Vacuum‐assisted extrusion of red rice ( bao‐dhan ) flour: Physical and phytochemical comparison with conventional extrusion

Abstract

The effect of vacuum-assisted extrusion cooking on the properties of red rice extrudate was investigated. The rotatable central composite design was employed to determine the effect of independent variables on dependent variables. The process was optimized using an artificial neural network (ANN) and genetic algorithm (GA) The sensitivity analysis of independent variables was conducted and the screw speed showed the highest contribution on the product quality. The optimum condition obtained by ANN and GA was 77.5°C barrel temperature, 32.5% feed moisture, 350 rpm screw speed, and 300 mmHg vacuum level. The developed process was compared with the conventional extrusion process without employing a vacuum in terms of physicochemical and phytochemical properties. The extruded was contented 3.89 mg/L of anthocyanin, 0.021 µm/L of cyanidin-3-glucoside, and 3.21 µm/L of peonidin-3-glucoside. The vacuum-assisted extrusion cooking showed to develop expanded extrudate at low temperatures with higher phytochemical retention. Practical applications Extrusion cooking generally considers as a high-temperature short time process. Due to high temperature and high shear, most of the bioactive compounds are deteriorated during extrusion cooking. Therefore, extruded are considered unhealthy for consumers. The outcome of the present investigation can enhance the retention of bioactive compounds in extruded products. The vacuum-assisted extrusion could expand the extrudate at low temperatures and enhance the retention of bioactive compounds.