Effects of phosphate salts on extrusion behaviour of rice

Abstract

A study on the effect of addition of Na 2HPO 4, and NaH 2PO 4 with a change of process variables, on the extrusion behaviour of rice grits, was made. The extruder die pressure and specific energy consumption (SEC) and extrudate properties such as expansion, density, water absorption and water solubility indices, aqueous dispersion viscosity, before and after cooking, and shear-thinning index were analysed. Second order polynomials were used to model extruder parameter and product characteristics. Addition of NaH 2PO 4 to rice grits decreased die pressure, SEC of extruder and expansion of extrudates, and increased water absorption and solubility indices and aqueous dispersion viscosities of extrudates. Na 2HPO 4 also showed a similar effect on die pressure, SEC of extruder and expansion of extrudates whereas the reverse was observed for water absorption and solubility indices and aqueous dispersion viscosities of extrudates.