Study On Preparation And Hypolipidemic Function Of Tea Dietary Fiber

Tea dietary fiber（TDF）was prepared from tea residues and modified to get cellulose-modified tea dietary fiber（CTDF）by cellulose or micronized tea dietary fiber（MTDF）by ultrafine grinding.Morphological structure of the three tea dietary fiber was observed by scanning electron microscopy（SEM）and infrared spectrum（IR）,components,physical and chemical properties,antioxidant activity and lipid-lowering function of these three dietary fiber were studied.Main results were as follows:1.The alkaline protease was used to prepare tea dietary fiber by removing the protein tea residues.Orthogonal test showed that p H、temperature、time and enzyme dosage affected the enzymatic hydrolysis of alkaline protease,the optimum condition of the enzymatic hydrolysis was the temperature 70℃,time 1.5 h,p H 9,enzyme dosage8.00 mg/g.The time、enzyme dosage、temperature and p H affected enzymatic hydrolysis of cellulose and the optimum condition was the temperature 45℃,time 2 h,p H 5,enzyme dosage 14.00 mg/g.2.The result of IR analysis showed that the two types of modification did not change the basic structure of tea dietary fiber.SEM results showed that the TDF,CTDF has space grid structure,particles of MTDF become smaller and gathered.3.The three tea DF were composed of total phenol,flavonoids,total pectin,cellulose,hemicellulose and lignin,among which each component content differences were:total phenol:MTDF>CTDF>TDF;flavonoids,total pectin:CTDF>MTDF>TDF;cellulose,lignin:TDF>MTDF>CTDF;hemicellulose:MTDF>CTDF>TDF;after being modified by cellulose or ultrafine grinding,cellulose content reduced significantly,hemicellulose content increased significantly,there is no significant difference between lignin content.4.The physical and chemical properties of the three tea dietary fiber were studied.The results showed that the activation of cellulose did not significantly affect the swelling capacity（SWC）,the water holding capacity（WHC）and the water binding capacity（WBC）of TDF,but the activation of ultrafine grinding significantly decreased them.The activation of cellulose significantly increased the oil-,fat-,cholesterol-and bile salts-binding capacities of TDF,while the activation of ultrafine grinding significantly decreased the oil-and fat-binding capacities of TDF,and strongly increased the cholesterol-and bile salts-binding capacity.5.The three tea DF have good antioxidative capacities in vitro.The results showed that,the ability to scavenge DPPH:CTDF>MTDF>TDF,which IC₅₀ values were 0.83mg/m L,0.50 mg/m L and 0.53 mg/m L respectively;the ability to scavenge·OH:TDF>MTDF>CTDF,which IC₅₀ values were:3.42 mg/m L,11.32 mg/m L and 10.38mg/m L respectively;total antioxidant capacity:MTDF>CTDF>TDF.6.The results of animal test showed that the three kinds of dietary fibers could significantly decrease total cholesterol（TC）,total triglycerides（TG）,and Low-density lipoprotein（LDL-C）in serum and hepatic,significantly increased HDL-C/TC in serum and hepatic,and the effect of CTDF and MTDF was better than that of TDF.Histopathological analysis of livers showed that MC mice fed a high cholesterol diet had hepatic parenchymal cells filled with macrovesicular fat（macrovesicular steatosis）,and the intercellular boundaries in them were not clear,while the three tea DF significantly improved the effect.The results also showed that the three tea dietary fiber significantly promoted the excretion of feces and fecal lipids and significantly improved the activities of superoxide dismutase（SOD）and glutathione peroxidase（GSH-Px）in serum and liver and decreased malondialdehyde（MDA）in serum and hepatic.It was concluded that the three tea dietary fiber could improve lipid profiles of serum and hepatic mice fed a high cholesterol diet and the mechanism of the action might be due to the promotion of fecal excretion of lipids and the antioxidant activity.