Consistency assessment of rice milling quality results from USDA-FGIS official procedures and commercial mills

Background and ObjectivesThe milling quality and grade of rice are typically appraised by milling and inspecting samples collected from a rice lot following US Department of Agriculture (USDA) official procedures using a laboratory mill, which should represent milling quality and grade results of rice milled in commercial mills. The objective of this study was to assess whether the official USDA laboratory mill and procedures provide consistent results with those obtained from commercial mills.FindingsThe results showed that the laboratory mill with the official standard procedures had significantly higher (p < .05) total milled rice yield (TRY) (1.6 percentage points) and head rice yield (HRY) (2.6 percentage points), but lower whiteness index (4.4 units) on average than those of commercial mills. The average TRYs of laboratory-milled rice of long, medium, and short-grain varieties were 1.8, 1.7, and 1.0 percentage points higher than those from the commercial operations. The milling characteristics of pureline and hybrid rice differed between official standard mills and commercial mills.ConclusionIf the rice samples were milled to the same whiteness as the official standard procedures, the TRYs and HRYs could be close to the results from the commercial mills.Significance and NoveltyThis study provides important information that could be used to improve the consistency and accuracy of rice quality assessment of laboratory mills following the official procedures and assure that milling results are comparable to those of commercial milling processes.