Improved bioaccessibility of phenolics and antioxidant activity of glutinous rice and its fermented Chinese rice wine by simultaneous extrusion and enzymatic hydrolysis

The effect of simultaneous extrusion and enzymatic hydrolysis on the phenolics and antioxidant activities of glutinous rice and further fermented Chinese rice wine was investigated. Great modification on rice properties (water absorption/solubility index) related to higher total phenolic content (TPC) retention (87.73%) was determined in enzymatically extruded rice compared to traditionally cooked or extruded rice (37.61-50.85% TPC retention). A total of ten phenolic acids (in free/bound forms) with great loss rates were identified in different treated rice, except the enzymatically extruded rice showing effective inhibition of phenolics loss (only 2.66, 2.04, 22.49, 1.89 and 6.37% loss for total gallic, chlorogenic, vanillic, syringic, and ferulic acids, respectively). After fermentation, the level of p-hydroxybenzoic and p-coumaric acids increased predominantly, while chlorogenic acid dramatically decreased to an extremely low level, indicating a changed chemical proportion of phenolics in Chinese rice wine. Compared with raw rice, enzymatically extruded rice achieved a higher antioxidant activity (DPPH, ABTS, reducing capacity and FRAP), probably due to the synergy of phenolic retention and Maillard-derived products formation. Moreover, this advantage of simultaneous extrusion and enzymatic hydrolysis could be further exhibited in Chinese rice wine products via fermentation processing.