Study On Preparation And Physicochemical Characteristics Of Tea Dietary Fiber

Tea dietary fibers （DF） were extracted from tea residue respectively throughchemical and enzyme extraction method. The preparation technology, component andphysicochemical characteristics of soluble dietary fiber （SDF） and insoluble dietary fiber（IDF） of tea were studied. The aim of this study was to provide a new thought for thecomprehensive utilization of tea and a theoretical basis for the application of tea dietaryfiber in food industry. Main results are as follows:1. Tea dietary fiber extracted by chemical method: on the base of single-factor test,the preparation technology of tea dietary fibers was studied respectively through quadraticregression of orthogonal rotation test and the method four factors three levers oforthogonal design test （L₉3⁴）. The results showed that the optimum technologicalparameters of SDF was temperature 79℃, solid-liquid ratio 1:35, time 2.2 h, hydrochloricacid concentrate 1.5 mol/L and the extraction rate was 49.72% on the optimum condition.The optimum technological parameters of IDF was temperature 55℃, solid-liquid ratio1:15, time 0.5 h, sodium hydroxide concentrate 0.5 mol/L and the extraction rate was69.89%.2. Tea dietary fiber extracted by enzyme method: on the base of single-factor test, thepreparation technology of tea dietary fibers was studied through five factors four levers oforthogonal design test (L₁₆4⁵). The results showed that the optimum technologicalparameters of SDF was temperature 60℃, enzyme added 0.08g/g, pH 9.0, time 2.0 h,solid-liquid ratio 1:20 and the extraction rate was 53.72% on the optimum condition. Theoptimum technological parameters of IDF was temperature 65℃, enzyme added 0.004g/g,pH 4.0, time 2.0 h, solid-liquid ratio 1:10 and the extraction rate was 94.12%.3. Physicochemical characteristics of tea dietary fiber: tea dietary fiber had goodphysicochemical characteristics. SDF had good water solubility. IDF could adsorb NO₂^-and metal ions such as Fe²⁺、Mg²⁺、Cu²⁺、Pb²⁺、Hg²⁺. The swelling capacity （SWC）, thewater holding capacity （WHC）, the water binding capacity （WBC）, cation exchangecapacity （CEC） of IDF were better than that of SDF, but the deposition density and theadsorption capacity of fat, cholesterol and sodium cholate of SDF were better than IDF.Physicochemical characteristics of tea dietary fiber extracted by enzyme method werebetter than that by chemical method.4. The effect of different factors on physicochemical characteristics of tea dietaryfiber was studied. The water solubility of SDF by two kinds of extraction method improved with the increase of temperature, and tended to rise first and then fall with theincrease of pH. The change of temperature and pH had no significantly effect on WHC ofIDF extracted by chemical method, but salt solution significantly decreased WHC of thetwo IDF. The adsorption capacity of the two IDF to NO2" increased with the increase oftemperature and time, but decreased with the increase of pH. The time and pH hadsignificant effects on the adsorption capacity to metal ions of the two IDF. At pH of 7.0,the adsorption rate to Cu²⁺ were 86.15%、85.37% respectively, the adsorption rate to Pb²⁺were 87.39%、81.72%, the adsorption rate to Hg²⁺ were 93.79%、90.30%. In general,physicochemical characteristics of tea dietary fiber extracted by enzyme method werebetter than that extracted by chemical method.