Physicochemical properties of wheat starches and their relationship to liquefaction and fermentative bioethanol performance

Abstract

Fourteen varieties of wheat grown in western Canada were assessed for differences in starch content and structure. Physicochemical properties of starch such as amylopectin to amylose ratio, starch granule morphology, and thermal and pasting properties were all found to vary significantly between varieties. Enzymatic susceptibility was measured using industrial α-amylase to hydrolyze gelatinized starches and resultant reducing sugar content ranged from ~407−500mg glucose equivalents per gram starch, indicating different patterns of oligosaccharide chain lengths present after hydrolysis. During fermentation striking differences in glucose generation were observed, the high glucose cohort averaged 1.21 g/g-starch for the initial time point, compared to a range of 0.83−1.05 g/g-starch for the low glucose cohort. In general, the pattern of glucose generation appears to be consistent with ethanol and biomass production. Correlating structural attributes with fermentation performance suggests that amylopectin to amylose ratio is the most predictive factor in the pattern of wheat starch hydrolysis.