Abstract
Interactions between polyphenols and dietary fiber might play an important role in <br /> polyphenol bioactivities. These interactions can be studied through adsorption processes. <br /> The aim of this study was to investigate the adsorption of phenolic acids (p-coumaric <br /> acid, caffeic acid, chlorogenic acid) onto dietary fiber – β-glucan. Adsorption was carried <br /> out at different temperatures (25, 37, and 45 °C) and pH values (1.5, 5.5, and 10). <br /> Non-linear isotherm adsorption models (Langmuir, Freundlich, Dubinin-Radushkevich, <br /> Temkin, Hill) were applied to analyze the data. Experimentally determined adsorption <br /> capacities showed some fluctuations with temperature and pH. Adsorption isotherms <br /> modelled the experimentally determined adsorption capacities well. According to isotherm parameters, it can be suggested that the adsorption was a physical process with <br /> non-covalent bonding at all temperatures and pH. Thermodynamic parameters showed <br /> that the adsorption was spontaneous (except for chlorogenic acid) and exothermic. Adsorption isotherms and thermodynamics gave useful information about phenolic acid – <br /> β-glucan interactions.
Highlights
Polyphenols are secondary plant metabolites that have shown numerous positive bioactivities[1,2,3,4]
The results showed the positive value of standard reaction entropy ΔS0, which supported a spontaneous process in the interaction of phenolic acids with β-glucan
This study showed that phenolic acids interacted with β-glucan in a complex process affected by the concentration of phenolic acids, chemical structure of phenolic acids or pH value and temperature of environment
Summary
Polyphenols are secondary plant metabolites that have shown numerous positive bioactivities[1,2,3,4]. More recent studies have shown that they can interact with macromolecules like proteins, carbohydrates, and lipids in the digestive tract, which can affect their bioactivities[5,6,7]. Interactions with other compounds in the digestive tract can affect polyphenol accessibility for absorption (bioaccessibility), the actual amount that is being absorbed (bioavailability), and their bioactivities[5]. Dietary fibers can interact with polyphenols, “carry” them to the lower parts of the digestive tract[8] and by doing so, possibly influence their bioactivities. That is why interactions between dietary fibers and polyphenols are in the focus of present studies. To obtain more information about polyphenol and dietary fiber interactions, the adsorption process between polyphenols and dietary fibers has to be studied. Adsorption is a process in which molecules from the solution (adsorbate) adsorb onto the
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