Abstract:The physicochemical indices and in vitro digestibility characteristics of acorn starch were systematically compared after exposure to dry heat, pre-gelatinization, and heat-moisture treatments. The results showed that acorn starch has a smooth surface, with mainly an elliptic, spherical, and irregular shape, with a particle size distribution ranging from 0.42 to 26.30 μm and a gelatinization temperature of 76.75 ℃. Dry heat treatment caused the migration and removal of water molecules, which did not obviously involve starch gelatinization and retrogradation, and had no significant effect on the physical and chemical indexes such as particle shape, particle size, gelatinization temperature, and A-type crystalline structure of acorn starch. Pre-gelatinization and heat-moisture treatments changed the particle structure and crystallization type of raw starch, and increased the size of starch particles, with a particle size distribution range of 1.26~416.87 μm; starch particles became irregular in shape with a rough surface when the gelatinization temperature was reduced to 50.17 ℃, and ΔH, To, Tp, Tc, and freeze-thaw stability were decreased significantly (P<0.05). The in vitro digestion rates of acorn starch were in the order of dry heat treatment > control treatment > heat-moisture treatment > pre-gelatinization treatment. On the contrary, the content of resistant starch was the highest in the pre-gelatinization treatment (38.21%) and the lowest in dry heat treatment (16.15%). This study provides a reference for the deep processing of acorn starch, which can guide the development of high-quality acorn starch products.
