Preparation Of Dietary Fiber From Gracilaria Lemaneiformis And Its Application In Yogurt

Dietary fiber was considered as the seventh nutrient because it had varies ofimportant physiology functions. These functions include regulating levels of the bloodsugar and the blood lipid, preventing cancer and so on. Dietary fiber has become afocus because of its special properties and physiology function. There is plentydietary fiber in Gracilaria lemaneiformis, which makes it a good material for dietaryfiber preparation.In this study, fermentation and enzymolysis were used to prepare dietary fiberfrom Gracilaria lemaneiformis, and the effect of processing methods to the physicalproperty of dietary fiber were discussed. Finally, processing technology of dietaryfiber yogurt was studied. The major results of this paper are as follows:1. Preparation of dietary fiber from Gracilaria lemaneiformis（1）Gracilaria lemaneiformis was fermented to prepare dietary fiber, and theoptimal process of preparation was investigated. A mixed strain of Trichoderma virideand Aspergillus oryzae was chosed for fermentation. Regard yield as parameter, theoptimal process of preparation was investigated by orthogonal array design. Results:the ratio of solid to liquid was1:5, the fermentation temperature was28℃, thefermentation pH was6.0, the fermentation time was7d, and the ratio of Trichodermaviride to Aspergillus oryzae was1∶1. The yield of the dietary fiber fromGracilarialemaneiformis was71.36%, the expansibility of the dietary fiber was14.5mL/g whenthe water holding capacity was6.23g/g.（2）The hydrolysis of Gracilaria lemaneiformis by trypsin and cellulase wasstudied separately. The first step: The trypsin was choosed by screening, and regarddegree of hydrolysis as parameter, the optimal enzymatic hydrolysis conditions oftrypsin were obtained. Results: the mass fraction of trypsin was2.5%, enzymolysispH was7.5, the enzymolysis temperature was55℃, and the enzymolysis time was4h.The second step: The sample hydrolyzed by trypsin was enzymolysis by cellulase to prepare soluble dietary fiber. Regard yield of soluble dietary fiber as parameter, theoptimal condition of cellulase were obtained by orthogonal array design. Results: themass fraction of cellulase was0.75%, enzymolysis pH was4.5, enzymolysistemperature was60℃, and the enzymolysis time was3h. The yield of soluble dietaryfiber was13.30%, while the dietary fiber was68.36%.（3）In order to make the dietary fiber with good sense organ character, thispaper discusses the bleaching processes of dietary fiber. Results: the amount of bleachsolution was30times as much as the raw material, the mass fraction of NaClO was0.5%, pH was4.0, and the bleaching time was40min.2. The physiological activity of dietary fiber prepared from Gracilarialemaneiformis（1）The result of absorption: The dietary fiber prepared from Gracilarialemaneiformis could absorb fat, and the processing methods could affect theadsorption. On adsorption of fat, dietary fiber prepared by fermentation was the best,and the dietary fiber prepared by enzymolysis was better than the one prepared bychemical method. The adsorption of saturated fat was stronger than that ofunsaturated fat. The dietary fiber prepared from Gracilaria lemaneiformis couldabsorb cholesterol, and the adsorption could be affected by processing methods andenvironmental system. On adsorption of cholesterol, dietary fiber prepared byfermentation was the best, and the dietary fiber prepared by enzymolysis was betterthan the one prepared by chemical method. The adsorption in neutral condition wasstronger than in the acid condition.（2）The result of animal experiments: The dietary fiber prepared fromGracilaria lemaneiformis could significantly reduce the contents of TC, TG andLDL-C, and increase the content of HDL-C in serum. The dietary fiber could promotethe output of FC and FBA. Therefore, the dietary fiber has the potential to regulatelipid metabolism. The processing methods could affect the physiological activity ofDF. On regulating lipid metabolism, dietary fiber prepared by fermentation was thebest, and the dietary fiber prepared by enzymolysis was better than the one preparedby chemical method. 3. The application of dietary fiber prepared from Gracilaria lemaneiformis inyogurtThe dietary fiber prepared from Gracilaria lemaneiformis was mixed withreconstituted milk, and fermented by lactobacillus.The production technology of DFyogurt was optimized by response methodology, taking DF addition, bacterialload,fermentation time as independent variables and sensory evaluation score of DF yogurtas dependent variable. The optimal fermentation technology was obtained as follows:DF addition was0.93%, bacterialload was7mL, and fermentation time was5.3h. Theproduction was homogeneous and smooth with appropriate sweetness and sourness.