Functionality, in Vitro Digestibility and Physicochemical Properties of Two Varieties of Defatted Foxtail Millet Protein Concentrates

Two varieties of foxtail millet protein concentrates (white and yellow) were characterized for in vitro trypsin digestibility, functional and physicochemical properties. Millet protein concentrate was easily digested by trypsin in vitro. Essential amino acids were above the amounts recommended by the Food Agricultural Organization/World Health Organization (FAO/WHO/UNU) for humans. Yellow millet protein concentrate (YMPC) possessed the highest differential scanning calorimetry result (peak temperature of 88.98 °C, delta H = 0.01 J/g), white millet protein concentrate (WMPC) had the lowest (peak temperature 84.06 °C, delta H = 0.10 J/g). The millet protein concentrates had molecular sizes around 14.4 and 97.4 kDa. They have U-shape solubility curves. Water-binding capacity was in the range of 5.0 and 7.0 g/g, while oil absorption capacity ranged between 4.8 and 5.9 g/g. WMPC had higher bulk density (0.22 g/mL) and emulsifying capacity than YMPC and Soy Protein Concentrate (SPC). Foam capacity and foam stability ranged from 137 to 73 g/mL for WMPC, from 124 to 61 g/mL SPC and from 124 to 46 g/mL for YMPC. Millet protein concentrates are potential functional food ingredients.