Professor Iowa State University Ames, Iowa, United States
Abstract: Corn bran is the coproduct of corn wet milling operations with lower commercial value mostly used as animal feeds. They are rich sources of dietary fiber and phenolics. In this research, the effect of two physical modifications of corn brans (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. All the extruded or ground brans supported the growth of probiotic bacteria. The highest growth rate of 0.64 h-1 and lower population doubling time of 1.09 h was observed for 120°C extruded corn bran of 35% moisture fermented with Bacillus subtilis when compared to the control. The total phenolic content was in the range of 9-10 mg GAE/ g of modified brans and was not significantly different from the respective control. Similarly, antinutritional compounds such as phytic acid and trypsin inhibitors were reduced by a maximum of 42% and 34% respectively when extruded and fermented. In summary, the extrusion and fermentation of corn bran positively influenced the non-nutritive compounds, thereby improving their nutritional quality and usage in food applications.