Abstract
Interference of dietary fibres with the enterohepatic circulation of bile acids is proposed as a mechanism for lowering cholesterol. We investigated how lupin hull and cotyledon dietary fibres interact with primary bile acids using an in vitro model under simulated upper gastrointestinal conditions. Cell wall polysaccharides were isolated and extracted to separate pectin-like, hemicellulosic, and lignocellulosic structures. Lupin hull consisted mainly of structural components rich in cellulose. The viscosity of the in vitro digesta of lupin hull was low, showing predominantly liquid-like viscoelastic properties. On the other hand, lupin cotyledon fibre retarded bile acid release due to increased viscosity of the in vitro digesta, which was linked with high contents of pectic polymers forming an entangled network. Molecular interactions with bile acids were not measured for the hull but for the cotyledon, as follows: A total of 1.29 µmol/100 mg DM of chenodesoxycholic acids were adsorbed. Molecular interactions of cholic and chenodesoxycholic acids were evident for lignin reference material but did not account for the adsorption of the lupin cotyledon. Furthermore, none of the isolated and fractionated cell wall materials showed a significant adsorptive capacity, thus disproving a major role of lupin cell wall polysaccharides in bile acid adsorption.
Highlights
As a sustainable alternative to soybean products, interest in the inclusion of sweet lupins in food is growing [1]
We investigated how bile acid interactions were influenced by the cell wall polysaccharides of lupin hull and cotyledon
Lupin hull mostly consisted of cellulosic polymers, which is in line with low bile acid retardation induced by viscosity
Summary
As a sustainable alternative to soybean products, interest in the inclusion of sweet lupins in food is growing [1]. Dietary fibres are mainly plant cell wall polysaccharides, such as celluloses, hemicelluloses, and pectin. They are characterized by their resistance to enzymatic degradation in the upper gastrointestinal tract, varying in their structural and nutritional properties [3,4]. Lupin kernel fibres—in contrast to insoluble cereal fibres—have a smooth texture, a neutral taste, and a white colour. This makes lupin kernel fibres an excellent non-intrusive ingredient for fibre enrichment, which shows high palatability and sensory acceptability in dietary interventions [5]
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