Comparative evaluation of physicochemical and fermentative responses of three sorghum varieties from dryland and irrigated land and the properties of proteins from distillers’ grains

Abstract

Three sorghum varieties [waxy sorghum (WS), high protein sorghum (HPS), and normal sorghum (NS)] grown under dryland and irrigated conditions were evaluated with respect to the physicochemical and fermentative properties. The proteins were extracted from wet distillers' grains with solubles (WDGS) and characterized in terms of purity and in vitro digestibility. Starch, crude protein, crude fat, and fiber contents of the sorghums ranged from 64.16 to 68.05 g/100 g, 11.49–13.54 g/100 g, 2.45–2.98 g/100 g, and 1.62–1.80 g/100 g, respectively. For the same variety, the sorghums grown under dryland conditions had higher protein (0.33–0.91 g/100 g) and lower starch contents (0.74–1.72 g/100 g) than those grown under irrigation conditions. The highest ethanol concentration (85.15 g/L) and yield (41.64 mL/100 g sorghum) were obtained from the NS under dryland conditions and HPS under irrigation conditions, respectively. Sorghums from irrigated land displayed 0.56–8.23 mL/100 g sorghum of ethanol yield higher than those from dryland. Protein (40.21–45.13 g/100 g), crude fat (11.54–13.95 g/100 g), and crude fiber (7.13–9.29 g/100 g) contents in dried distillers' grains with solubles (DDGS) were increased approximately four times compared to the raw sorghum flour. The purity and digestibility in terms of the degree of hydrolysis of the proteins isolated from different sorghum sources ranged from 88.82 to 94.22% and 33.35 to 37.29%, respectively. In addition, the effects of sorghum variety, treatment (dryland and irrigated land), and their interaction on the chemical composition of sorghum and DDGS, ethanol concentration and yield, as well as the purity and digestibility of WDGS proteins were elucidated with a set of correlation coefficients among parameters associated with sorghum.