Adsorption of procyanidins B1 and B2 onto β-Glucan: adsorption isotherms and thermodynamics

The interactions between phenolic compounds and dietary fibers have generally received considerable attention because these interactions have a variety of applications, for example, in the production of functional foods, in the pharmaceutical industry, or in the production of films used as packaging materials for food. The aim of this study was to investigate the interactions between two flavan-3-ols: procyanidin B1 and procyanidin B2, and dietary fiber β-glucan. The adsorption process was studied at different temperatures (25, 37 and 45 °C) and different pH values (1.5, 5.5 and 10.0). The adsorption capacity of β-glucan for procyanidins (q_e) ranged from 44-489 mg g^-1, depending on temperature and pH, and was generally higher for procyanidin B2. At the temperatures tested, the lowest q_e values for both procyanidins were obtained at 37 °C, while at the pH values used, the lowest q_e values were obtained at pH 5.5. The experimental data were fitted by Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, and Hill isotherms. Analysis of the fit of the applied isotherms led to the conclusion that the adsorption process studied was physical in nature in the range of applied temperatures and pH values. The process was spontaneous and exothermic for both procyanidins.