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United States Department of Agriculture

Agricultural Research Service

Title: Separation of Water Soluble Proteins from Cereals by Free Zone Capillary Electrophoresis (Fzce)

item Bean, Scott
item Tilley, Michael

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2003
Publication Date: September 1, 2003

Interpretive Summary: Cereal grains are important human and animal foods. The proteins in these grains serve important functional and nutritional roles. The grain proteins can be divided into several classes based on their solubility in different solutions. One class of proteins, the storage proteins, are known to be very important in the functionality of cereal based foods. Because of this, the storage proteins of grains are the most widely studied type of grain proteins. However, the albumin and globulin classes of proteins, which are extracted with water or salt solutions, can also have important roles in food quality. These proteins are enzymes and can influence pre-harvest sprouting, malting quality, discoloration of food products, and have been related to health problems such as baker's asthma. Therefore, new methods are necessary to study these proteins. This paper reports on new methods to study these proteins and was successfully applied to all of the major cereal grains, including wheat and sorghum. This methodology will be beneficial to scientists and plant breeders working to improve the end-use quality of cereal grains and may be used as a quality screening tool in the future.

Technical Abstract: Most research concerning grain proteins has concentrated upon 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 found to be 50 um i.d. x 27 cm (20 cm LD) 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 re-dissolving 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.

Last Modified: 4/16/2014