Effect of Pre-Heating on Enhancing the Anti-Digestive and Antioxidant Properties of Curcumin Rice by Self-Emulsifying Technology

Abstract

Self-emulsifying delivery systems (SEDSs) generate micro/nanoemulsions within the gastrointestinal tract, enhancing the bioavailability of hydrophobic phytochemicals. Turmeric rice is a staple across Asia, yet the mechanism of curcumin binding with rice remains unclear. This study utilized curcumin SEDS and pre-heating to produce curcumin instant rice (CIR). The CIR maintained its appearance and increased the levels of slowly digestible starch to 26.43–28.38% following steamer steaming (SST). In contrast, cooker water-boiling treatment (CWBT) enhanced resistant starch (16.73–38.24%), curcumin loading (3.77–61.39 mg/100 g), total phenolic content (23.09–193.79 mg GAE/100 g DW), and antioxidant activity. Following 50 min of CWBT, the gelatinization process disrupted the ordered structure of starch, facilitating the formation of amylose–lipid complexes. This process resulted in a maximum resistant starch content of 47.81% and a curcumin loading of 66.50 mg/100 g. Differential scanning calorimetry revealed an endothermic peak for type II crystals (105–130 °C), while X-ray diffraction exhibited V-type patterns, confirming the observed changes. Pre-heating enhanced the curcumin encapsulation and RS of CIR, thereby enhancing its bioavailability relative to conventional turmeric rice.