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Development of Standard Procedures for a Simple, Rapid Test to Determine Wheat Color Class¹

¹Cooperative investigations, U. S. Department of Agriculture, Agricultural Research Service (USDA-ARS), and the Department of Grain Science and Industry, Kansas State University. Contribution number 01-173-J, Kansas State Agricultural Experiment Station, Manhattan, KS 66506. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Dept. Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ³USDA-ARS, Grain Marketing and Production Research Center, 1515 College Ave, Manhattan, KS 66502. ⁴Corresponding author. E-mail: fdowell@gmprc.ksu.edu

Growing conditions, kernel characteristics, and genetics affect wheat kernel color. As a result, red and white wheats sometimes cannot be differentiated by visual examination. Soaking wheat kernels in a sodium hydroxide solution enhances the difference in color; red wheat turns a darker red, and white wheat turns straw-yellow. Previously, when NaOH was used for wheat determination of color class, only a visual assessment was made under arbitrary conditions, many times not suitable for field work. In the present work, visible reflectance spectroscopy and visual assessments were used to optimize NaOH (2 mL/g of wheat) soak time (10 min), concentration (5M or 20%), and temperature (60°C). The optimal procedure will provide users who are not laboratory trained with inexpensive, safe procedures to definitively assign wheat color class in the shortest time in field locations. Calibration and prediction of several wheat cultivars using partial least square regression were used to validate the optimal test procedure. The test differentiated even rain-bleached wheat and cultivars that were difficult to classify visually. No distinct correlation occurred between predicted color value and the number of red genes.