Relationship between the degree of milling, ash distribution pattern and conductivity in brown rice

Four Indian rice cultivars differing in their shape (length–breadth ratio) were evaluated for ash distribution pattern using a McGill No.2 rice miller. Brown rice obtained from all rice cultivars was milled for 10, 20, 30, 40 and 50 s and analysed for ash content, conductivity and percentage of bran removed. All the cultivars differed significantly with respect to percentage loss of ash content at various milling stages. Cultivars with lower length–breadth ratio showed a higher loss of ash than those having a higher length–breadth ratio under similar stages of milling. Ash content showed a linear relationship with conductivity of solubles extracted from brown rice milled for different intervals. R2 values, for (the relationship between ash content determined by standard AACC method and the conductivity, was in the range of 0.90–0.99. The effect of extraction time and temperature on the relationship between ash content and conductivity of solubles was also studied. Statistical analysis showed a significant effect of extraction duration and extraction temperature on the intercept and slope values obtained from linear regression between ash and conductivity values for different cultivars.