Microbial Inactivation Kinetics Research Articles

Critical factors determining inactivation kinetics by pulsed electric field food processing

The potential to commercialize the non-thermal pulsed electric field (PEF) technology as a new method to preserve food products has caught the attention of the food industry that wishes to fulfil consumers demands for fresh products. In recent years, numerous research groups have demonstrated the possibility to inactivate a range of microorganisms both in buffer systems and in food products using different PEF systems. In this review, we survey the critical process factors and main characteristics of food products that determine the microbial inactivation kinetics.

Kinetic Analysis of Microbial Inactivation by Microwave Irradiation based on Temperature History.

The kinetics of microbial inactivation by microwave irradiation were studied from the viewpoint of thermal inactivation analysis. From the temperature history of a microbial suspension during irradiation, a thermal inactivation curve was predicted. The predicted curves were similar to experimentally produced curves by irradiation at various energy outputs, showing that the inactivation was predominantly due to the heat induced by irradiation. On the other hand, a small difference in the inactivation rate between the curves was observed at a high output. This implied the possible existence of nonthermal factors in irradiation lethality.

MODELING MICROWAVE COOKING of COCKTAIL SHRIMP

A mathematical model for microwave cooking of cocktail shrimp was developed. the model included heat and mass transfer and microbial inactivation kinetics. A simple 2 dimensional cylindrical slab geometry was used and model equations were solved using the finite difference method. the model predictions on temperature and mass loss were in good agreement with the observed data. Temperature predictions were within ± 6C and mass predictions were within ± 2 g of the observed data.

Statistics of Microbial Disinfection

Engineering adequate disinfection processes and assessing risks associated with various disinfection options requires knowledge of kinetics of microbial inactivation as a function of design variables (e.g., dose, contact time). Often such information is obtained in batch studies and extrapolated to design conditions. By Monte Carlo techniques, we have shown that the use of a direct maximum likelihood evaluation for two types of data normally encountered, counts (PFU or CFU) and dilution experiments (MPN), leads to estimates of microbial inactivation rate parameters having lower bias and variance than other data reduction normally employed. This paper reviews the methodology of this technique and provides the theory for the computation of confidence limits for parameter estimates, and discusses how the data may be checked for consistency (goodness of fit determination).

Kinetics of microbial inactivation by chlorine—I Review of results in demand-free systems

Comparaison de modeles cinetiques. Resumes statistiques des resultats pour du chlore libre ou combine. Parametres chick-Watson pour l'inactivation microbienne par le chlore libre ou combine

Kinetics of microbial inactivation by chlorine—II Kinetics in the presence of chlorine demand

Description et analyse des cinetiques de decomposition des coliformes dans l'eau usee a l'aide du modele empirique de Selleck

A model describing microbial inactivation and growth kinetics

A model based on the chance of collision between environmental water molecules having appropriate energy and microbial cells, and leading to description of both inactivation and growth kinetics is presented. Functions derived from the model can describe the known shapes of survival curves (concave, convex, sigmoid, linear, on semi-log plot), the tailing-off phenomenon, some prominent behaviour of growing population kinetics, and are provided with fair predictive power. The main features of the model as heat inactivation is concerned are: (1) always the survival curves are expected to be concave on semi-log plot, unless some lag occurs in reaching the treatment temperature; (2) the tailing-off occurs when the concentration of living cells and/or water molecules having lethal energy is low enough; (3) heat inactivation curve at any temperature and whichever is the water content of the medium can easily be predicted, provided a single survivor concentration after time t at temperature T in a medium of defined composition is known; (4) the energy value of molecules leading to inactivation is about half the activation energy expected from classical thermodynamic treatment of reaction rate; (5) the concentration of water molecules having enough energy to drive the process changes exactly Q 10 times each 10 °C or ten times each z degrees. As radiation or chemical inactivation is concerned the model allows the description of known shapes of survival curves, linking the shape of the survival curve to the concentration of specific cellular molecular groups. Appropriate modification of the fundamental equation of the model leads to description of cell growth kinetics as a function of cell concentration, temperature, water content in the environment, the presence of metabolic by-products, antimetabolites, etc., as well as to the formulation of hypotheses about growth, death and senescence regulating structures.

Sterilization of Foods

Thermal processing is the standard to design sterilization processes through the general and formula methods. Bigelow established the foundations for the current procedures of thermal food-processing design by defining the decimal reduction time ( D ) concept and its temperature dependence ( z T ). Additionally, Bigelow developed the general method to define the processing time by calculating the area under the curve when the lethality is plotted against time. Ball implemented the formula method to simplify the calculations of process lethality by generating charts and tables that correlate the temperature profile of the food product with microbial inactivation kinetics data.