Outbreaks linked to Salmonella and Shiga toxin-producing E. coli (STEC) in wheat flour led to increased interest in characterizing the fate of these pathogens on wheat grains during processing and exploring potential inactivation methods. Despite the increase in water activity of wheat grains to ~0.85, the changes in the pathogen populations on inoculated soft wheat grains remained relatively stable during tempering. Using confocal microscopy, no significant redistribution of pathogen was found based on the fluorescent intensity measurement. Chlorinated water had been used in the tempering solution in mills to control mold and yeast growth. When hard wheat grains were treated with 800ppm chlorinated water as a tempering over 18 hours, pathogen population changed from -2.35 to -0.30 log CFU/g, without negatively impacting the flour quality or functionality. Treating soft wheat at 75 ̊C using vacuum steam pasteurization, resulted in D75°C of Salmonella strains of 2.8 and 3.2 min of STEC ranges from 3.1 to 4.6 min, and of E. faecium was 3.3 min.
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