DIFFERENCES IN STARCH COMPOSITION AND PHYSIOCHEMICAL PROPERTIES ARE INFLUENCED BY GRANULE TYPES IN WHEAT AND ITS RELATIVES

Abstract

Starch morphology, composition, and physiochemical properties were characterized from wild wheat species and wheat cultivars with diploid (AA, BB, and DD genome), tetraploid wheat (AABB genome), and hexaploid (AABBDD) genomes. The A-type and B-type granules were separated and purified from each wheat genotype. Starch size, distribution, amylose content, distribution of amylopectin chain lengths, gelatinization, and retrogradation were analyzed in different wheat genotypes. Our results indicate that Aegilops speltoides (BB genome) has a significantly higher percentage of large A-type granules. The A-type granules contained significantly higher amylose content than the B-type granules in all accessions. Amylopectin exhibited more B2 and B3 chains (DP 25 and up) but less A chains (DP 6-12) in the A-type than the B-type granules. The extent of enthalpy changes during starch gelatinization was greater and retrogradation rates were higher in the A-type than the B-type granules. However, the B-type granules have broader ranges of gelatinization temperatures (Tc–To) than the A-type granules. Additionally, the B-type granules of wild diploid species (AA and BB genome) consistently exhibit lower onset (To) and higher peak (Tp) and conclusion (Tc) temperatures. Thus, starch structure is closely related to functionality, and granule size and distribution are significantly correlated to starch thermal properties.