Estimating Head Rice Yield of Long-Grain Rice using a Bending Force Instrument
Abstract. Head rice yield is an important index of rice quality. The official procedure for determining head rice yield requires a 1000-g sample of rough rice or a lesser sample of rough rice for a modified procedure. In certain situations, such amounts of rough rice may not be available for conducting an actual milling analysis; thus, there is a need to provide alternative methods of estimating head rice yield using a smaller sample. In this study, a PaddyCheck instrument was used to individually measure the three-point bending strength of approximately 250 rough rice kernels per sample. The instrument then classified the kernels as either “hard,” “soft,” or “broken by a force &amp;lt;17 N” (BBF). Additionally, each kernel was individually illuminated using polarized light as a means of estimating chalkiness. The kernel parameters measured using the PaddyCheck were then used to develop an equation for estimating head rice yield, based upon head rice yields determined using a modified milling procedure. The equation developed could be used in conjunction with the PaddyCheck instrument to provide estimates of head rice yield and thus, might allow the instrument to be more useful to practitioners in breeding programs and others involved in harvesting and drying operations to compare head rice yields of various samples/treatments, where the available rough rice sample or time is not sufficient to conduct an actual milling analysis. Keywords: Breaking force, Head rice yield, PaddyCheck, Rice milling, Rice quality, Rough rice.