scholarly journals Modelling inactivation kinetics of waterborne pathogens in municipal wastewater using ozone

2019 ◽  
Vol 25 (6) ◽  
pp. 890-897
Author(s):  
Achisa C Mecha ◽  
Maurice S Onyango ◽  
Aoyi Ochieng ◽  
Maggy NB Momba
Keyword(s):  
Municipal Wastewater ◽  
Bacterial Species ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
Waterborne Diseases ◽  
Bacterial Inactivation ◽  
Survival Curves ◽  
Water Matrix ◽  
Weibull Models ◽  
Log Linear

Microbial water pollution is a key concern leading to waterborne diseases. This study evaluated the disinfection of wastewater using ozonation. The following aspects were investigated: inactivation efficiency against <i>Escherichia coli, Salmonella</i> species, <i>Shigella</i> species, and <i>Vibrio cholerae</i>; modelling of inactivation kinetics using disinfection models; and evaluation of microbial regrowth studies. 99% bacterial inactivation was obtained within 15 min, irrespective of the water matrix, showing the strong oxidizing potential of ozone. The disinfection data were fitted into the log-linear and Weibull models. The survival curves were non-linear and fitted the Weibull model (fractional bias and normalized mean square error equal to 0.0), especially at high bacterial concentrations (10<sup>6</sup> CFU/mL). The inactivation occurred in two stages: an initial rapid stage (15 min) and a final slow stage exhibiting a tailing mechanism (15-45 min) probably as a result of the self-defence mechanisms adopted by the bacteria to limit oxidative stress. Considering the pattern of survival curves, no significant differences (<i>p</i> > 0.05) were observed among the four tested bacterial species; thus showing that ozone was effective against all the bacteria tested. There was minimal bacterial regrowth in the treated samples 24 h after ozone disinfection with reactivation values of 0-5% obtained.

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 &lt;&lt; L. monocytogenes &lt; 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 &lt; 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.

scholarly journals Combined Effect of Temperature and Relative Humidity on the Survival of Salmonella Isolates on Stainless Steel Coupons

2022 ◽  
Vol 19 (2) ◽  
pp. 909
Author(s):  
Amreen Bashir ◽  
Peter A. Lambert ◽  
Yvonne Stedman ◽  
Anthony C. Hilton
Keyword(s):  
Stainless Steel ◽  
Relative Humidity ◽  
Storage Conditions ◽  
Effect Of Temperature ◽  
Inactivation Kinetics ◽  
Survival Curves ◽  
Weibull Models ◽  
Higher Temperature ◽  
Modified Weibull ◽  
Log Linear

The survival on stainless steel of ten Salmonella isolates from food factory, clinical and veterinary sources was investigated. Stainless steel coupons inoculated with Salmonella were dried and stored at a range of temperatures and relative humidity (RH) levels representing factory conditions. Viability was determined from 1 to 22 days. Survival curves obtained for most isolates and storage conditions displayed exponential inactivation described by a log-linear model. Survival was affected by environmental temperatures and RH with decimal reduction times (DRTs) ranging from <1 day to 18 days. At 25 °C/15% RH, all isolates survived at levels of 103 to 105 cfu for >22 days. Furthermore, temperatures and RH independently influenced survival on stainless steel; increasing temperatures between 10 °C and 37 °C and increasing RH levels from 30–70% both decreased the DRT values. Survival curves displaying a shoulder followed by exponential death were obtained for three isolates at 10 °C/70% RH. Inactivation kinetics for these were described by modified Weibull models, suggesting that cumulative injury occurs before cellular inactivation. This study highlights the need to control temperature and RH to limit microbial persistence in the food manufacturing environment, particularly during the factory shut-down period for cleaning when higher temperature/humidity levels could be introduced.

