| | Nutraceuticals are natural, bioactive chemical compounds that have health-promoting, disease-preventing or medicinal properties. Barley grains contain nutraceuticals such as beta-glucan (2-8%, w/w) and tocols (80-120 mg/kg, w/w). Beta-glucan, a non-starch water-soluble polysaccharide (soluble dietary fiber), exists primarily in the cell walls of endosperm and in bran layers of barley grains. Regular consumption of beta-glucan benefits human health (lowers blood serum cholesterol, regulates blood glucose levels and stimulates immune system). In addition, barley beta-glucan is an excellent hydrocolloid (polymers that show high affinity to water) that exhibits thickening and emulsion-stabilizing properties, which are highly desirable in functional food development. Tocols are the family of vitamin E compounds that have been demonstrated to be anticarcinogenic (due to their antioxidant action) and have LDL-cholesterol lowering properties. Because of the aforementioned health benefits, the commercial interest to use barley grains for extraction/concentration of beta-glucans and tocols is growing rapidly.
The beta-glucan molecule is composed of ß-D-1-3 and 1-4 glycosidic linkages. Approximately 90% of the molecule is composed of ß1-4 linked cellotriosyl and cellotettriosyl regions connected with ß1-3 bonds. The literature reports structural diversity and a wide range of molecular weights in barley beta-glucan (5x105 – 1.5x106 Da.) primarily due to variations in the source/genotype and techniques employed for purification and molecular sizing. Tocols belong to two groups of compounds, tocopherols and tocotrienols, each of which has four isomers (alpha, beta, gamma and theta). They are lipid soluble grain components and are concentrated in the bran layers of barley grains. Among the cereal grains, barley contains relatively higher amounts of Tocols, especially alpha-tocotrienol, which exhibits LDL-cholesterol lowering properties.
The presentation will focus on the molecular size and structural diversity of cereal beta-glucans and tocols, the technologies currently available for extraction/concentration of these valuable grain components, and the challenges encountered in the industrial utilization of the extracted products.
Dr. Thava Vasanthan
Associate Professor, Grain Science and Technology
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
Presented at the 3rd Canadian Barley Symposium, June 19-20, 2003 |
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