The Weibull Model for Microbial Inactivation

2021 ◽  
Author(s):  
Sencer Buzrul
Keyword(s):  
Weibull Model ◽  
Microbial Inactivation

scholarly journals Application of a 360-Degree Radiation Thermosonication Technology for the Inactivation of Staphylococcus aureus in Milk

2021 ◽  
Vol 12 ◽  
Author(s):  
Jianwei Zhou ◽  
Lele Sheng ◽  
Ruiling Lv ◽  
Donghong Liu ◽  
Tian Ding ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Linear Models ◽  
Treatment Time ◽  
Limit Of Detection ◽  
Average Particle Size ◽  
Raw Milk ◽  
Weibull Model ◽  
Microbial Inactivation ◽  
Inactivation Kinetics ◽  
Average Particle

Milk is easy to be contaminated by microorganisms due to its abundant nutrients. In this study, a 360-degree radiation thermosonication (TS) system was developed and utilized for the inactivation of Staphylococcus aureus in milk. The 360-degree radiation TS system-induced inactivation kinetics of S. aureus was fitted best by the Weibull model compared with biphasic and linear models. The treatment time, the exposure temperature, and the applied ultrasound power was found to affect the bactericidal efficacy of the 360-degree radiation TS system. Additionally, the TS condition of 200 W and 63°C for 7.5 min was successfully applied to achieve complete microbial inactivation (under the limit of detection value) in raw milk. The treatment of 360-degree radiation TS can enhance the zeta potential and decrease the average particle size of milk. It also exhibited better retainment of the proteins in milk compared with the ultrahigh temperature and conventional pasteurization processing. Therefore, the 360-degree radiation TS system developed in this study can be used as an alternative technology to assure the microbiological safety and retain the quality of milk, and the Weibull model could be applied for the prediction of the inactivation levels after exposure to this technology.

scholarly journals Effect of Challenge Temperature and Solute Type on Heat Tolerance of Salmonella Serovars at Low Water Activity

2001 ◽  
Vol 67 (9) ◽  
pp. 4128-4136 ◽  
Author(s):  
K. L. Mattick ◽  
F. Jørgensen ◽  
P. Wang ◽  
J. Pound ◽  
M. H. Vandeven ◽  
...  
Keyword(s):  
Water Activity ◽  
Heat Tolerance ◽  
Weibull Model ◽  
Microbial Inactivation ◽  
Published Data ◽  
Death Rates ◽  
Factors Affecting ◽  
Serovar Typhimurium ◽  
Death Kinetics ◽  
Fail Safe

ABSTRACT Salmonella spp. are reported to have an increased heat tolerance at low water activity (aw; measured by relative vapor pressure [rvp]), achieved either by drying or by incorporating solutes. Much of the published data, however, cover only a narrow treatment range and have been analyzed by assuming first-order death kinetics. In this study, the death ofSalmonella enterica serovar Typhimurium DT104 when exposed to 54 combinations of temperature (55 to 80°C) and aw (rvp 0.65 to 0.90, reduced using glucose-fructose) was investigated. The Weibull model (LogS = −btn ) was used to describe microbial inactivation, and surface response models were developed to predict death rates for serovar Typhimurium at all points within the design surface. The models were evaluated with data generated by using six different Salmonella strains in place of serovar Typhimurium DT104 strain 30, two different solutes in place of glucose-fructose to reduce aw, or six low-awfoods artificially contaminated with Salmonella in place of the sugar broths. The data demonstrate that, at temperatures of ≥70°C, Salmonella cells at low aw were more heat tolerant than those at a higher aw but below 65°C the reverse was true. The same patterns were generated when sucrose (rvp 0.80 compared with 0.90) or NaCl (0.75 compared with 0.90) was used to reduce aw, but the extent of the protection afforded varied with solute type. The predictions of thermal death rates in the low-aw foods were usually fail-safe, but the few exceptions highlight the importance of validating models with specific foods that may have additional factors affecting survival.

