The ability of dietary fiber (DF) to bind bile salts (BS) and to modulate lipid digestion contribute to the health benefits of high-fiber foods including reducing hyperlipidemia and hypercholesterolemia. Many studies have focused on the hypocholesterolemic effect of purified soluble DF, like oat -glucans. However, research on the effect of the food matrix and DF microstructure on lipid digestion has received little attention. In addition, few studies have evaluated the binding preferences for individual BS by specific DF fractions due, in part, to the limited separation efficiency of BS mixtures obtained by current methods. The aim of this study is to examine the in vitro BS-binding ability and BS-binding preferences of DF fractions from structurally modified bean matrices, to further evaluate their impact on lipid digestibility. Hydrothermal and high hydrostatic pressure processing were applied to generate different bean (micro)structures. The BS-binding ability of these matrices was determined under physiological conditions by simulating oral, gastric, and duodenal digestion using a mixture of primary BS (NaTC, NaGC, NaTCDC, NaGCDC). Individual unbound BS were quantified separately by reversed-phase HPLC. Different mobile phases, elution gradients, column size and ion pair solvents were compared to optimize the separation efficiency of the BS mixture. The impact of diverse bean microstructures on the extent of in vitro duodenal digestion of extrinsic lipids was further evaluated. Both hydrothermal and pressure treatment affected DF content, fiber fraction distribution, microstructure and rheology of bean matrices which further impacted their capacity to retain BS. The HPLC method using 50% acetonitrile-1% alkyl-tetrabutylammounium-phosphate showed the best separation and recovery of BS. Hydrothermal-treated matrices, with low insoluble fibre and resistant starch content, retained lower amount of BS than pressure-treated matrices, indicating that BS were not directly bound by soluble DF. Preliminary results showed that pressure-treated matrices preferentially retained more hydrophobic di-hydroxy-BS, which decreased the extent of lipid digestion. In this work, a time-efficient, low-cost ion-pair HPLC method was developed to separate a mixture of BS without prior deconjugation and derivatization. This study shows that minimal-processing technologies may enhance the capacity of high-fiber foods to reduce the risk of hyperlipidemia and hypercholesterolemia.

Bile salt binding ability of dietary fiber fractions from structurally modified common bean matrices: Impact on in vitro lipid digestion

2019 Spring National Meeting

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