Progress in tailoring starch intrinsic structures to improve its nutritional value

Starch intrinsic structures significantly influence its digestibility and nutritional attributes. Versatile technologies, including genetic, enzymatic, and physical processes, have been widely used to tailor starch intrinsic structures and, in turn, the digestibility. This review summarizes the current understanding of how conventional modifications affect key intrinsic structures in starch and their underlying mechanisms to regulate the digestibility. It is concluded that densely-packed structures (i.e., short-range ordered structure, helical structure, crystalline structure, and lamellar structures) and highly-branched amylopectin are the key factors affecting starch digestibility. Enzymatic branching treatment significantly increases the content of highly-branched amylopectin for slowing starch digestion. Interaction-reinforcing technologies promote starch reassembly to form helical and crystalline structures, and the ordered aggregated structures result in a reduction in starch digestibility. Interaction-reinforcing techniques include (i) genetically or enzymatically increasing amylose content and elongating amylopectin chain length, (ii) hydrothermal treatment (e.g., heat-moisture treatment, autoclaving, and annealing), and (iii) complexation with non-starchy ingredients (e.g., lipids, proteins, phenolic compounds, and hydrocolloids). With increasing demand for health-promoting foods by consumers and markets, enhanced understanding of starch intrinsic structures and their effects on digestibility after modification will facilitate the development of new products with desired nutritional attributes through starch structuration.