Effect of thickness and maturity on protein content of Japonica brown rice collected during postharvest processing

Abstract

The rice industry requires new technologies to increase production in response to world population growth. These include technologies that ensure rice quality in postharvest processing. Protein content defines rice quality and palatability. Differences in kernel thickness and maturity affect the protein level of harvested rice. We therefore analysed the relationship between kernel thickness and maturity on protein content of Japonica brown rice collected during postharvest processing. We fractionated the rice into six thickness fractions and classified each fraction into mature, immature and chalky levels of maturity. Results showed that thickness fraction and maturity level affected protein content. Each increase in thickness produced an increase in the percentage of sound whole kernel and a decrease in protein content. The mature sample had the lowest protein content among maturity levels within each thickness fraction. Based on sound whole kernel and protein content values, we classified the mature sample in higher thickness fractions as having high-quality appearance and palatability. There were significant differences in protein content between different thickness fractions of the mature sample suggested that we can sort rice protein by thickness fraction. Moreover, differences in protein content suggested that we can use the thickness grader and colour sorter machines to sort rice into high or low protein content fractions. This information can contribute to more accurate quality constituent determination through the development of a rice protein sorter. This would support the production of high-quality rice and help address the demand for more efficient technology for rice postharvest processing.