Calcium—lactate-induced enzymatic hydrolysis of extruded broken rice starch to improve Chinese rice wine fermentation and antioxidant capacity

Abstract

Calcium lactate (C6H10CaO6) was introduced to improve enzymatic starch hydrolysis in extruded broken rice used for Chinese rice wine (CRW) fermentation. The effects of the extrusion environment (enzyme concentration 0–0.25‰, calcium content 0–4 mmol/100 g, reaction temperature 60–110 °C, screw speed 50–250 rpm) were studied on the activity of thermostable α-amylase, as was the addition of C6H10CaO6 and other Ca sources (CaCl2/CaSO4) at temperatures ranging from 85 to 105 °C. Rapid visco-analysis and X-ray diffraction showed that the C6H10CaO6-induced bioextrudate had a relatively low viscosity (<200 cP) and crystallinity (7.47%), while SEM revealed a cross-linked porous surface. C6H10CaO6 addition (below 95 °C) significantly increased the bioextrudate reducing sugar and water solubility index by approximately 17% and 10%, respectively. Ca addition improved the CRW fermentation efficiency (FE) of the bioextrudate from 82.76% (control without Ca2+) to 86.16–87.95% (CaCl2 ≈ C6H10CaO6 > CaSO4), probably reflecting changes in the functional properties and microstructures of the extruded samples. The highest FE value was 89.49% for the C6H10CaO6-induced bioextrudate when the Ca2+/Mg2+ balance was maintained by adding 1.5 fold of Mg2+. The phenolic content and antioxidant activity of the CRW were also improved (0.94 g GAE/L and 92.5 mg TEAC/L, respectively) by C6H10CaO6 addition.