Adsorption of Tea Polyphenols using Microporous Starch: A Study of Kinetics, Equilibrium and Thermodynamics.

Xianchun Hu,Xianfeng Du

doi:10.3390/molecules24081449

Xianchun Hu, Xianfeng Du

Open Access

https://doi.org/10.3390/molecules24081449

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Abstract

Microporous starch (MPS) granules were formed by the partial hydrolysis of starch using α–amylase and glucoamylase. Due to its biodegradability and safety, MPS was employed to adsorb tea polyphenols (TPS) based on their microporous characteristics. The influences of solution pH, time, initial concentration and temperature on the adsorptive capacity were investigated. The adsorption kinetics data conformed to the pseudo second–order kinetics model, and the equilibrium adsorption data were well described by the Langmuir isotherm model. According to the fitting of the adsorption isotherm formula, the maximum adsorption capacity of TPS onto MPS at pH 6.7 and T = 293 K was approximately 63.1 mg/g. The thermodynamic parameters suggested that the adsorption of TPS onto MPS was spontaneous and exothermic. Fourier transform infrared (FT–IR) analysis and the thermodynamics data were consistent with a physical adsorption mechanism. In addition, MPS-loaded TPS had better stability during long-term storage at ambient temperature.

Highlights

Tea polyphenols (TPS) are one of the main active substances in tea leaves [1,2]
The adsorption behavior of tea polyphenols (TPS) onto Microporous starch (MPS) may differ due to pH values
Microporous starch (MPS) granules were prepared via the partial hydrolysis of starch using α–amylase and glucoamylase

Summary

Introduction

Tea polyphenols (TPS) are one of the main active substances in tea leaves [1,2]. Tea polyphenols possess aromatic rings with one or more hydroxyl groups [3], which have been shown to provide significant health benefits, including antioxidant activity, anticancer activity, reducing blood fat, and lowering blood sugar; TPS are widely applicable in cosmetics, clinical applications, drugs, and food [4,5,6,7].Microporous starch (MPS) is prepared by reacting various raw starches with starch hydrolytic enzymes (α–amylase and glucoamylase) at temperatures under the gelatinization point [8,9,10,11,12,13].Microporous starch granules have plentiful micro pores expanding inside (hilum) from outside (surface), which allow smaller molecules to enter the holes of the granules [14]. Tea polyphenols (TPS) are one of the main active substances in tea leaves [1,2]. Microporous starch has remarkable adsorption performance because of its large specific surface area. It can be used as an adsorbent in food, medicine, cosmetics, agriculture and other fields [15,16,17,18]. Some oxidized substances (such as vitamin E, β–carotene, lycopene, etc.) can be protected efficiently by the adsorption of microporous starch [18]

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