| Efficacy of pulsed UV-light and infrared heating for inactivation of pathogens was investigated. Pulsed UV-light was very effective in inactivating S. aureus on agar seeded cells and in phosphate buffer. Complete inactivation of S. aureus was achieved within 5-s treatments.;Raw milk inoculated with S. aureus was treated with pulsed UV-light by varying distance of milk sample from the quartz window, volume of milk, and treatment time. The log10 reduction obtained varied from 0.16 to 8.55 log10 CFU/ml. Complete inactivation of S. aureus was obtained at two conditions with corresponding reductions of 8.55 log10 CFU/ml.;Continuous treatment of milk was tested in order to determine the feasibility of industrial application of pulsed UV-light treatment. Reductions of S. aurues in milk varied from 0.55 to 7.26 log10 CFU/ml. Complete inactivation was achieved at two conditions. Sensory evaluation of pulsed UV-light treated pasteurized skim milk and 1% milk suggests that there was some perceivable change in the quality.;B. subtilis spores in water were treated with pulsed UV-light in an annular flow chamber. Flow rates up to 14 L/min resulted in complete inactivation of B. subtilis spores. No growth was observed during incubation under light and no-light conditions.;The efficacy of infrared heating on inactivation of S. aureus in milk was tested. The effect of depth of milk, infrared lamp temperature, and treatment time were investigated. Reductions of 0.10 to 8.41 log 10 CFU/ml were obtained for treatments up to 4 min.;The inactivation mechanism for pulsed UV-light and infrared heating was investigated using transmission electron microscopy (TEM) and spectroscopy. After 5-s treatment with pulsed UV-light, cell wall breakage, cytoplasm leakage, damage in the cellular membrane structure, and leakage of the cell content were observed by TEM. Infrared heat treated cells exhibited condensation of cytoplasm, cytoplasmic membrane damage, cell wall damage, and cellular content leakage occurred. The FTIR spectrometry was successfully used to classify the pulsed UV-light and infrared treated cells. |
