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Thermal Inactivation Kinetics (thermal + inactivation_kinetics)
Selected AbstractsTHERMAL INACTIVATION KINETICS OF ALKALINE PHOSPHATASE IN BUFFER AND MILKJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2006S. FADILO ABSTRACT A detailed kinetic study on the thermal inactivation of alkaline phosphatase (ALP) added into buffer and pasteurized milk and for ALP naturally present in raw cow's milk has been performed. Kinetic parameters (rate constant, k; decimal reduction time, D; activation energy, Ea; and z value) were evaluated based on the first-order rate model at 50,80C. The temperature sensitivity of the kinetic parameters was evaluated considering the Arrhenius-type Ea model. All kinetic behaviors were well described by the first-order model (r2 > 0.91). The D values increased with increasing temperature. Higher temperatures resulted in higher rates of enzyme inactivation as indicated by lower D values and higher k values. There are significant differences (P < 0.01) among the D values for ALP in buffer and milk at treated temperatures. The rate of enzyme inactivation was much more rapid in buffer than in pasteurized milk. The evaluated Ea values for ALP added into the buffer and pasteurized milk, and for ALP naturally present in raw milk were 97.2, 149.9 and 207.8 kJ/mol, respectively. The inactivation kinetics of ALP during heat treatment was found to be dependent on the composition of the medium, and the time and temperature of the heat treatment. [source] Thermal Inactivation Kinetics of Peroxidase and Lipoxygenase from Broccoli, Green Asparagus and CarrotsJOURNAL OF FOOD SCIENCE, Issue 1 2002E.F. Morales-Blancas ABSTRACT: Thewermal inactivation curves for peroxidase (POD) and lipoxygenase (LOX) in broccoli (florets), green asparagus (tip and stem), and carrots (cortex and core) extracts were determined in the range of 70 to 95 °C for 0 to 600 s. The capillary tube method was used to obtain quasi-isothermal conditions. The kinetics of both enzymes showed a biphasic first-order model, while at 70 °C, LOX in asparagus showed a monophasic first-order behavior. LOX activity was not detected for carrots. Kinetic parameters, k and Ea, were determined for heat-labile and heatresistant isoenzyme fractions. Additionally, initial and residual activities for both enzymes within tissue sections showed a different distribution and heat stability. [source] Thermal Inactivation Kinetics of Salmonella and Listeria in Ground Chicken Breast Meat and Liquid MediumJOURNAL OF FOOD SCIENCE, Issue 4 2000R.Y. Murphy ABSTRACT: Thermal inactivation of Listeria innocua and 6 Salmonella serotypes in ground chicken breast meat was compared to that in peptone (0.1%) - agar (0.1%) solution. Inoculated samples were packed in a thin-wall metal tube and submerged in a water bath at temperatures ranging from 55.0 to 70.0 °C. For Salmonella and Listeria, the D values in ground chicken breast meat at 55 to 70 °C were higher (p < 0.0001) than those in peptone-agar solution; however, the z values were not significantly different. Complete first-order inactivation models, with Arrhenius temperature dependency, were developed for each inoculum and medium. [source] Inactivation of Food Spoilage Microorganisms by Hydrodynamic Cavitation to Achieve Pasteurization and Sterilization of Fluid FoodsJOURNAL OF FOOD SCIENCE, Issue 9 2007P.J. Milly ABSTRACT:, Hydrodynamic cavitation is the formation of gas bubbles in a fluid due to pressure fluctuations induced by mechanical means. Various high-acid (pH , 4.6) fluid foods were processed in a hydrodynamic cavitation reactor to determine if commercial sterility can be achieved at reduced processing temperatures. Sporicidal properties of the process were also tested on a low-acid (pH < 4.6) fluid food. Fluid foods were pumped under pressure into a hydrodynamic cavitation reactor and subjected to 2 rotor speeds and flow rates to achieve 2 designated exit temperatures. Thermal inactivation kinetics were used to determine heat-induced lethality for all organisms. Calcium-fortified apple juice processed at 3000 and 3600 rpm rotor speeds on the reactor went through a transient temperature change from 20 to 65.6 or 76.7 °C and the total process lethality exceeded 5-log reduction of Lactobacillus plantarum and Lactobacillus sakei cells, and Zygosaccharomyces bailii cells and ascospores. Tomato juice inoculated with Bacillus coagulans spores and processed at 3000 and 3600 rpm rotor speeds endured a transient temperature from 37.8 to 93.3 or 104.4 °C with viable CFU reductions of 0.88 and 3.10 log cycles, respectively. Skim milk inoculated with Clostridium sporogenes putrefactive anaerobe 3679 spores and processed at 3000 or 3600 rpm rotor speeds endured a transient temperature from 48.9 to 104.4 or 115.6 °C with CFU reductions of 0.69 and 2.84 log cycles, respectively. Utilizing hydrodynamic cavitation to obtain minimally processed pasteurized low-acid and commercially sterilized high-acid fluid foods is possible with appropriate process considerations for different products. [source] | ||||||||||