Use of objective imaging systems to assess subjective grain appearance traits important to the USA rice industry

Authors: McClung, Anna; Chen, Ming Hsuan; JODARI, FARMAN - Rice Experiment Station - California; FAMOSO, ADAM - Louisiana State Experiment Station; ADDISON, CHRISTOPHER - Louisiana State Experiment Station; LINSCOMBE, STEVEN - Louisiana State Experiment Station; OTTIS, BRIAN - Ricetec, Inc; MOLDENHAUER, KAREN - University Of Arkansas; WALKER, TIMOTHY - Horizon Ag-Products, Lp; WILSON, LLOYD - Texas Agrilife Research; MCKENZIE, KENT - Rice Experiment Station - California

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2019
Publication Date: 12/18/2019
Citation: McClung, A.M., Chen, M., Jodari, F., Famoso, A.N., Addison, C.K., Linscombe, S.D., Ottis, B.V., Moldenhauer, K.A., Walker, T.W., Wilson, L.T., Mckenzie, K.S. 2019. Use of objective imaging systems to assess subjective grain appearance traits important to the USA rice industry. Cereal Chemistry. https://doi.org/10.1002/cche.10251.
DOI: https://doi.org/10.1002/cche.10251

Interpretive Summary: Milled rice grain appearance traits, including grain shape, grain uniformity, grain color, and grain translucency (i.e. the opposite of grain chalkiness), determine its grade, price and marketability. These grain traits are evaluated subjectively in the USA by officially trained inspectors and at commercial rice mills. There is interest in determining if digital imaging systems (IS) provide an alternative means to objectively and rapidly measure these traits. This would help producers, buyers, and researchers be assured that rice samples are graded in an efficient and consistent manner. The goals of this study were to compare appearance traits commonly assessed by the USA rice industry as determined visually by inspectors (VI) and using IS and to identify IS parameters that predict VI assessments. Grain chalkiness as determined by commercial mills, a rice exporting company, and government inspectors, differed from results using three IS, WinSeedle, SeedCount and S21. However, all six methods agreed on ranking of the best and worst of 20 US cultivars for chalkiness. This suggests that human assessment of grain chalkiness was less discerning than digital imaging systems. In addition, quality parameters easily and rapidly obtained from the IS were useful in explaining VI ratings of bran streaks, chalk, kernel color, uniformity length and appearance overall as determined by commercial mills. In conclusion, IS can rapidly quantify rice grain appearance traits but agree with subjective ratings for chalkiness only when differences are extreme.

Technical Abstract: Milled rice grain appearance traits, including chalk, determine its grade, price and marketability. These appearance traits are evaluated visually (VI) in the USA by officially trained inspectors and at commercial mills. Digital imaging systems (IS) provide an alternative means to objectively and rapidly measure these traits. The goals of this study were to compare chalk values determined by VI and IS and to identify IS parameters that predict five grain appearance traits commonly assessed by the USA rice industry. Milled rice chalk determined by three VI methods used by commercial mills, a rice exporting company, and government inspectors, and three IS, WinSeedle, SeedCount and S21, differed significantly. However, all six methods agreed on ranking of the best and worst of 20 US cultivars for chalkiness. Multiple linear regression analyses identified quality parameters from each IS that partially predicted the rating of rice quality traits – bran streaks, chalk, kernel color, uniformity length and appearance overall as determined by commercial mills. In conclusion, IS can rapidly quantify rice grain appearance traits but agree with subjective ratings for chalkiness only when differences are extreme. IS demonstrated that discolored kernels and grain chalkiness are the major factors explaining differences in overall appearance of USA long grain varieties as subjectively assessed by commercial mills.