Escherichia coli Thermal Inactivation Relative to Physiological State

2009 ◽  
Vol 72 (2) ◽  
pp. 399-402 ◽  
Author(s):  
D. GLENN BLACK ◽  
FEDERICO HARTE ◽  
P. MICHAEL DAVIDSON
Keyword(s):  
Escherichia Coli ◽  
Goodness Of Fit ◽  
Thermal Inactivation ◽  
Physiological State ◽  
Weibull Model ◽  
Growth Conditions ◽  
Coli Strain ◽  
Microbial Inactivation ◽  
Microbial Cells ◽  
K 12

Studies have explored the use of various nonlinear regression techniques to better describe shoulder and/or tailing effects in survivor curves. Researchers have compiled and developed a number of diverse models for describing microbial inactivation and presented goodness of fit analysis to compare them. However, varying physiological states of microorganisms could affect the measured response in a particular population and add uncertainty to results from predictive models. The objective of this study was to determine if the shape and magnitude of the survivor curve are possibly the result of the physiological state, relative to growth conditions, of microbial cells at the time of heat exposure. Inactivation tests were performed using Escherichia coli strain K-12 in triplicate for three growth conditions: statically grown cells, chemostat-grown cells, and chemostat-grown cells with buffered (pH 6.5) feed media. Chemostat cells were significantly less heat resistant than the static or buffered chemostat cells at 58°C. Regression analysis was performed using the GInaFiT freeware tool for Microsoft Excel. A nonlinear Weibull model, capable of fitting tailing effects, was effective for describing both the static and buffered chemostat cells. The log-linear response best described inactivation of the nonbuffered chemostat cells. Results showed differences in the inactivation response of microbial cells depending on their physiological state. The use of any model should take into consideration the proper use of regression tools for accuracy and include a comprehensive understanding of the growth and inactivation conditions used to generate thermal inactivation data.

Effects of Ohmic Heating, Including Electric Field Intensity and Frequency, on Thermal Inactivation of Bacillus subtilis Spores

2016 ◽  
Vol 80 (1) ◽  
pp. 164-168 ◽  
Author(s):  
SUGURU MURASHITA ◽  
SHUSO KAWAMURA ◽  
SHIGENOBU KOSEKI
Keyword(s):  
Bacillus Subtilis ◽  
Electric Field ◽  
Field Intensity ◽  
Survival Data ◽  
Electric Field Intensity ◽  
Thermal Inactivation ◽  
Ohmic Heating ◽  
Weibull Model ◽  
Microbial Inactivation ◽  
Inactivation Effect

ABSTRACT Methods for microbial inactivation are important in the food industry; however, conventional external heating (CH) reduces food quality. Accordingly, the nonthermal effects of ohmic heating (OH) on Bacillus subtilis spores in a sodium chloride aqueous solution at 101°C (i.e., the boiling point), as well as the effects of electric field intensity and frequency during OH, were investigated. Survival kinetics were compared between OH and external CH. The inactivation effect on B. subtilis was greater for all electric field conditions (5, 10, and 20 V/cm) than for CH. In particular, 20 V/cm showed a significantly higher inactivation effect (P < 0.05) on B. subtilis than those of CH at 8, 10, 12, 14, and 16 min. The survival data were fitted to various primary kinetic models. In the Weibull model and the log-linear model, there were significant differences (P < 0.05) in the rate parameters δ and kmax between OH at 20 V/cm and CH. However, there were no significant differences (P > 0.05) in survival kinetics between 20, 40, and 60 kHz; B. subtilis spores were inactivated more efficiently as the frequency increased. B. subtilis spores were almost completely inactivated at 14 to 16 min for the 60-kHz treatment, but spores were still alive at 20 and 40 kHz for the same treatment times. These results demonstrated that OH inactivates B. subtilis spores more effectively than CH. OH conditions with high electric field intensities and high frequencies resulted in efficient B. subtilis spore inactivation.

