Decontamination of Particulate Foods Using Intense Pulsed Light and Other Non-Thermal Technologies

Abstract

Low-moisture particulate foods comprise a wide range of food products such as milk powder, protein powder, egg powder, whey powder, spice, flour, grain, and seeds. Various pathogens or toxins such as C. sakazakii, Salmonella spp., Bacillus cereus spores, and deoxynivalenol (DON) were infected in particulate food matrices. These contaminants are physiologically dormant and metabolically quiescent in low moisture particulate foods and are therefore resistant to conventional thermal process. Conventional heating processes used to eliminate foodborne pathogens may cause some degrees of undesirable flavor and quality changes on particulate food products that are unacceptable for uses by consumers and food industries. This dissertation research focuses on developing non-thermal microbiocidal technologies for dry particulate foods. Lack of knowledge related to continuous nonthermal techniques on low-moisture particulate foods prevents the technology from applications in food industry. In this study, an intense pulsed light (IPL) treatment system was developed, processing parameters such as relative humidity, temperature, water activity, pulsed duration, voltage, pulsed frequency, and residence time, etc., were evaluated on different low-moisture particulate foods. After several generation-improvement of the IPL system and processes, the results showed a maximum of 4 log10 CFU/g reduction of microbe could be obtained after 60s IPL treatment on the conditions of 1 Hz and 3000 voltage. Furthermore, additional one log10 CFU/g microbial reduction could be achieved when combining IPL with TiO2 based catalysts. Food products such wheat, wheat kernels, and NFDM could be potentially subjected to IPL with minimized quality loss. For milk powder process, the IPL step can be fitted after spray drying. On the other hand, cold atmospheric plasma was able to inactivate be used to inactivate ~3 log10CFU/g of C. sakazakii in non-fat dry milk after only 120 s. However, the throughput of the system was limited and thereby, difficult to scale up. With respect to plasma activated water, the system was effective in degrading DON (34.6 %) in germinating barley samples while maintaining sample quality after 5 min. For microwave or catalytic microwave treatments, the results indicated microwave treatment below 60 °C was feasible to inactivate pathogens in wheat kernels up to 5 log10CFU/g at the water activity level of ~0.8. Therefore, the process can be fitted in a step after tempering. In summary, several nonthermal technologies specifically used for particulate food pasteurization were developed in the current research, optimized conditions for disinfection and particulate sample preservation were comprehensively investigated. The findings from this research has filled the key knowledge gaps of preventing the technology from commercialization.