Comparison of Milling Characteristics of Hybrid and Pureline Rice Cultivars

Milling characteristics vary among rice cultivars due to inherent differences in physicochemical properties. Hybrid cultivars have gained popularity due to their favorable production performance, but may exhibit different milling characteristics than pureline cultivars. A study was conducted to compare milling characteristics of two long-grain, pureline cultivars (Wells and Francis) and four long-grain, hybrid cultivars [XL723, Clearfield (CL) XL729, CL XL730, and CL XL745]. Rough rice samples of each cultivar were conditioned to 12.5% moisture content (MC) (w.b.) prior to milling, and sub-samples of four cultivars (Wells, Francis, CL XL729, and CL XL745) were conditioned to 10.5%, 11.5%, and 13.5% MC in order to evaluate the effect of MC at time of milling. Samples were milled for durations of 10, 20, 30, and 40 s. Results showed that hybrids generally reached the target surface lipid content (SLC) in a shorter duration than purelines, and that the color of hybrid head rice was generally whiter and less yellow than purelines after milling for any duration. Slopes of head rice yield (HRY) versus SLC, indicating the rate of change in HRY per unit change in SLC, varied significantly among cultivars. Milling MC had an effect on milling curves, in that rice milled at greater MC exhibited lesser SLC values and greater rates of change in HRY with respect to SLC than rice milled at lesser MC. The findings indicate a need to consider SLC in order to equitably compare milling performance and functional properties of different rice cultivars.