Structural, Rheological and Biological Functionality of Fiber-Rich Fractions From Beans
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Abstract
egumes have been reported as a good source of dietary fiber. This research aimed to understand how soluble dietary fiber (SDF) can be extracted from dry beans to enhance human health. Raw bean samples were ground with a hammer-type mill. Cooked bean samples were boiled to their optimum cooking time, freeze-dried, and ground. Phenolic content was measured by Folin-Coilteau reaction. SDF was extracted by enzymatic digestion (α-amylase, protease, & amyloglucosidase), filtration, SDF flocculation with 95% (v/v) ethanol and freeze-dried. High-Performance Size Exclusion Chromatography (HPSEC) and high-performance anion-exchange chromatography (HPAEC) were used to study SDF composition. Flow behavior was measured at various SDF solution concentrations (2%, 4%, 6% w/v). Immunomodulatory properties were studied in vitro by quantifying the levels of selected cytokines released by RAW264.7 cells (macrophages) when treated with SDF. The impact of macrophages conditioned media (MCM) treated with the SDF on 3T3-L1 adipocyte (fat) cells differentiation (adipogenesis) was assessed. The results showed that cooking processing significantly (p < 0.05) reduced flour phenolic content and antioxidant capacity. The SDF-rich fractions monosaccharide composition indicated the presence of pectic polysaccharides, hemicelluloses and raffinose family of oligosaccharides (RFOs). The SDF molecular weight distribution showed a significant (p < 0.05) reduction of low molecular weight (LMW) fractions after the cooking process. In contrast, the high molecular weight (HMW) fractions were not affected by cooking. Studied SDF solutions were highly viscous, but the viscosity was lost when shear force was applied, thus exhibiting a shear-thinning behavior. For the immunomodulatory properties, the results indicated that the extracted SDF caused a pro-inflammatory response, suggesting its potential use as an immune system stimulator. Regardless of the SDF sample, when TLR-4 signaling inhibitor was added, cytokines production was significantly (p < 0.05) decreased, suggesting the affinity of SDF with the TLR-4 receptor. Finally, a significant (p < 0.05) decrease in lipid accumulation and reduced protein expression of adipogenic markers was detected from adipocytes cultured with MCM treated with SDF. The results suggested that the SDF extracted from dry beans has the potential to reduce adipogenesis and could be used as food supplements to reduce or prevent obesity.