Weibull Models ◽  
Canned Foods ◽  
D Values ◽  
Log Linear

ABSTRACT Thermal inactivation kinetics for single strains of Shiga toxin–producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella enterica were measured in acidified tryptic soy broth (TSB; pH 4.5) heated at 54°C. Inactivation curves also were measured for single-pathogen five-strain cocktails of E. coli O157:H7, L. monocytogenes, and S. enterica heated in tomato purée (pH 4.5) at 52, 54, 56, and 58°C. Inactivation curves were fit using log-linear and nonlinear (Weibull) models. The Weibull model yields the time for a 5-log reduction (t*) and a curve shape parameter (β). Decimal reduction times (D-values) and thermal resistance constants (z-values) from the two models were compared by defining t* = 5D* for the Weibull model. When the log-linear and Weibull models match at the 5-log reduction time, then t* = 5D* = 5D and D = D*. In 18 of 20 strains heated in acidified TSB, D and D* for the two models were not significantly different, although nonlinearity was observed in 35 of 60 trials. Similarly, in 51 of 52 trials for pathogen cocktails heated in tomato purée, D and D* were not significantly different, although nonlinearity was observed in 31% of trials. At a given temperature, D-values for S. enterica << L. monocytogenes < E. coli O157:H7 in tomato purée (pH 4.5). When using the two models, z-values calculated from the D-values were not significantly different for a given pathogen. Across all pathogens, z-values for E. coli O157:H7 and S. enterica were not different but were significantly lower than the z-values for L. monocytogenes. These results are useful for supporting process filings for tomato-based acidified food products with pH 4.5 and below and are relevant to small processors of tomato-based acidified canned foods who do not have the resources to conduct research on and validate pathogen lethality.

scholarly journals Evaluation of the Thermal Inactivation of a Salmonella Serotype Oranienburg Strain During Cocoa Roasting at Conditions Relevant to the Fine Chocolate Industry

2021 ◽  
Vol 12 ◽  
Author(s):  
Runan Yan ◽  
Gabriella Pinto ◽  
Rebecca Taylor-Roseman ◽  
Karen Cogan ◽  
Greg D’Alesandre ◽  
...  
Keyword(s):  
Foodborne Pathogens ◽  
Thermal Inactivation ◽  
Linear Models ◽  
Control Point ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
Critical Control Point ◽  
Chocolate Industry ◽  
Weibull Models ◽  
Log Linear

Cocoa roasting produces and enhances distinct flavor of chocolate and acts as a critical control point for inactivation of foodborne pathogens in chocolate production. In this study, the inactivation kinetics of Salmonella enterica subsp. enterica serotype Oranienburg strain was assessed on whole cocoa beans using roasting protocols relevant to the fine chocolate industry. Beans were inoculated with 107–108 log10 CFU/bean of Salmonella Oranienburg and roasted at 100–150°C for 2–100 min. A greater than 5 log10 reduction of S. Oranienburg was experimentally achieved after 10-min roasting at 150°C. Data were fitted using log-linear and Weibull models. The log-linear models indicated that the roasting times (D) needed to achieve a decimal reduction of Salmonella at 100, 110, 115, 120, 130, and 140°C were 33.34, 18.57, 12.92, 10.50, 4.20, and 1.90 min, respectively. A Weibull model indicated a decrease in the Salmonella inactivation rate over time (β < 1). Statistical analysis indicated that the Weibull model fitted the data better compared to a log-linear model. These data demonstrate the efficacy of cocoa roasting in inactivation of Salmonella and may be used to guide food safety decision-making.

Thermal Inactivation Kinetics of Three Heat-Resistant Salmonella Strains in Whole Liquid Egg

2019 ◽  
Vol 82 (9) ◽  
pp. 1465-1471 ◽  
Author(s):  
JOSHUA B. GURTLER ◽  
VIJAY K. JUNEJA ◽  
DEANA R. JONES ◽  
ANUJ PUROHIT
Keyword(s):  
Survival Data ◽  
Thermal Inactivation ◽  
Inactivation Kinetics ◽  
Glass Capillary ◽  
Circulating Water ◽  
Log Reduction ◽  
Heat Resistant ◽  
Weibull Models ◽  
D Values ◽  
Log Linear

