Characteristics of the inactivation of Escherichia coli by infrared irradiative heating

摘要

The inactivation of Escherichia coil by infrared (IR) irradiation was quantitatively evaluated and compared to that by thermal conductive heating. After the bulk temperature of the sterile saline irradiated by IR reached a steady given temperature, the E. coil culture was inoculated and IR heating was conducted. A mullite cylinder FIR heater, of which main wavelength is 4-7 microm, was used for IR heating. The killing of the E. coil by IR heating and thermal conductive heating both followed first-order reaction kinetics, and the apparent death rate constants (k) under different conditions were obtained. At the same temperatures, pasteurization by IR heating was more effective than that by thermal conductive heating, and its effectiveness increased with a decrease in liquid layer thickness. The values of k due to IR heating were approximately 2-3 times and one order larger than those due to thermal conductive heating at the liquid layer thickness of 10 mm and 1.5 mm, respectively. The activation energy (Ea) for the killing of E. coli by IR irradiation was slightly lower than that by thermal conductive heating, indicating that there are some differences in the action mechanisms.