Influence of chemical and physical modification on the bile acid binding capacity of dietary fibre from lupins (Lupinus angustifolius L.)

Bile acid adsorption by dietary fibre in the human intestine is widely considered to be a mechanism for lowering the blood cholesterol level and reducing the risk of colon cancer. In this study, the influence of physical and chemical treatment on the bile acid binding capacity of lupin dietary fibres was determined in vitro. Various methods for modifying dietary fibres were investigated (enzymatic, acid, and alkaline hydrolysis, as well as acetylation). The bile acid binding capacity was measured using an enhanced in vitro digestion model. The native lupin fibre product showed a bile acid binding capacity of 19%, whilst the medication cholestyramine exhibited a binding capacity of almost 100%. Enzymatic and acid hydrolysis caused a significantly increased binding capacity of up to 38%, corroborating the importance of dietary fibre structure, composition, and degree of degradation as determining factors for the bile acid binding capacity. The results of the acetylation experiments support the hypothesis of a hydrophobic linkage between bile acids and dietary fibre. Furthermore, the binding capacity depends on the particle size distribution, and consequently on the particle specific surface area.