Effects of High-power Ultrasound on the in vitro digestibility, Physicochemical and Functional Properties of Proso Millet Prolamin and Glutelin Proteins

The effect of a high-power ultrasound (50, 75, and 100% amplitude) of 29.29, 38.08, and 52.72 W power levels on selected physicochemical, functional, and in vitro digestibility of two proso millet protein fractions (prolamin and glutelin) for 5 and 10 min was investigated. The protein was extracted from two proso millet cultivar (dawn and Plateau). The results show that the solubility and digestibility of the prolamin and glutelin fractions were significantly (P < 0.05) enhanced as compared to the native protein fractions. On average, about 30, 58, 55, and 28% increase in in vitro digestibility. Similarly, the solubility increased with increasing ultrasound power and treatment time for the protein fractions. For instance, there was a 169, 191, 235% increase in solubility over the native fraction for Dawn prolamin for power levels of 29.29, 38.08, and 52.72 W at 5 min. treatment time. The foaming capacity was observed to only increase significantly with a long treatment time for both the prolamin and glutelin fractions while the emulsion activity index was observed to increase slightly after 5 min of ultrasound treatment but not after 10 min of treatment. The multi-modal distribution of the particle sizes of the proteins could explain the differential behavior in its foaming and emulsion functionality. This study established ultrasound treatment as a method for modifying functional properties of proso millet proteins.