Aggregation and microstructure of cereal β-glucan and its association with other biomolecules

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A plethora of studies have shown the ability of cereal dietary fiber to improve intestinal health and to protect the colon from diseases. Lowering of blood cholesterol levels and a reduced risk of coronary heart diseases are just examples for beneficial health effects often directly related to β-glucan from cereal grains. β-Glucan is one of the major components of dietary fiber and is found with highest abundance in oat and barley. Yet, although intensively studied, there is no definitive theory on the mechanisms of β-glucan during human digestion established. It was suggested that its solution and aggregation behavior, in addition to its ability to form viscous slurries in the gut, govern the claimed beneficial health effects. Therefore, attempts have been made to investigate extracted β-glucan to improve current knowledge concerning the aggregation and solution behavior of β-glucan found in food products.β-Glucan was found to have high molar masses and large sizes. A combination of several analytical techniques showed the presence of highly aggregated structures in a widely distributed, loose β-glucan network. Barley β-glucan showed, in addition, surprisingly well-defined and dense aggregates. There were no proteins covalently bound to the β-glucan, but a direct relation between proteins and β-glucan was found suggesting electrostatic interactions to play an important role during aggregation. During in vitro gastric and gastrointestinal digestion studies, digestive enzymes were not found to have any impact on β-glucan conformation. Nevertheless, bile acids showed a molecular interaction with β-glucan from oats able to cause a reduction in blood cholesterol.