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

Calcium lactate (C 6 H 10 CaO 6) 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 C 6 H 10 CaO 6 and other Ca sources (CaCl 2 /CaSO 4) at temperatures ranging from 85 to 105 °C. Rapid visco-analysis and X-ray diffraction showed that the C 6 H 10 CaO 6 -induced bioextrudate had a relatively low viscosity (<200 cP) and crystallinity (7.47%), while SEM revealed a cross-linked porous surface. C 6 H 10 CaO 6 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% (CaCl 2 ≈ C 6 H 10 CaO 6 > CaSO 4), probably reflecting changes in the functional properties and microstructures of the extruded samples. The highest FE value was 89.49% for the C 6 H 10 CaO 6 -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 C 6 H 10 CaO 6 addition. • Broken rice was treated by C 6 H 10 CaO 6 -induced bio-extrusion. • The optimal response of rice with C 6 H 10 CaO 6 , CaCl 2 , CaSO 4 to temperature was 95 °C. • C 6 H 10 CaO 6 extrudate has low viscosity, crystallinity and has a porous surface. • The fermentation efficiencies increased to 86.16–87.95% as CaCl 2 ≈C 6 H 10 CaO 6 > CaSO 4. • The phenolic content and antioxidant activity of CRW were improved by C 6 H 10 CaO 6. [ABSTRACT FROM AUTHOR]