scholarly journals Use of Pulsed Electric Field for the Inactivation of Eupenicillium Javanicum Ascospores in Pineapple Juice

2021 ◽  
Vol 2049 (1) ◽  
pp. 012020
Author(s):  
Evelyn ◽  
Chairul ◽  
Komalasari ◽  
E Pebrianti ◽  
W Vazirani
Keyword(s):  
Electric Field ◽  
Uv Light ◽  
Pulsed Electric Field ◽  
Weibull Model ◽  
Pulse Number ◽  
Solid Content ◽  
Microbial Inactivation ◽  
Soluble Solid Content ◽  
Pineapple Juice ◽  
Log Reduction

Abstract Heat resistant molds are principle spoilage agents in foods and beverages with low acidity. The main objective of this work was to investigate the effect of 65 kV/cm PEF on the log reductions of Eupenicillium javanicum ascospores in 10–30°Brix pineapple juice as well as the modelling. Then, the first-order and Weibull parameters of the 65 kV/cm PEF inactivation of E. javanicum ascospores was estimated and compared. Further, the effect of PEF in combination with ultraviolet (UV) light treatment on the log reductions of E. javanicum ascospores was studied. Decreasing the soluble solid content of the juice from 30 to 10°Brix for 11.3 pulses increased the spore inactivation in pineapple juice by 2.7 log. A pulse number of 16 would be required by the 65 kV/cm PEF to achieve a 5-log reduction in juice. The Weibull model described spore inactivation by pulsed electric field. The estimated b-values for the 65 kV/cm PEF were 0.673 at 10°Brix, 0.041 at 20°Brix and 0.010 at 30°Brix, with n-values between 0.73 and 2.08. Although the combination of the PEF and UV light resulted in a slightly greater microbial inactivation, however two hurdles were not suggested. The results of this study confirmed the advantage of PEF technology for the inactivation of E. javanicum ascospores in pineapple juice.

Enhanced microbial inactivation by carbon dioxide through mechanical effects

2021 ◽  
pp. 105273
Author(s):  
Ratka Hoferick ◽  
Angelos Ntovas ◽  
Qasim Alhusaini ◽  
Mareike Müller ◽  
Stéphan Barbe ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Microbial Inactivation ◽  
Mechanical Effects

scholarly journals Ohmic Heating in the Food Industry: Developments in Concepts and Applications during 2013–2020

2021 ◽  
Vol 11 (6) ◽  
pp. 2507
Author(s):  
Zina T. Alkanan ◽  
Ammar B. Altemimi ◽  
Asaad R. S. Al-Hilphy ◽  
Dennis G. Watson ◽  
Anubhav Pratap-Singh
Keyword(s):  
Energy Consumption ◽  
Ohmic Heating ◽  
Bioactive Compound ◽  
Heating Time ◽  
Microbial Inactivation ◽  
Conventional Heating ◽  
Food Ingredients ◽  
Physico Chemical ◽  
Key Characteristics ◽  
Comparable Performance

Various technologies have been evaluated as alternatives to conventional heating for pasteurization and sterilization of foods. Ohmic heating of food products, achieved by passage of an alternating current through food, has emerged as a potential technology with comparable performance and several advantages. Ohmic heating works faster and consumes less energy compared to conventional heating. Key characteristics of ohmic heating are homogeneity of heating, shorter heating time, low energy consumption, and improved product quality and food safety. Energy consumption of ohmic heating was measured as 4.6–5.3 times lower than traditional heating. Many food processes, including pasteurization, roasting, boiling, cooking, drying, sterilization, peeling, microbiological inhibition, and recovery of polyphenol and antioxidants have employed ohmic heating. Herein, we review the theoretical basis for ohmic treatment of food and the interaction of ohmic technology with food ingredients. Recent work in the last seven years on the effect of ohmic heating on food sensory properties, bioactive compound levels, microbial inactivation, and physico-chemical changes are summarized as a convenient reference for researchers and food scientists and engineers.

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