EFFICACY OF INFRARED HEAT TREATMENT FOR INACTIVATION OF STAPHYLOCOCCUS AUREUS IN MILK

Abstract

ABSTRACT The efficacy of infrared (IR) heating for inactivation of Staphylococcus aureus, a pathogenic microorganism, in milk was studied to investigate the potential of this technology for milk processing. S. aureus population was reduced from 0.10 to 8.41 log10 cfu/mL, depending upon the treatment conditions. The effects of IR lamp temperatures (536 and 619C), volumes of treated milk samples (3, 5 and 7 mL) and treatment times (1, 2 and 4 min) on the lethality of targeted microbes were found to be statistically significant (P < 0.05). Complete inactivation of S. aureus was obtained in two cases within 4 min at a 619C lamp temperature, resulting in 8.41 log10 cfu/mL reduction. Enrichment resulted in growth as some of the injured cells were able to repair. Further investigation of IR heating for longer treatment times (>4 min) indicated that there was no growth observed following the enrichment in most cases for treatment at the lamp temperature of 619C. The results demonstrated that IR heating has a potential for effective inactivation of S. aureus in milk.To ensure the sterility efficacy, the heating patterns of milk samples under IR radiation were simulated using computational fluid dynamics codes in three dimensions with user‐defined functions for radiative internal energy source terms. The predicted temperature values were in good agreement with the experimental data with the maximum prediction error of 5.2C. Further optimization of the process parameters, i.e., temperature and heating time, using the developed model is expected to ensure that even underprocessed food components will receive desirable doses of lethality, which can result in a commercially successful milk pasteurization method.PRACTICAL APPLICATIONSInfrared (IR) heating has been used in the food industry as a heating or drying method because of several advantages such as minimal deterioration in food quality, faster heating and higher energy efficiency. IR heating can effectively inactivate pathogenic microorganisms in dairy products compared with conventional heating. IR heating cannot only effectively inactivate pathogenic microorganisms in dairy foods, but also preserve the quality. Furthermore, IR heating is found to be cost effective as it can reduce the energy consumption up to 44% for various food products compared with conventional heating. Results from this study could provide a basis for the application of IR heat treatment for dairy food processing. Further investigation on sensory and quality changes during IR heating can shed light on the efficacy of this process and may provide a potential novel pasteurization method for the dairy industry.