Tea-leaf Protein And Drosspolypeptide Preparation And Properties Ofa Preliminarystudy

Tea residues are a by-products of tea after extracting tea polyphenols and other functional active material, which contain 20%~30% of protein and suitable amino acid composition. Tea residues protein, a kind of plant protein resources, has not yet been fully developed and utilized. Because that it contains 80% glutelin and 14% prolamine and is difficult to directly extract with water. Moreover, it is difficult to directly digest and absorb by the body due to its bad functional properties. At present, the application study of tea residues protein was still in the stage of laboratory and it was mostly extracted by a method of chemical alkali distillation. And there is few reports about enzymatic extraction with a low yield. In this paper, we use tea residues as raw material and the main purpose are as follows: optimize process parameters of alkali extraction, improve the yield of alkali extraction, analyze the physical and chemical properties of tea residues protein from alkali extraction; separate and purify the tea residues protein from alkali extraction and make a study on the purified protein about the antioxidant activity in vitro; use tea residues protein to prepare tea residues peptides, optimize the process conditions of the preparation and investigate its antioxidant activity in vitro.First of all, the alkali extraction process of tea residues protein is optimized.The optimum technology of protein extraction is: the Na OH concentration 0.1mol/L, the extraction temperature 60 °C, the extraction time 2.5 h and the ratio of material to liquid 1:50.Secondly, the extracting solution was disposed by isoelectric precipitation,hydrogen peroxide bleaching, dialysis, and drying to get the preparatory purified protein samples. The molecular weight distribution, amino acid composition, nutritional value, functional properties and in vitro antioxidant activity were analyzed. The results indicated that the weight-average molecular weight of tea residues crude proteins(Se-TP) from alkali extraction were861073 Da, 233645 Da, 36595 Da and 2696.82 Da, respectively. The amino acid composition of tea residues crude protein was rich, which contained 7 kinds of essential amino acid and the contents of glutamic acid, aspartic acid and leucine are higher with the percentage of 13.78%, 11.41% and 10.42%,Shanghai Normal University Master of Philosophy Abstract respectively. In addition, tea residues crude protein has a preferable effect similar to the antioxidants of Vc on the scavenging rates of DPPH free radical and hydroxyl free radical.Thirdly, tea residues crude protein was purified and four components(Se-TP0, Se-TP1, Se-TP2 and Se-TP3) were obtained. The distribution of molecular weight showed that Se-TP2 and Se-TP3 were relatively uniform,while Se-TP0 and Se-TP1 were protein complexes composed of multiple peaks.Antioxidant experiment in vitro showed that tea residues purified protein had certain remove effect on DPPH free radical and hydroxyl free radicals.At last, the digestion process conditions of tea residues crude protein was optimized. The results showed that the optimum technology condition was as follows: temperature 60 °C, p H 8.5, reaction time 3 h and the amount of enzyme 2‰. Under this optimal conditions, the maximum digestion rate was98%. In addition, tea residues polypeptide also had certain scavenging effect on DPPH free radical and hydroxyl free radicals.