Physicochemical and functional properties of proso millet storage protein fractions

The understanding of the protein structure-function relationship is very important to the study of protein chemistry. In this research, the physicochemical, functional, and structural properties of the storage protein fractions from two defatted proso millet cultivars (Dawn and Plateau) were determined and reported. The results show that protein recovery efficiency of 53.5% and 60.1% was recorded for Dawn and Plateau, respectively. The average denaturation temperature of all fractions was about 82.1 ± 3.5 °C. Surface hydrophobicity values for Dawn fractions were 11781, 10594, 316, and 2225 for albumin, globulin, and glutelin, respectively and 3415, 2865, 353, and 456 for Plateau fractions, respectively. Most of the protein fractions showed the highest solubility at pH 9 and lowest solubilities at pH ≤ 7 with solubility range from 5.7 to 100%. Emulsifying activity index (EAI) of less than 0.25 m²/g was recorded for most fractions, while the highest emulsion stability index (ESI) recorded was about 60 min. Prolamin fractions showed three major peptide bands of 11, 14, and 24 kDa while glutelin fraction revealed only a major band of 15 kDa and several minor bands of 11, 22, 24, 78, 209 kDa. No differences in the electrophoresis pattern were observed for the fraction with or without a reducing agent.