Analysis of relationship between head rice yield and breaking force of Japonica rice grains at different maturity stages

Abstract

Maximum head rice yield is related to the optimal harvest time or moisture content during rice maturity. The physical properties of rice grains, such as the breaking forces, changed with the increasing degree of rice maturity. Harvest moisture content, breaking forces for the dorsal and ventral sides of the brown rice kernel in a three-point bending test and the milling quality properties of rice at different maturity stages were investigated. The relationships between head rice yield and harvest moisture content and also between head rice yield and the breaking forces for the dorsal side and ventral side were analysed. The breaking forces for the dorsal side and ventral side increased at 30/37 and at 44/51 days after heading and decreased at 58/65 days after heading, the increasing and decreasing extent of the breaking force for the ventral side was larger than that for the dorsal side. The breaking force for the ventral side was larger than that for the dorsal side during the maturity period. Head rice yield increased at 30/37 and at 44/51 days after heading, but head rice yield decreased at 58/65 days after heading. The breaking force for the ventral side increased by 9.52, 10.13, 8.59, and 7.33 N, head rice yield increased correspondingly 38.7, 30.7, 34.7 and 15.3% during maturity for different varieties. The moisture content at optimal harvest time with the maximum head rice yield and maximum breaking force for ventral side or dorsal side was 25-30%.