Effects of tempering with steam on the water distribution of wheat grains and quality properties of wheat flour.

• This paper presents a new technology for low bacterial wheat flour production. • Tempering with steam greatly shortened the tempering time of wheat grains. • Tempering with steam reduced the microbial load in tempered grains and wheat flour. • Tempering with steam changed grinding properties of wheat grains. • Tempering with steam improved the rheological properties of wheat flour. In this study, the effects of tempering with steam on the water distribution of wheat grains and the microbial load in wheat flour were investigated, as well as the physicochemical properties of wheat flour. Results showed that when steam treatment time was 320 s, the total plate count (TPC), yeast and mold count (YMC), and mesophilic aerobic spores (MAS) in flour decreased by 1.74, 1.99 and 1.01 lgCFU/g, respectively. Nuclear magnetic resonance (NMR) results showed that tempering with steam accelerated the water distribution of grains and significantly (p < 0.05) shortened the tempering time. Moreover, flour yield, particle size, ash content, and damaged starch content of flour were all altered. Furthermore, after tempering with steam, proteins were aggregated and starches were partially gelatinized, which caused dough development time and stability of flour increasing. Collectively, our findings indicated steam tempering could shorten the tempering time and improve the qualities of flour partly. [ABSTRACT FROM AUTHOR]