Alkali spreading value and Image Analysis

Since its first appearance, the alkali test has been extensively employed in rice quality studies as an indirect estimation of the gelatinisation temperature and the cooking quality. Nevertheless, the modifications brought to this method during the years focused on the experimental conditions of the test without taking into account the subjective interpretation of the results. The aim of this study was the search for a reasonable substitute for the human visual decision-making process implicated in the alkali test and, in particular, for a digital image analysis method involving the use of a flatbed scanner (easy to use and available at low cost) to quantitatively measure the degree of dispersion of rice kernels during the test. Significant correlations were found between a new index, the rice kernel disintegration area, obtained from Image Analysis, and the alkali spreading value (r=0.942, P<0.01), the amylose content (r=-0.855, P<0.01) and the micro-visco-amylographic gelatinisation temperature (r=-0.928, P<0.01).