Significance of wheat milling operations on the distribution of Escherichia coli bacterium into milling fractions

Background and Objectives Cross-contamination of pathogens is a common cause of food recalls. The objectives of this study were to quantify the amount of Escherichia coli transferred during wheat milling and to model the E. coli concentration in wheat flour fractions during milling. Findings Higher (p <= .05) E. coli counts were recovered in the nonflour mill fractions (1.9-4.5 log CFU/g) during the inoculated wheat milling run. The E. coli counts in flour fractions increased with more amounts (kg) of inoculated wheat milled. During the noninoculated mill run, E. coli counts decreased as more wheat was milled. Greater E. coli contamination was observed in the nonflour fractions (1.8-3.4 log CFU/g). The fitted models were significant (p <= .05) and had acceptable fit (R-2 = 0.40-0.85; SE = 0.16-0.42). Conclusion The findings indicate that E. coli contamination from wheat kernel could transfer into the flour at a lower concentration relative to nonflour fractions and that continuous milling of contaminated wheat increased flour E. coli counts. Significance and Novelty The results from this study may help development of mitigation strategies for pathogen contamination during milling and could be used for risk assessment analysis in wheat flour products.