Distinctive characteristics of A- and B-type starch granules in high-amylose wheat: A comprehensive analysis of morphology, structure, and digestibility

Abstract

This study compared the properties of A- and B-type starch granules isolated from non-GMO high-amylose wheat with those from normal and waxy wheat. The focus was on morphological, molecular structural, crystalline, pasting, thermal, and digestible aspects. A- and B-type granules of high-amylose wheat starch (starch H) exhibited distinct morphological features, appearing more elongated with higher amylose content and longer amylopectin branch chain length compared to those of normal and waxy wheat starch (starch N and W). This led to different crystalline patterns and thermal properties. The pasting properties of A- and B-type granules in starch H displayed a unique viscosity pattern, indicating slower and insufficient swelling for A-type than B-type granules, which was an opposite trend to those in starch N and W. Although A-type granules of all starches exhibited slower digestion rates with smaller rapid digestible starch content and larger slowly digestible starch content than their B-type counterparts, starch H exhibited significantly greater resistance to digestion, resulting in higher resistant starch content, particularly for A-type granules, influenced by their molecular structural properties. Overall, this study provides insights into the unique characteristics of high-amylose wheat starch granules based on molecular structure and in vitro digestibility.