Extrusion-induced pre-gelatinization and hydrolyzation of rice adjunct contributed to the mashing performance

Abstract

The rice extrudates obtained by varying feed moisture were used to evaluate the relationship between the mashing efficiency and physicochemical properties of adjuncts, including functional, rheological, pasting, and structural features. The RVA, XRD, FTIR, and rheological properties of broken rice flour and rice extrudates showed that extrusion weakened the relative viscosity and the ordered structure of starch. SEM demonstrated that the aggregated granules were destroyed by extrusion and led to the loosened internal structure. These changes increased the hydration degree, facilitated starch hydrolysis, and enhanced the reducing sugar content and wort extract yield by 21.12%–28.68% and 2.21%–7.89%, respectively. The Pearson correlation analysis indicated that the properties, including the degree of gelatinization, water absorption ability, pasting properties, and the ordered structure of adjuncts, were significantly correlated to the mashing performance. The extrusion pretreatment was an effective method for simplifying the procedure and improving the efficiency during the mashing stage.