Abstract
The effect of far-infrared (FIR) irradiation pasteurization on fungi was quantitatively evaluated and compared with the effect of thermal conductive heating. After the bulk temperature of the sterile saline irradiated by FIR reached a steady given temperature, yeast cells (Candida albicans NBRC 1950 and Saccharomyces cerevisiae NBRC 1067) or fungal spores (Aspergillus niger NBRC 4781) were inoculated and FIR heating was conducted. A mullite cylinder FIR heater, with a main wavelength of 4 - 7 μm, was used for FIR heating. Death of fungi by FIR heating and by thermal conductive heating both followed first-order reaction kinetics, and the apparent death rate constants under different temperature conditions were obtained. For the same bulk temperatures, pasteurization by FIR heating was more effective than thermal conductive heating. The activation energy for the death of fungi by FIR irradiation was slightly lower than thermal conductive heating, indicating differences in the mechanism of action.
Highlights
Infrared (IR) radiation is absorbed by water and organic materials
We evaluated the disinfection and pasteurization of liquid media and investigated the pasteurization kinetics of fungi suspended in saline by FIR heating under isothermal conditions
Assuming that the pasteurization of C. albicans by FIR irradiation follows first-order reaction kinetics as given by Equation (1) [22], the apparent first-order death rate constant, k, of C. albicans by FIR heating can be determined
Summary
Infrared (IR) radiation is absorbed by water and organic materials. IR heating is used widely for the drying, dehydration, blanching, thawing and pasteurization [1]-[5], as well as for medical treatment [6] [7]. The IR radiation cannot penetrate deep and heats up only a few millimeters. (2015) Effects of Far-Infrared Irradiative Heating Pasteurization on Fungi. During IR heating operations such as drying, blanching, roasting frying and cooking of food products, the pasteurization has progressed at the same time
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