Abstract:In order to improve the solubility of Kangpu tea cellulose, soluble dietary fiber ( SDF ) was prepared from Kangpu tea cellulose by enzymatic hydrolysis of cellulase and xylanase. The process parameters were optimized by single factor experiment and Box-Behnken response surface method, and the physical and chemical properties and structural characteristics of the samples before and after enzymatic hydrolysis were determined. The results showed that the optimal preparation conditions were as follows : the mass ratio of cellulase to xylanase was 4 : 1, the amount of composite enzyme was 2.5 %, the enzymatic hydrolysis time was 2.6 h, the enzymatic hydrolysis temperature was 50 °C, and the pH was 5.0. Under these conditions, the SDF preparation rate was 13.4 %. After enzymatic modification, the expansion of SDF increased the most, about 280.8 %. The increase of water holding capacity and cholesterol adsorption were 146.0 % and 160.9 %, respectively. The increase of oil holding capacity and bile salt adsorption was 115.2 % and 76.1 %, indicating that compound enzyme modification could significantly optimize the functional properties of dietary fiber. Scanning electron microscopy, infrared spectroscopy and thermogravimetric analysis showed that enzymatic hydrolysis destroyed the tight structure and hydrogen bond network of cellulose, reduced crystallinity and thermal stability, and gave the fiber better solubility and functional activity. This study explored the preparation process of soluble dietary fiber in Kangpu tea by-products, and provided a process reference for the development of new food ingredients.