GRAY-SCALE INTENSITY AS A POTENTIAL MEASUREMENT FOR DEGREE OF RICE MILLING

An investigation is reported on the analysis of two factors, depth of sample and field of view, that would affect a measurement system developed for determining the "degree of rice milling" using grey-scale. Traditionally, the degree of rice milling has been determined subjectively through visual inspection by experienced technicians. The concept of grey-scale intensity using machine vision could provide a reliable and objective measurement for quality control. Grey-scale intensity utilizes the variations of light intensities caused when the amount of light passing through a partially translucent milled rice sample is limited by the amount of bran on the rice kernels. The study of two rice varieties produced prediction models between the mean grey level measured in a digitized image and the surface lipids concentration on the rice kernels. The coefficient of multiple determination was 0·84 and 0·67 for the two quadratic regression models. The visual inspection was incorporated into three-way correlation analyses. The mean grey levels could differentiate the three levels of grading done by visual inspection. The optimal depth of rice sample and light intensity to use have yet to be determined. © 1994 Silsoe Research Institute.