Date of this Version
Development of pre-milling intervention strategies to improve the microbial quality of wheat and wheat-based products is an emerging concern for the food industry. When steam tempering conditions for hard and soft wheat were applied, the microbial population associated with the grain was significantly reduced compared to controls. Further reductions were observed when acid was applied as part of the intervention which is an added benefit since the addition of a tempering solution is required for both wheat classes since the desired milling moisture cannot be reached by applying steam alone. On average, the highest reductions for hard wheat were achieved for Aerobic Plate Count (APC), molds and Enterobacteriaceae showing an average reduction of up to 4.78, 4.26 and 3.64 log CFU/g, respectively. While for soft wheat the highest microbial reduction was achieved for Enterobacteriaceae (up to 4.34 log CFU/g), followed by APC (up to 4.0 log CFU/g). For both wheat classes studied, the increased bed depth and temperature increased the microbial reduction. While the inoculation studies showed that saturated steam was most effective against the non-pathogenic E. coli population, with the highest reduction of 3.43 log CFU/g. On the other hand, E. faecium reductions showed a different trend. Acid with steam achieved the highest reduction for all bed depths and temperatures. When the temperature was decreased to 80°C the efficacy of the steam decreased as well. Furthermore, the functional properties of the flour were evaluated and a few significant differences between the control and treated samples. However, the treatments did not substantially affect the functional properties of soft and hard wheat straight-grade flour when cookies and bread were made from them, respectively. Therefore, the use of steam, or a combination of steam and acid, may be an alternative intervention applied by the milling industry to reduce microbial population in hard and soft wheat.
Advisor: Andréia Bianchini-Huebner