Modeling Penicillium expansum Resistance to Thermal and Chlorine Treatments

2009 ◽  
Vol 72 (12) ◽  
pp. 2618-2622 ◽  
Author(s):  
BEATRIZ C. M. SALOMÃO ◽  
JOHN J. CHUREY ◽  
GLÁUCIA M. F. ARAGÃO ◽  
RANDY W. WOROBO
Keyword(s):  
Apple Juice ◽  
Weibull Model ◽  
Superior Performance ◽  
Penicillium Expansum ◽  
Heat Inactivation ◽  
Survival Curves ◽  
Biphasic Model ◽  
Log Reduction ◽  
Weibull Models ◽  
D Values

Apples and apple products are excellent substrates for Penicillium expansum to produce patulin. In an attempt to avoid excessive levels of patulin, limiting or reducing P. expansum contamination levels on apples designated for storage in packinghouses and/or during apple juice processing is critical. The aim of this work was (i) to determine the thermal resistance of P. expansum spores in apple juice, comparing the abilities of the Bigelow and Weibull models to describe the survival curves and (ii) to determine the inactivation of P. expansum spores in aqueous chlorine solutions at varying concentrations of chlorine solutions, comparing the abilities of the biphasic and Weibull models to fit the survival curves. The results showed that the Bigelow and Weibull models were similar for describing the heat inactivation data, because the survival curves were almost linear. In this case, the concept of D- and z-values could be used, and the D-values obtained were 10.68, 6.64, 3.32, 1.14, and 0.61 min at 50, 52, 54, 56, and 60°C, respectively, while the z-value was determined to be 7.57°C. For the chlorine treatments, although the biphasic model gave a slightly superior performance, the Weibull model was selected, considering the parsimony principle, because it has fewer parameters than the biphasic model has. In conclusion, the typical pasteurization regimen used for refrigerated apple juice (71°C for 6 s) is capable of achieving a 6-log reduction of P. expansum spores.

Persistence of Non-O157 Shiga Toxin–Producing Escherichia coli in Dairy Compost during Storage

2017 ◽  
Vol 80 (12) ◽  
pp. 1999-2005 ◽  
Author(s):  
Hongye Wang ◽  
Muthu Dharmasena ◽  
Zhao Chen ◽  
Xiuping Jiang
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Survival Data ◽  
Weibull Model ◽  
Storage Conditions ◽  
Scientific Data ◽  
Pathogen Population ◽  
Weibull Models ◽  
Subsequent Storage ◽  
Log Linear

ABSTRACT Dairy compost with 20, 30, or 40% moisture content (MC) was inoculated with a mixture of six non-O157 Shiga toxin–producing Escherichia coli (STEC) serovars at a final concentration of 5.1 log CFU/g and then stored at 22 and 4°C for 125 days. Six storage conditions—4°C and 20% MC, 4°C and 30% MC, 4°C and 40% MC, 22°C and 20% MC, 22°C and 30% MC, and 22°C and 40% MC—were investigated for the persistence of non-O157 STEC in the dairy compost. During the entire storage, fluctuations in indigenous mesophilic bacterial levels were observed within the first 28 days of storage. After inoculation, the non-O157 STEC population increased 0.69 and 0.79 log CFU/g in the dairy compost with 30 and 40% MC at 22°C within the first day, respectively; for all other storage conditions, the pathogen population decreased rapidly. After the 125-day storage, the reductions of non-O157 STEC for 4°C and 20% MC, 4°C and 30% MC, 4°C and 40% MC, 22°C and 20% MC, 22°C and 30% MC, and 22°C and 40% MC storage conditions were &gt;4.52, &gt;4.55, 3.89, &gt;4.61, 3.60, and 3.17 log CFU/g, respectively. All the survival curves showed an extensive tail, indicating non-O157 STEC can survive at least for 125 days in the dairy compost. The survival data were analyzed with log-linear with tailing and Weibull models. Compared with the log-linear with tailing model, the Weibull model was found to be a better choice for predicting the survival of non-O157 STEC in dairy compost owing to a high overall R2 value (0.8738 to 0.9909). The decay rate of non-O157 STEC was higher in dairy compost stored at 4°C compared with at 22°C, and the same trend was found for the compost with 40% MC versus 20% MC. In addition, two non-O157 STEC serotypes (STEC O145 and O45) were detected on the last day of the longitudinal study and may deserve special attention in the Big 6 STEC group. Our results have provided scientific data for risk assessment of the microbiological safety of dairy compost to control non-O157 STEC during subsequent storage of dairy compost.

