Effect of extrusion parameters on the interaction between rice starch and glutelin in the preparation of reconstituted rice

Reconstituted rice produced by extrusion has been attracted attention due to nutritional fortification and convenient production. Nevertheless, how to achieve desirable qualities and physicochemical properties of reconstituted rice nearly to natural rice by regulating extrusion process parameters is difficult. Herein, rice starch/glutelin mixture as raw material of reconstituted rice was extruded at varying extrusion conditions. Specific mechanical energy (SME) and sectional expansion index (SEI) dropped with rise in density (R2 = 0.9117 and 0.8207). Solubility was enhanced with increase in product temperature (R2 = 0.9085), color darkened and shifted to reddish and yellowish as extrusion temperature increased (R2 = 0.8577). These trends were well fitted by sigmoid models. Furthermore, SME enhanced hydrophobic and electrostatic interactions between rice starch and glutelin and caused the reduction in crystallinity and thermal stability, promoting the formation of a bi-continuous matrix of protein aggregates with rice starch. The obtained results can be applied to guide the production of reconstituted rice with desirable qualities.