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Functionality of Barley Proteins Extracted and Fractionated by Alkaline and Alcohol Methods

¹Dept. Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5. ²China University of Geosciences, Wuhan, PRC 430074. ³Corresponding author. Phone: +1-780-492-0038. Fax: +1-780-492-4265. E-mail: lingyun.chen@ualberta.ca

This research optimized the extraction of different protein fractions from barley grains and assessed the physicochemical properties of the fractions obtained. Pearling was first used to remove the grain's outer layers (mainly bran and germ) so that the barley cytoplasmic proteins (albumin and globulin) would be enriched in the pearling flour (PF), while endosperm proteins (hordein and glutelin) would be enriched in the pearled grain flour (PGF). Salt, alcohol, and alkaline solutions were then used to extract different barley protein fractions from PF and PGF. The effects of extraction solvent type, pH, temperature, and extraction time on protein content and extraction efficiency were studied. Aqueous ethanol (55%, v/v) efficiently extracted barley hordein from PGF at 60°C, whereas pH 11.5 alkaline solution was the most efficient for extracting both cytoplasmic and endosperm proteins from barley PF and PGF at 23°C. Subunit molecular weight, amino acid composition, and the functional properties of each isolated barley protein fraction were investigated. Barley glutelin demonstrated superior oil-binding property and emulsifying stability, whereas barley hordein exhibited good foaming capacity.