Flavonoid modification of heat-treated chestnut starch: physicochemical properties and in vitro digestion characteristics.

Chestnut starch has potential for functional foods, but its physicochemical stability and digestibility require improvement. This study investigated the effects of dry heat treatment (100, 160, and 200 °C) combined with 7-hydroxyflavanone, hesperetin, or naringenin on chestnut starch. Compared with temperature-matched controls, flavonoid treatment generally reduced solubility at 100 and 160 °C, increased oil absorption across all temperatures, and decreased gel hardness and chewiness. Flavonoid incorporation increased resistant starch by 13.75-42.60% and reduced rapidly digestible starch by 15-25%. The lowest eGI values were observed with naringenin at 100 and 160 °C and with hesperetin at 200 °C. Structural analyses further revealed differences in particle-size distribution, morphology, FTIR band-intensity ratios, relative crystallinity, and helical conformations. Overall, the magnitude of these responses depended on both flavonoid type and treatment temperature, highlighting the potential of flavonoid-assisted dry heat treatment for tailoring the nutritional functionality of chestnut starch.