Mechanism of feruloylated oligosaccharides from rice bran in reversing the rapid digestibility of thermally processed rice starch.

Thermal processing is unavoidable in daily diets. However, most thermal processing treatments accelerate rapid starch digestion. In this study, four common thermal processing treatments including boiling, steaming, microwave, and baking were employed. Using spectroscopic, microscopic, and digestion kinetic techniques, we systematically revealed the change of rice bran-derived feruloylated oligosaccharides precipitated with 90% ethanol (90%RBFOs) on the structure and digestibility of rice starch (RiS) during thermal processing. The results showed that all thermal treatments disrupted the RiS granular structure, with steaming and microwave treatments causing the pronounced damage. 90%RBFOs interacted with RiS to form aggregates, which hindered the contact between RiS granules and water molecules, suppressed granule swelling, and thereby alleviated the structural destruction induced by thermal processing. In vitro digestion experiments further demonstrated that thermal processing significantly increased the digestibility of RiS, while 90%RBFOs markedly reduced the hydrolysis rates of the aggregates to 89.04 ± 0.32%, 83.60 ± 0.62%, 84.54 ± 0.67%, and 77.26 ± 0.75%, respectively. Furthermore, 90%RBFOs increased the total content of slowly digestible and resistant starch in the aggregates by 3.84%, 7.24%, 14.26%, and 4.22%, respectively. Notably, 90%RBFOs have the potential to counteract rapid starch digestion.