Study On Enzymatic Modification And Related Properties Of Dietary Fiber Of Jujube Residue

In the process of jujube juice processing, jujube residue is produced, which accounts for morethan80%of raw materials and is rich in dietary fiber, as a potential source of dietary fiber. Theintake of dietary fiber is closely related to health. Dietary fiber with high function has gained moreand more attention. As a result, it becomes necessary to study on new sources of fiber andmanufacture fiber products with high functionality. Therefore, this paper considered recyclingbyproducts from jujube juice processing and modifing the jujube residue fiber to improve itsfunctionality and compared the difference of structure and physicochemistry of jujube residue fiberafter modification. Moreover, it researched on the correlation of particle size and the properties ofinsoluble fiber and related properties of soluble fiber, designing to provide theoretical guidance forapplication of jujube residue fiber in the food industry. The main research content was as follows:Firstly, the modification effects of cellulase and xylanase were researched treating the solublefiber yield and insoluble fiber yield as the index. The modification conditions were furtheroptimized by combining two enzymes to improve the purity and increase the proportion of solublefiber. Response surface methodology was used to obtain the optimal condition as follows: cellulaseconcentration0.29%, xylanase concentration0.21%, reaction time49min, reaction temperature50℃, solid-liquid ratio of1:10without pH adjustment. Under the condition, the final percent ofsoluble fiber (SDF) and insoluble fiber (IDF) could reach14.65%and45.72%from6.79%and37.52%respectively.Secondly, the differences of microstructural characteristics and physicochemistry afterenzymatic modification were analyzed by this experiment. The results showed that water holdingcapacity, water binding capacity, swelling, oil holding capacity improved to some extent, whichcould be reasonably explained by the variation of microstructure of modified jujube residue fiber. Inaddition, the contents of flavonoids and polyphenols were compared and it found they had goodretention, the contents of them in product were10.68mg/g and15.32mg/g respectively.Thirdly, the relevancy between particle size and properties of insoluble fiber of jujube residuewas studied, comparing the physicochemistry properties of insoluble fiber under different particlesizes, containing hydration properties(water holding capacity, water binding capacity and swelling),oil holding capacity, adsorption properties(adsorbability of cholesterol, Cd2+、Pb2+and glucose) andcation-exchange capacity. The results showed that as the grinding particle size was100~120mesh,the physicochemical properties of insoluble fiber of modified jujube residue had bettercomprehensive performance. Combining with the taste, the best particle size range was100~120mesh, which could be grinded to such particle size in its application.Finally, the solubility and viscosity of soluble fiber could significantly affect its application.Therefore, this paper stuied on the properties of soluble fiber of modified jujube residue further. Itshowed that the soluble fiber had good solubility, when the temperature was60℃, its solubilitycould reach more than95%, so it didn’t need high temperature in its application; its viscosity wassmall even high concentration and it didn’t gelating, considering adding in some drinks withoutaffecting the original viscosity; At high salt concentration, the viscosity of soluble fiber changedlittle as ion concentration of solution was increasing, considering applying to high salt food as fiber supplement to improving fiber content in food. In addition, DEAE-Sepharose CL-6B was used toisolate components of soluble fiber. Four different components were obtained, namely a kind ofneutral sugar, three kinds of acidic sugar. They were mostly oligosaccharides, molecular weightwere around10241,2374,1438and769respectively and the proportion of the part of769was verysmall, which indicated xylanase and cellulase presented endochitinase activity.