ABSTRACT The heat resistance of three heat-resistant strains of Salmonella was determined in whole liquid egg (WLE). Inoculated samples in glass capillary tubes were completely immersed in a circulating water bath and held at 56, 58, 60, 62, and 64°C for predetermined lengths of time. The recovery medium was tryptic soy agar with 0.1% sodium pyruvate and 50 ppm of nalidixic acid. Survival data were fitted using log-linear, log-linear with shoulder, and Weibull models using GInaFiT version 1.7. Based on the R2 and mean square error, the log-linear with shoulder and Weibull models consistently produced a better fit to Salmonella survival curves obtained at these temperatures. Contaminated WLE must be heated at 56, 60, and 64°C for at least 33.2, 2.7, and 0.31 min, respectively, to achieve a 4-log reduction of Salmonella; 39.0, 3.1, and 0.34 min, respectively, for a 5-log reduction; and 45.0, 3.5, and 0.39 min, respectively, for a 6-log reduction. The z-values calculated from the D-values were 3.67 and 4.18°C for the log-linear with shoulder and Weibull models, respectively. Thermal death times presented in this study will be beneficial for WLE distributors and regulatory agencies when designing pasteurization processes to effectively eliminate Salmonella in WLE, thereby ensuring the microbiological safety of the product.

Influence of Heat Transfer with Tube Methods on Measured Thermal Inactivation Parameters for Escherichia coli

2007 ◽  
Vol 70 (4) ◽  
pp. 851-859 ◽  
Author(s):  
HYUN-JUNG CHUNG ◽  
SHAOJIN WANG ◽  
JUMING TANG
Keyword(s):  
Heat Transfer ◽  
Escherichia Coli ◽  
Heat Resistance ◽  
Bacterial Strain ◽  
Thermal Inactivation ◽  
Microbial Inactivation ◽  
Outer Diameter ◽  
Survival Curves ◽  
Log Linear ◽  
K 12

The purpose of this study was to investigate the influence of heat transfer on measured thermal inactivation kinetic parameters of bacteria in solid foods when using tube methods. The bacterial strain selected for this study, Escherichia coli K-12, had demonstrated typical first-order inactivation characteristics under isothermal test conditions. Three tubes of different sizes (3, 13, and 20 mm outer diameter) were used in the heat treatments at 57, 60, and 63°C with mashed potato as the test food. A computer model was developed to evaluate the effect of transit heat transfer behavior on microbial inactivation in the test tubes. The results confirmed that the survival curves of E. coli K-12 obtained in 3-mm capillary tubes were log linear at the three tested temperatures. The survival curves observed under nonisothermal conditions in larger tubes were no longer log linear. Slow heat transfer alone could only partially account for the large departures from log-linear behavior. Tests with the same bacterial strain after 5 min of preconditioning at a sublethal temperature of 45°C revealed significantly enhanced heat resistance. Confirmative tests revealed that the increased heat resistance of the test bacterium in the center of the large tubes during the warming-up periods resulted in significantly larger D-values than those obtained with capillary tube methods.

Enhanced Thermal Resistance of Salmonella in Marinated Whole Muscle Compared with Ground Pork

2010 ◽  
Vol 73 (2) ◽  
pp. 372-375 ◽  
Author(s):  
ADRIANA VELASQUEZ ◽  
TASHA J. BRESLIN ◽  
BRADLEY P. MARKS ◽  
ALICIA ORTA-RAMIREZ ◽  
NICOLE O. HALL ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Physical State ◽  
Thermal Inactivation ◽  
Heating Temperature ◽  
Inactivation Kinetics ◽  
Pork Products ◽  
Ground Pork ◽  
Lag Times ◽  
Log Linear ◽  
Whole Muscle

The internal muscle environment may enhance thermal resistance of bacterial pathogens. Based on the migration of pathogens into whole muscle products during marination, the validity of current thermal inactivation models for whole muscle versus ground products has been questioned. Consequently, the objective of this work was to compare thermal resistance of Salmonella in whole muscle versus ground pork. Irradiated samples of whole and ground pork loin (5.5 to 7.5 g) were exposed to a Salmonella-inoculated (108 CFU/ml) marinade (eight serovar cocktail) for 20 min, placed in sterile brass tubes (12.7 mm diameter), sealed, and heated isothermally at 55, 58, 60, 62, or 63°C, and surviving salmonellae were enumerated on Petrifilm aerobic count plates. The thermal lag times and initial bacterial counts were similar for both whole muscle and ground samples (P > 0.05), with all samples having equivalent compositions, inocula, and thermal histories. Heating temperature and physical state of the meat (whole versus ground muscle) affected Salmonella inactivation, with greater thermal resistance observed in whole than in ground muscle (P < 0.05). Assuming log-linear inactivation kinetics, Salmonella was 0.64 to 2.96 times more heat resistant in whole muscle than in ground pork. Therefore, thermal process validations for pork products should also account for the physical state of the product to ensure microbial safety.

