Ultrasound pretreatment on soluble dietary fiber-polyphenol from lotus root: Preparation, interaction, and characterization

Complexation with phenolic compounds affects the composition and functionality of soluble dietary fiber (SDF) in lotus root, so the specific ultrasound pretreatment was carried out in this study to investigate its impact on the interaction between these polysaccharides and polyphenols (PP). The SDF-PP complex, ultrasound-treated SDF-PP complex (UT/SDF-PP), and their physical mixture (SDF&PP) were respectively prepared and identified. It was found that PP was primarily bound to SDF via hydrogen bonds, the ultrasonication increased the phenolic content in complex by 78.95% but without altering their combination mode. Even though the apparent structure of dietary fibers was changed by ultrasound indicating smoother and flatter, it slightly reduced the molecular weight and the thermal stability of SDF complex. Moreover, in vitro adsorption experiments have demonstrated that ultrasound significantly enhanced the abilities of SDF complex to adsorb lipid and cholesterol. Therefore, it can be conjectured that suitable ultrasound pretreatment has the potent to promote the combination of naturally active compounds in food ingredients and improve their functional properties. • Ultrasound promotes the binding of polyphenols and soluble dietary fiber. • The binding of soluble dietary fiber (SDF) and polyphenols (PP) is a non-covalent interaction, and appropriate ultrasound does not alter the mode of action. • Ultrasound enhances SDF-PP non-covalent to alter physicochemical properties of complexes. • Proper ultrasound reduces the molecular weight of the complex, resulting in a smoother structural surface.