Insights on the structure and digestibility of sweet potato starch: Effect of postharvest storage of sweet potato roots

To unravel changes in the structures and digestibility of sweet potato starch in the roots during postharvest storage (0 to 20 days), starches are isolated and characterized in terms of amylose content, polyphenols amount, molecular molar mass (Mw), molecular reassociation and multi-scale reassociated structures after cooking. Results reveal that starch digestibility decreases with a concomitant increase on resistant starch (RS) fraction during the first 10 days. These changes are associated with an increase of ordered structures, amylose and polyphenols content as well as the starch fractions with molecular weight of (2.0-2.5) x 10(7) g/mol. However these trends get reversed at higher postharvesting periods. Correlation matrices reveal that the short-range ordered structures and starch molecular reassociation behavior of starch paste and polyphenol content are the key factors in determining the RS content. Besides, the short-range ordered structures, specific starch molecular weight distribution and amylose of starch paste can be tailored for modulating the digestibility by controlling the postharvest storage time. This study opens a promising pathway to tailor starch digestibility via simply controlling the postharvest storage time of starch-containing crops.