Influence of extrusion cooking on phytochemical, physical and sorption isotherm properties of rice extrudate infused with microencapsulated anthocyanin.

The effect of extrusion cooking on the quality of rice extrudate with infused microencapsulated anthocyanin was investigated. The moisture sorption isotherm of the extrudate was also studied. The rotatable central composite design was used to optimize the extrusion process and the optimized conditions were: screw speed, 121 rpm; barrel temperature, 91.89 °C; and moisture content, 22.03%. The extrudate showed anthocyanin content of 0.218 mg/L; true density, 1.48 g/cc; water activity 0.51, water solubility index, 7.49%; and specific mechanical energy, 31.39 kJ/kg. The antioxidant activity and solubility of the extrudate were higher as compared with native extrudate. The moisture sorption isotherm of the extrudate was found to follow type III isotherm behavior according to the Brunauer-Emmett-Teller classification. The sorption isotherm was analyzed using several models and the Caurie and Peleg models were best fitted with the extrudate isotherm data. The present work manifested a way to develop antioxidant rich extrudate.