Process optimization of rice milling for paddy varieties of Kashmir valley

Physical characteristics and moisture content of local paddy varieties (K-39, Nik china and Jhelum) was measured and operational parameters of rice sheller and polisher were optimized for high yield of head rice. Tri-axial dimensions revealed an average eccentricity index of 1.5, 1.58 and 1.64 conforming bold shape of K-39, Nik China and Jhelum as per ISO classification. The average thickness was 1.60 mm, 1.58 mm and 1.5 mm for K-39, Nik China and Jhelum. The maximum milling efficiency of 86.8% was associated with Jhelum variety with 30% head (brown) rice recovery at sheller clearance of 2.5 mm and 12.3% moisture content. The polishing efficiency varied from 82.9 - 99.4 %, with maximum value related to K-39 variety at 2.0 mm sheller clearance and polisher residence time of 30 seconds. Maximum milling yield of 90.4% was obtained with Jhelum at 2.5 mm sheller clearance and 60 seconds polisher residence time. The degree of milling was maximum with K-39 at 2.0 mm sheller clearance and polisher residence time of 90 seconds. The study can be useful for industrial units and custom based centres to reduce unit cost of rice milling.