Thermal Inactivation Kinetics of Salmonella and Enterococcus faecium NRRL-B2354 on whole chia seeds (Salvia hispanica L.)

2021 ◽  
Author(s):  
Soon Kiat Lau ◽  
Rajendra Panth ◽  
Byron D Chaves ◽  
Curtis L Weller ◽  
Jeyamkondan Subbiah
Keyword(s):  
Enterococcus Faecium ◽  
Thermal Inactivation ◽  
Fatty Acid Content ◽  
Information Criterion ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
Primary Model ◽  
Log Linear ◽  
Kinetics Of ◽  
Thermal Pasteurization

Intervention technologies for inactivating Salmonella in whole chia seeds are currently limited. The determination of the thermal inactivation kinetics of Salmonella o n chia seeds and selection of an appropriate nonpathogenic surrogate will provide a knowledge foundation for selecting and optimizing thermal pasteurization processes for chia seeds. In this study, chia seed samples from three separate production lots were inoculated with a five strain Salmonella cocktail or Enterococcus faecium NRRL-B2354 and equilibrated to 0.53 aw at room temperature (25 °C). After equilibration for at least three days, the inoculated seeds were subjected to isothermal treatments at 80, 85, or 90 °C. Samples were taken out at six timepoints and enumerated for survivors. Initial dilution of whole chia seeds was performed in a filter bag at a 1:30 ratio after it was shown to have similar recovery to grinding the seeds. Survivor data were fitted to consolidated models consisting of a primary model (log-linear or Weibull) and one secondary model (Bigelow). E. faecium exhibited higher thermal resistance than Salmonella , suggesting its suitability as a conservative nonpathogenic surrogate. The Weibull model was a better fit for the survivor data than the log-linear model for both bacteria due to its lower root mean square error and corrected Akaike’s Information Criterion values. Measurements of lipid oxidation and fatty acid content indicated a few statistically different values compared to the control samples, but the overall difference in magnitudes were relatively small. The thermal inactivation kinetics of Salmonella and E. faecium o n chia seeds as presented in this study can serve as a basis for developing thermal pasteurization processes for chia seeds.

Ultraviolet inactivation of bacteria and model viruses in coconut water using a collimated beam system

2019 ◽  
Vol 25 (7) ◽  
pp. 562-572 ◽  
Author(s):  
Manreet S Bhullar ◽  
Ankit Patras ◽  
Agnes Kilonzo-Nthenge ◽  
Bharat Pokharel ◽  
Michael Sasges
Keyword(s):  
Pathogenic Bacteria ◽  
Microbial Inactivation ◽  
Coconut Water ◽  
Inactivation Kinetics ◽  
E Coli ◽  
Log Reduction ◽  
Ultraviolet C ◽  
Log Linear ◽  
Kinetics Of ◽  
Collimated Beam

This study investigated the effect of ultraviolet-C irradiation on the inactivation of microorganisms in coconut water, a highly opaque liquid food (1.01 ± 0.018 absorption coefficient). Ultraviolet-C inactivation kinetics of two bacteriophages (MS2, T1UV) and three surrogate bacteria ( Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes) in 0.1% (w/v) peptone and coconut water were investigated. Ultraviolet-C irradiation at 254 nm was applied to stirred samples, using a collimated beam device. A series of known ultraviolet-C doses (0–40 mJ cm−2) were applied for ultraviolet-C treatment except for MS2 where higher doses were delivered (100 mJ cm−2). Inactivation levels of all organisms were proportional to ultraviolet-C dose. At the highest dose of 40 mJ cm−2, three surrogates of pathogenic bacteria were inactivated by more than 5-log10 (p < 0.05) in 0.1% (w/v) peptone and coconut water. Results showed that ultraviolet-C irradiation effectively inactivated bacteriophage and surrogate bacteria in highly opaque coconut water. The log reduction kinetics of microorganisms followed log-linear and exponential models with higher R2 (>0.95) and low root mean square error values. The D10 values of 3, 5.48, and 4.58 mJ cm−2 were obtained from the inactivation of E. coli, S. Typhimurium, and L. monocytogenes, respectively. Models for predicting log reduction as a function of ultraviolet-C irradiation dose were found to be significant (p < 0.05). Fluid optics were the key controlling parameters for efficient microbial inactivation. Therefore, the ultraviolet-C dose must be calculated not only from the incident ultraviolet-C intensity but must also consider the attenuation in the samples. The results from this study imply that adequate log reduction of vegetative cells and model viruses is achievable in coconut water and suggested significant potential for ultraviolet-C treatment of other liquid foods.

