Effect of synergic pretreatment with ultrasound and alkaline hydrogen peroxide on enzymolysis and physicochemical properties of corn starch

In this study, the effects of three kinds of pretreatments (A1: alkaline hydrogen peroxide pretreatment (6% H2O2, 4 h, 40 °C), A2: ultrasound pretreatment (30 min, 480 W, 40 °C), and A3: synergic pretreatment (6% H2O2, 40 min, 360 W, 40 °C)) on enzymolysis and physicochemical properties of corn starch were investigated. Our results showed that among these three pretreatments, the synergic pretreatment significantly reduced the time to reach the most appropriate dextrose equivalent (15%) value of saccharification in the liquefaction process. In the meantime, the synergic pretreatment also improved the dextrose equivalent value in the saccharification process. The rate constants of synergic pretreated starch were significantly higher than native (8.20 × 10−3 min−1), oxidative (11.3 × 10−3 min−1), and ultrasound starch (12.3 × 10−3 min−1). After pretreatment, the scanning electron micrograph showed significant gaps and pits in the starch granules. Dextrose equivalent value was negatively correlated to viscosity, gelatinization temperatures, enthalpy, the degree of order, the double helix, infrared crystal index, and relative crystallinity (RC), respectively. It was terminated that synergic pretreatment significantly improved reducing sugar yield, reduced the enzymatic resistance, the thermal properties (To, Tc, Tp, ΔH) and RC value in the enzymolysis process of corn starch, and accelerated the enzymolysis process, which provided a new theoretical basis for enzymolysis of corn starch.