A new high temperature short time process for microbial decontamination of seeds and food powders

The process for heat treatment of seeds and food powders patented and developed by our laboratory is based on very short heat stresses (from 0.1 up to 30 s) at very high temperatures (in the range of 200 to 600 °C) followed by an instantaneous cooling due to a cold gas (− 80 °C). The decontamination of dried powders is difficult, and the difficulty correlates with the presence of a specific microflora adapted to low water content. Using this new thermal process, experiments with Bacillus subtilis spores and Saccharomyces cerevisiae cells dried on glass beads were carried out. Destruction levels obtained are in the range of 5 to 8 log according to initial water activity level. Our results showed that heat resistance of spores and vegetative cells was strongly improved for initial aw values in the range of 0.3 to 0.5. Our work also evaluated the effects of microbial distribution and powder granulometry on decontamination efficiency. The impact of heat treatment on product organoleptic qualities, notably color, has been also measured.