Study On Preparation Of High-quality Wheat Bran Dietary Fiber And Their Monosaccharide Compositions And Properties

Subject to the wheat bran as raw material,process conditions of preparation of high-quality dietary fiber by different methods were studied,and the monosaccharide compositions and properties of different dietary fiber samples were measured and analyzed.The optimal experimental conditions for high-quality dietary fiber from wheat bran by cellulase were the ratio of wheat bran to water 1:10,cellulase addition 20U/g,pH 5.0,temperature 40℃and action time 4h,while water-soluble dietary fiber was 12.47%,water-insoluble dietary fiber was 38.15%,and the rates of them was 1:3.06.For preparation of high-quality wheat bran dietary fiber by xylanase,the optimum conditions were as follows:hydrolysis temperature 70℃,hydrolysis time 2h,xylanase addition 15U/g,ratio of material to water 1:15,while the ratio of SDF to IDF was 12.53:38.41≈1:3.07.For preparation of high-quality wheat bran dietary fiber by Extrusion method, the most suitable experimental parameters were material moisture content 11.6%, extrusion temperature 80℃,screw speed l00r/min,screw length into three sections,while the ratio of SDF to IDF was 12.47:38.51≈1:3.09.Using high-performance liquid chromatography for the analysis of monosaccharide compositions,the results showed that the original wheat bran sample,and dietary fiber samples prepared by cellulase and extrusion method were 77%-80%composed of cellulose,arabinoxylan of hemicellulose,and glucuronic acid of xylan,as well as 11%-15%polygalactose and 6%-10%fructan;the components of the dietary fiber sample prepared by xylanase were 85.22% arabinoxylan and glucuronic acid of xylan mainly,and 9.84%polygalactose and 3.83%fructan. Water holding capacity,oil absorption capacity,swelling capacity,soluble matter content,cation exchange capacity,nitrite adsorption capacity,cholesterol absorption capacity,viscosity and particle size distribution of different dietary fiber samples were analyzed.The results showed that water holding capacity of the samples prepared by extrusion processing,cellulose and xylanase method increased 136%,132%and 126%than the original samples of wheat bran,respectively;the corresponding oil absorption capacity and swelling capacity increased 238%, 231%,213%and 28.9%,24.7%和18.7%;the swelling capacity decreased firstly and then increased;with the increase of temperature,soluble matter content increased, and soluble matter contents of four samples were almost the same at the same temperature;cation exchange capacity of dietary fiber samples prepared by Enzymatic method was poor,and extrusion processing had not obvious effect on the cation exchange capacity of dietary fiber;cation exchange capacity was stronger at pH 2;cholesterol absorption capacity at pH7 of the samples prepared by xylanase, cellulose method and extrusion processing were 7.82mg/g,7.48mg/g,7.39mg/g, respectively,while the original sample's was 4.96mg/g;cholesterol absorption capacity was stronger in the neutral conditions(pH of simulated intestinal environment)than in the acidic conditions(simulated stomach acidic conditions); the viscosity of sample solution increased as the concentration increased gradually, but the increasing trend was ease;the viscosity of extrusion processed was bigger, and the viscosity of the original sample was smaller,13.9mPas and 12.5mPa-·s, respectively;73%-75%of the particle sizes of the dietary fiber samples prepared by Enzymatic method and extrusion processing were distributed in the＜160 range,and almost 70%of the original sample particle size was distributed in the＞180 range.SEM(Scanning Electronic Microscope) observation results showed that the original dietary fiber sample had large particles and smooth surface,and the structure was very dense;dietary fiber sample prepared by cellulase had granular surface,and there were some smaller pores,however,the structure was still relatively close;dietary fiber sample prepared by xylanase was indirectly space layered network structure,and network structure had no rules;the structure of dietary fiber sample prepared by extrusion were destroyed more seriously,and it had different shapes,flake as well as small particles,having loose structure and a larger number of pores.