Optimization of adsorption conditions of tea polyphenols by modified citrus peel dietary fiber and its in vitro simulated digestion stability

【Objective】 The optimization of adsorption condition of tea polyphenols by modified citrus peel dietary fiber and the stability of its complex in a simulated digestive environment was explored with the aim of providing technical support for the application of tea polyphenols in healthy food.【Method】 Citrus peel dietary fiber modified using dynamic high pressure microfluidization（DHPM）was adopted to adsorb tea polyphenols to investigate the effects of temperature，time，tea polyphenol concentration and pH on the adsorption capacity.Response surface methodology was applied to optimize the adsorption conditions and a simulated gastrointestinal digestion model was established to investigate the digestive stability of dietary fiber-tea polyphenol complex.【Result】 The adsorption of tea polyphenols by modified citrus peel dietary fiber was negatively correlated with temperature and the amount of tea polyphenols adsorbed rapidly tended towards reach equilibrium over 60 min and was maximal at pH 7.0.Moreover，tea polyphenols adsorbed reached saturation when the concentration of tea polyphenols was increased to 3.0 mg/mL.The results of the response surface tests revealed that temperature had the greatest effect on the adsorption of tea polyphenols，followed by time，tea polyphenol concentration and pH，and the interactions of temperature and time，and temperature and tea polyphenol concentration exhibited significant effects on the adsorption of tea polyphenols（P<0.05，the same below）.The adsorption condition of tea polyphenols by modified citrus peel dietary fiber were optimized at a temperature of 5℃，a time of 61 min，tea polyphenol concentration of 3.9 mg/mL and a pH of 7.0.Under these conditions，the adsorption amount of tea polyphenols by modified citrus peel dietary fiber was 54.26 mg/g，which was close to the model theoretical value（54.46 mg/g）.The in vitro gastric and intestinal digestion tests demonstrated that the modified citrus peel dietary fiber-tea polyphenol complex possessed a tea polyphenol retention rate of 92.07% and 69.73%，respectively which were significantly higher than those of pure tea polyphenols（84.17% and 47.29%）.【Conclusion】As modified citrus peel dietary fiber can form a complex by adsorption and binding to improve the stability of tea polyphenols in the gastrointestinal digestion environment，it can be used as a natural protective carrier of tea polyphenols.