Extrusion behaviour and product characteristics of brown and milled rice grits

Abstract

Extrusion behaviour of milled and brown rice grits obtained from six rice cultivars (Jaya, IR-8, PR-103, PR-106, Pusa No.1 and Basmati 385) was investigated using Brabender single screw extruder. Feed moisture of the grits was adjusted to 16%, and extrusion cooking was done at barrel temperature of 150°C and screw speed of 100 rpm. The milled and brown rice grits from different rice cultivars differed significantly with respect to extrusion behaviour and extrudate characteristics. Extrudates obtained from milled rice grits showed higher die pressure, expansion, water absorption index (WAI) and water solubility index (WSI) as compared to those from brown rice. WSI of extrudates varied from 3.38 to 10.5%, WAI from 5.20 to 6.90, die pressure from 6068 to 9325 kPa and expansion from 7.52 to 11.30 respectively. The grits from cultivars which had lower length-breadth ratio and mealy endosperm resulted into more expanded extrudates and hence were found to be more suitable from extrusion.