Effect of moderate thermal treatments on the inactivation of a strain of Listeria monocytogenes and physicochemical properties of soursop pulp

2020 ◽  
Vol 26 (6) ◽  
pp. 535-548
Author(s):  
Almadalia Velasco-Hernández ◽  
Crescenciano Saucedo-Veloz ◽  
Martha Elva Ramírez-Guzmán ◽  
Sergio Humberto Chávez-Franco ◽  
Salvador Valle-Guadarrama ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Goodness Of Fit ◽  
Thermal Inactivation ◽  
Inactivation Kinetics ◽  
Thermal Treatments ◽  
Tropical Fruit ◽  
Gompertz Equation ◽  
Commercially Important ◽  
Pulp Processing ◽  
Log Linear

Soursop ( Annona muricata L.) is a commercially important tropical fruit, whether fresh or processed as a pasteurized or frozen pulp used to prepare juice, drinks, nectar, ice cream, popsicles, and desserts. Besides preserving quality, another preoccupation in the processing of fruit pulps is product safety. Several studies show the association between pulp processing and the development of various microorganisms; however, few have focused on the association between L. monocytogenes and the pulp of sour fruits. The objective was to evaluate the effect of moderate thermal treatments on the inactivation of L. monocytogenes and the physicochemical properties in soursop pulp in order to determine the best processing conditions that will allow to maintain quality as well as to achieve an adequate level of safety. Thermal inactivation kinetics were obtained for L. monocytogenes inoculated in soursop pulp at five levels of temperature (50, 52.5, 55, 57.5, and 60 ℃) and different exposure times (0–60 min). The survival curves did not suggest a log-linear relationship, and were, consequently, fitted to the modified Gompertz equation. The results indicated that the modified Gompertz equation provided an acceptable goodness of fit. Five-log10 cycles reductions of L. monocytogenes were achieved at 50 ℃/60 min, 52.5 ℃/16 min, 55 ℃/10 min, 57.5 ℃/5 min, and 60 ℃/1.25 min. These 5-log10 treatments applied to the soursop pulp indicated that the soursop pulp showed changes in the color parameters and a decrease in the content of total sugars, reducing sugars, ascorbic acid, total phenols, and pH.

An Integral Model of Microbial Inactivation Taking into Account Memory Effects: Power-Law Memory Kernel

2009 ◽  
Vol 72 (4) ◽  
pp. 837-842 ◽  
Author(s):  
NIRUPAMA VAIDYA ◽  
CARLOS M. CORVALAN
Keyword(s):  
Power Law ◽  
Thermal Stresses ◽  
Thermal Inactivation ◽  
Cell Damage ◽  
Microbial Inactivation ◽  
Memory Effects ◽  
Memory Model ◽  
Integral Model ◽  
Microbial Response ◽  
Log Linear

In this article, we propose an alternative framework for the description of non–log-linear thermal inactivation of microorganisms. The proposed framework generalizes classical views by explicitly taking into account memory effects, such as those often associated with cumulative cell damage or progressive cell adaptation. Within this general framework, specialized memory models can be easily accommodated to describe different modes of microbial response to previous thermal stresses. In this introductory study, the advantages and limitations of the simplest nontrivial memory model, the power-law memory model, were explored. Our results indicate that for isothermal treatments the assumption of power-law memory leads to a simple solution that is known to describe a large number of non–log-linear survival curves. For nonisothermal treatments, the power-law memory model leads to predictions that agree well with experimental data. This research may lead to new insights into predictive microbiology with a new appreciation for the importance of memory effects.

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