ARS | Publication request: Structure and Functional Properties of Sorghum Starches Differing in Amylose Content

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 2008
Publication Date: July 16, 2008
Citation: Sang, Y., Bean, S., Seib, P.A., Pedersen, J.F., Shi, Y. 2008. Structure and Functional Properties of Sorghum Starches Differing in Amylose Content. J of Agric Food Chem. 56:6680-6685.

Interpretive Summary: Starch was isolated and studied from a waxy, heterowaxy, and normal sorghum to determine their chemical properties. The properties of starch greatly influence their functionality and nutritional properties and therefore waxy and heterowaxy sorghum starch may have unique functionality. Cooked waxy starch was found to behave like a visco-elastic liquid, which differed from that of cooked normal and heterowaxy starch. Heterowaxy starch was found to have less amylopectin chains with a degree of polymerization in the range of 6-15 than did normal starch. Functionally, heterowaxy starch had a higher gelatinization temperature and contained lower amounts of rapidly digestible starch and higher levels of resistant starch than waxy starch.

Technical Abstract: Sorghum is an important cereal grain due to its drought-resistance and relative low cost. Starch is the major component of grain sorghum, and comprises ~70% of dry grain weight. Many important physicochemical, thermal, and rheological properties of starch are influenced by the ratio of amylose and amylopectin, the two major polymers in starch granule, and the structure of amylopectin. In this study, amylose content, gelatinization, retrogradation, paste properties, gelling properties, in vitro enzyme digestion, and amylopectin chain-length distribution of starches from waxy, heterowaxy and normal sorghum were analyzed. Heterowaxy and waxy starch amylopectin had a higher proportion of branch chains with DP >24, therefore a higher gelatinization peak temperature than normal starch. Heterowaxy starch contained significantly lower rapidly digestible starch (RDS) and higher resistant starch (RS) than waxy starch.