Relating Rice Kernel Breaking Force Distributions to Milling Quality

Three-point bending tests were conducted to determine the mechanical strength distributions of brown rice kernels.Three long-grain rice cultivars (Cypress, Drew, and XL6) were initially studied. Breaking force (the force required tobreak a brown rice kernel in three-point bending) was not significantly related to kernel width or length. However, there wasa significant correlation between breaking force and kernel thickness; thicker kernels tended to have higher breaking forces.For all three cultivars, kernel-to-kernel breaking force distributions tended to be bimodal: one dominant peak existed around30 N and a smaller peak around 15 N. The data showed that rice samples could have similar average kernel breaking forces,but their breaking force distributions were quite different. In turn, head rice yield was not related to the average breakingforce of rice kernels in a sample; however, head rice yield was closely related to the percentage of strong kernels, definedas kernels that sustained a 20 N force in bending. Based on this apparent finding, the breaking force distributions and headrice yields for seven additional rice lots were measured. A linear relationship was observed between the sample head riceyield and the percentage of strong kernels in the sample.