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.

scholarly journals Synthesis and application of g-C3N4/Fe3O4/Ag nanocomposite for the efficient photocatalytic inactivation of Escherichia coli and Bacillus subtilis bacteria in aqueous solutions

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Soudabeh Ghodsi ◽  
Ali Esrafili ◽  
Hamid Reza Sobhi ◽  
Roshanak Rezaei Kalantary ◽  
Mitra Gholami ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Uv Light ◽  
Weibull Model ◽  
Bacterial Density ◽  
Light Irradiation ◽  
Waterborne Diseases ◽  
Bacterial Inactivation ◽  
E Coli ◽  
Uv Light Irradiation ◽  
Ft Ir

AbstractContamination of water with bacteria is one of the main causes of waterborne diseases. The photocatalytic method on the basis of bacterial inactivation seems to be a suitable disinfectant due to the lack of by-products formation. Herein, g-C3N4/Fe3O4/Ag nanocomposite combined with UV-light irradiation was applied for the inactivation two well-known bacteria namely, E. coli and B. subtilis. The nanocomposite was prepared by a hydrothermal method, and subsequently it was characterized by XRD, FT-IR, SEM, EDX and PL analyses. The optimum conditions established for the inactivation of both bacteria were as follows: nanocomposite dosage 3 g/L and bacterial density of 103 CFU/mL. In the meantime, the efficient inactivation of E. coli and B. subtilis took 30 and 150 min, respectively. The results also revealed that inactivation rate dropped with an increase in the bacterial density. It is also pointed out that OH˚ was found out to be the main radical species involved in the inactivation process. Finally, the kinetic results indicated that the inactivation of E. coli and B. subtilis followed the Weibull model. It is concluded that C3N4/Fe3O4/Ag nanocomposite along with UV-light irradiation is highly effective in inactivating E. coli and B. subtilis bacteria in the aqueous solutions.

scholarly journals Modelling the inactivation of Staphylococcus aureusat moderate heating temperatures

2021 ◽  
Vol 39 (No. 1) ◽  
pp. 42-48
Author(s):  
Veronika Lehotová ◽  
Karla Miháliková ◽  
Alžbeta Medveďová ◽  
Ľubomír Valík
Keyword(s):  
Weibull Model ◽  
Primary Data ◽  
Coefficient Of Determination ◽  
Decimal Reduction Time ◽  
Capillary Method ◽  
Fitting Procedure ◽  
Bacterial Contaminants ◽  
Weibull Models ◽  
One Step ◽  
Log Linear

The survival of bacterial contaminants at moderate processing temperatures is of interest to many food producers, especially in terms of the safety and quality of the final products. That is why the heat resistance of Staphylococcus aureus 2064, an isolate from artisanal Slovakian cheese, was studied in the moderate temperature range (57–61 °C) by the capillary method. The fourth decimal reduction time t<sub>4D</sub>- and z-values were estimated in two steps by traditional log-linear Bigelow and non-linear Weibull models. In addition, a one-step fitting procedure using the Weibull model was also applied. All the approaches provided comparable t<sub>4D</sub>-values resulting in the following z-values of 11.8 °C, 12.3 °C and 11.3 °C, respectively. Moreover, the one-step approach takes all the primary data into z-value calculation at once, thus providing a more representative output at the reasonable high coefficient of determination R<sub>2</sub> = 0.961

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.

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.

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