Professor Iowa State University Ames, Iowa, United States
Abstract: Wheat bran, the coproduct of wheat flour processing, is a rich source of dietary fiber and is mostly utilized as a low-value product in animal feeds. In this research, the effects of two physical modifications of wheat bran (at 25 and 35% moisture) 1) grinding to < 500 mm, and 2) extrusion at two die temperature settings (high-140 and low-120°C) on fermentation, were evaluated with Lactobacillus plantarum and Bacillus subtillis. Extruded or ground brans were dispersed in water at 1:10 w/v, pH adjusted to 6.5 and pH 7, autoclaved at 121°C for 30 min, and inoculated (1% v/v) with L. plantarum and B. subtillis, respectively. The fermentation was carried out in 500 mL shake flasks at 37°C for 72 h with shaking at 200 rpm; 10 mL samples were taken out at 0, 6, 12, 24, 48, and 72 h time intervals for microbial viability and pH measurement. The highest growth rate of 0.43 h-1 and lower population doubling time of 1.62 h was observed for 140°C extruded wheat bran of 35% moisture fermented with Bacillus subtilis when compared to the control. The total carbohydrate content decreased from 10 mg/mL when fermented by both microbes. There was a significant reduction in total phenolic content from 15.9 to 6.68 mg GAE/ g when wheat brans of 35% moisture at 140°C were extruded compared to the ground non-extruded brans. Similarly, antinutritional compounds such as phytic acid and trypsin inhibitors were reduced by a maximum of 10% and 60% respectively, when extruded and fermented. In summary, all the extruded or ground wheat brans supported the growth of probiotic bacteria and positively affected the non-nutritive compounds, thereby improving the nutritional quality and usage making it favorable for food applications.
