Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: December 1, 2002
Publication Date: December 2, 2002
Citation: Yokoyama, W.H., Knuckles, B.E., Wood, D.F., Inglett, G.E. 2002. Food Processing Reduces Size of Soluble Cereal B-Glucan Polymers Without Loss of Cholesterol-Reducing Properties. American Chemical Society Symposium Series 8:105-116. Interpretive Summary: Cholesterol lowering by oat and barley is attributed to their soluble fiber content. In oat and barley the soluble fiber is called beta glucan. High molecular weight is thought to be preferred and even necessary for cholesterol lowering. Common food processes such as cooking, acidity and stirring can break the polymer strands of soluble fiber. Molecular weights of polymers were determined by laser light scattering analysis. Analysis of molecular weight of beta-glucan polymers from commercially processed oatrim results in polymers about 25% of the original size. Analysis of intestinal contents show beta glucan polymers of about 10% of the original size. Despite fragmentation by food processing beta glucan still reduce plasma cholesterol.
Technical Abstract: Grinding and shear degrade cereal B-glucans but cooking and starch hydrolysis increases extractability and availability of the polysaccharide to interact with digesta in the intestinal lumen. Cereal B-glucans in oat and barley are easily degraded by grain milling machinery and endogenous B-glucanases as shown by size exclusion chromatographic separation of soluble polysaccharides and molecular weight and size characterization by multiple angle laser light scattering. Cooking in water or alkaline solutions extracts B-glucans found mainly in the cell walls of oat and barley grains. Shear generated by stirring or pumping is shown to degrade B-glucans. Animal studies demonstrate that B-glucans that have been reduced in mass by an order of magnitude are still able to reduce plasma cholesterol. Moreover, molecular mass of B-glucan from the stomach and intestine of animals are even lower than the size reduced fiber from processing. These results suggest that overall food processing improves the activity of B-glucans by increasing availability and that polymer molecular mass while reduced is still effective in plasma cholesterol reduction.