Adsorption of (−)-epigallocatechin-3-gallate (EGCG) onto oat β-glucan

Polyphenol–polysaccharide interaction attracted much attention due to its crucial impact on the functional and sensory quality of foods. Monomers of tea polyphenols (TP) were selectively adsorbed by oat β-glucan and (−)-epigallocatechin gallate (EGCG) was the mostly adsorbed one in terms of adsorption capacity (qe) and efficiency (Ee) determined by equilibrium dialysis. Contrast to Langmuir, Freundlich and Redlich-Peterson models, Toth model fit best to the adsorption isotherm of EGCG. The adsorbing variables were optimised using response surface methodology. Linear variables of pH and temperature (T), interactive terms of EGCG concentration (CEGCG)/buffer concentration (CPBS) and pH/T and all quadratic variables of C EGCG 2 , pH2, C PBS 2 and T2 made significant senses on qe. The highest qe could be achieved with the following conditions: CEGCG 0.7 mg/mL, pH 5.80, CPBS 0.10 M and T 50 °C. The consistency of the experimental (321.5 μg/mg) and predicted (333.3 μg/mg) values in qe confirmed the adequacy of the response surface equations. The bonds which governed the interaction between EGCG and oat β-glucan was hydrogen bond.