Preparation And Modification Research Of Tea Polyphenols

Tea is a national drink of China. China is the first country founding tea'plant, collecting tealeaves, preparation tea and drinking tea. In China, there are more than 5000 yeas that people use tea. Tea is not only a necessary but also a medicine for Chinese.With the developing of science technology, extraction and use of active compositions in natural substances have progressed than before. Since H.Roberts had studied tea polyphenols(TP), many functions of TP had been found gradually. It was noted by research that TP is a natural nontoxic antioxidant and a ideal medicine, which has the bioactivity of clearing free groups and anti-oxidation and good virtues of inhibiting bacterium, virtues, cancer, tumors and prevention and cure heart disease.TP production was mainly been used as medicine, cosmetic, antioxidant, cleanse, and drink, and so on. There were 3 preparation methods of TP, which were dissolvent method, deposition method and adsorption method.TP need to be modified for their bad liposoluble ability and low bioavailability. At the present time, there were 3 modification methods of TP, which were emulsification method, dissolution method andmolecular modification method.China is a main country of producing tea. The average tea output yearly was about 600, 000 tons in China, but there were around 100, 000 tons of middling and low-end tea that were kept long in stock and 16, 000 tons byproducts of tea annually. These middling and low-end tea and byproducts of tea had been burdens of tea factories because of their low worth and disposal, but they can be used as raw materials of TP production.Nowadays, factories in China mainly prepared TP by means of dissolvent method, which had the shortcomings of long preparation time, high operation temperature, low content, activity of products, insecurity in preparation and toxic remain in product due to using chloroform during preparing TP. As a result, TP product was sold difficultly and was kept long in stocks largely. So, new preparation technology of TP was studied and developed in order to increase predominance of Chinese TP in civil and international markets.Liposoluble TP was mainly prepared by acidation in China, but the activity of Liposoluble TP was lowed remarkably due to the reduction of hydroxyl during TP preparation. Therefore, research of new TP modification method had important practical meaning and science values.Based on these problems of TP preparation and modification, solid-liquid extraction of TP, purification of TP, molecular modification of TP and molecular envelopment of TP were studied in this paper.It was noted in solid-liquid extraction of TP that TP stability in water lowed with the increasing of temperature, nitrogen could slow and reduce efficiently oxygen in air solving in water and contacting with TP so as to low oxidation rate of TP and increase the stability of TP in water; The best conditions of nitrogen protection-ultrasonicextraction TP were 8 times the amount of water to the tealeaves, 50 ℃ and 30min for 3 times, and the extraction rate was 25.64%.The results of TP purification showed that 4# adsorptive resin had better selective adsorption to TP and caffeine due to hydrogen bond, the adsorptive capacity of 4# resin to TP and caffeine were 66.27mg/g and1. 34mg/g respectively, and elution rate of 4# resin to TP and caffeine were 95.54% and 95.85% accordingly; the adsorptive capacity of 4# resin to TP was the most under 20℃ temperature, and Langmuir equation was q/71. 42=6. 86C/(1+1. 86C); the best adsorption and elution conditions of 4# resin were 1.4mL/min of flow rate and pH3.0 when adsorption and2.0mL/min of flow rate and 80% ethanol when elution; the practical adsorptive capacity of 4# resin to TP was 53. 15mg/g, and the TP product content was more than 95% in which caffeine was less than 1% and the production rate was 18. 56% only by 1 time adsorption and 1 time elution.The tests of TP modification noted that the method of protecting hydroxyls before modifying TP molecules was feasible; there were hydroxyls and adjacent hydroxyls and not aromatic ketenes and quinone in CTP; hydroxyls and adjacent hydroxyls content of CTP were 19. 79% and 14. 48%, hydroxyls and adjacent hydroxyls content of TP were 30. 42% and 24. 15%, and the ratios of hydroxyls to adjacent hydroxyls of CTP and TP were 73.64% and 79.39% respectively; long chains were introduced into CTP molecules and the main body structure of CTP was similar to TP molecules; CTP added directly were good soluble in plant oils and had better oxidation results, and the best addition quantity was 200mg/kg.It was showed by TP liposome preparations that re- emulsification and disperse method was the best methods of common TP liposome, the entrapment of TP was more than 75% and the average diameter of TP liposome was 0.941μn; by freezing and thaw treating, the entrapment of TP increased to 88. 89% and the stability was enhanced, but the diameter ofTP liposome increased also, so antifreeze were added in order to inhibit diameter expanding and glycerin was the most effective; the result was the best by using 3g/L PVA preparation TP long circle liposome, the enwrapping rate of PVA was 34. 22%, the entrapment rate of TP was 88. 64%, the stability of TP long circle liposome was better than TP common liposome.