Abstract
ABSTRACTStarch A‐ and B‐type granules were isolated from soft wheat (Triticum aestivum L.) genotypes representing the four granule bound starch synthase I (GBSSI) classes, and characterized according to composition and properties. While total (TAM) and apparent (AAM) amylose contents of both granule fractions decreased as starch waxy character increased, the A‐type granules possessed higher TAM and AAM contents than B‐type granules for a given genotype. From wild‐type to waxy, a general transition was observed from B‐ to A‐type starch granule fractions with higher levels of lipid‐complexed amylose (LAM) and phospholipid. Within a genotype, A‐type (relative to B‐type) granules possessed higher gelatinization enthalpies, while B‐type granules exhibited higher gelatinization peak and completion temperatures (broader gelatinization ranges) than A‐type granules. Normal (wild‐type) and waxy A‐ and B‐type starch granule pasting rates were affected by starch granule lipids; the granule type within a genotype with the lowest LAM and phospholipid levels generally exhibited the shortest time to pasting. For normal and waxy starches, A‐type granules exhibited higher pasting viscosities than B‐type granules throughout the pasting profile. Thus, the A:B‐type granule ratio is important to understanding overall wheat starch composition and behavior.
Published Version
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