In Vitro Digestibility of Starch Gel in Cooked Rice Prepared with Thermo-Reversible Short-Chain Glucan Aggregates (SCGAs).

Abstract

To enhance the food applicability of SCGAs, this study investigated the thermo-reversible behavior of SCGAs after cooking and evaluated the in vitro digestibility of starch gels in a real food system, i.e., cooked rice. For the thermo-reversibility of SCGAs, the DSC double-helical melting enthalpy and relative crystallinity of SCGAs decreased after cooking but increased upon cooling. In addition, cooling SCGAs to 30 °C after cooking led to increased slowly digestible starch (SDS) and RS contents associated with a lower glycemic index. These results indicate that cooked SCGAs undergo rapid recrystallization during the cooling process and maintain their resistance to digestion. For application in a real food system, RS content increased with the increasing amount of SCGAs. Furthermore, when the cooked rice was frozen and thawed, the RS content further increased due to the retrogradation of both cooked rice and SCGAs during storage. The appearance and textural characteristics of the cooked rice were not affected by adding SCGAs up to 20%. Nevertheless, the addition of SCGAs to the rice positively increased SDS and RS contents as well as reducing the estimated glycemic index (eGI), indicating low digestibility of starch gels. Consequently, SCGAs exhibited unique thermo-reversibility and low digestibility, which could be applied to real food systems. Overall, this study highlights the potential of SCGAs as a functional material for a wide range of thermally processed starch gel foods.