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Separation of Water-Soluble Proteins from Cereals by High-Performance Capillary Electrophoresis (HPCE)

¹USDA-ARS, Grain Marketing and Production Research Center, Manhattan, KS 66502. 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. ²Corresponding author. Phone: (785) 776-2725. E-mail: scott@gmprc.ksu.edu.

Most research concerning grain proteins has concentrated on the gluten storage proteins. The albumins and globulins are the water- and salt-soluble proteins that contain biologically active enzymes and enzyme inhibitors. A free-zone capillary electrophoresis method was developed to separate these proteins. Optimization included sample extraction method, capillary temperature, buffer composition, and additives. The optimal conditions for separation of these proteins was 50 μm i.d. × 27 cm (20 cm to detector) capillary at 10 kV (with a 0.17 min ramp-up time) and 25°C. The optimum buffer was 50 mM sodium phosphate, pH 2.5 + 20% acetonitrile (v/v) (ACN) + 0.05% (w/v) hydroxypropylmethyl-cellulose (HPMC) + 50 mM hexane sulfonic acid (HSA). Sample stability was an issue that was addressed by lyophilizing fresh extracts and redissolving in aqueous 50% ethylene glycol and 10% separation buffer. This method was successfully used in both wheat flour and whole meal samples. Comparisons were made of several wheats of different classes as well as several cereal grains. This methodology could be useful in screening cereal grains for important enzymes and their impact on end-use quality such as food functionality, food coloration, and malting quality.