The Extraction Of Natural Antioxidant Polyphenols In Food Preservation

The thesis focused on extraction, analysis and application of tea polyphenols(TP)as follows:Systemic study on the extraction of tea polyphenols was carried out. Firstly, the influence caused by some factors on TP leaching rate was studied. The orthogonal experiment showed that the optimum condition of leaching TP was- 60% ethanol as solvent, under 70℃, the ratio of tea and solvent is 1:20, leaching 2 times and 20minevery time. Under the conditions ,the maximum leaching rate of TP reached the 22.5% of tea. The influence of experiment equipment and filter process on TP leaching rate was studied. The result showed that filtering when solution was hot and using the equipment with condensator and N2 could benefit enhancing the rate of TP leaching. Secondly, the condition of extracting TP by depositing TP with metal ion was studied. Through repetitious experiment, the optimum condition of precipitation method was Al3++ Zn2+ as precipitator ,dissolving precipitation with HC1. With this conditions ,the yield and purity of TP was improved to 11.8% and 99.5%.Infrared spectra showed absorption as following:benzene absorption at 1610cm-1, 1510 cm-1 , pyrones absorption at 1200 cm-1, 1020 cm-1 and 820 cm-1, and phenol hydroxy absorption at about 3400 cm-1. Compared with the standard spectra of catechin EC ,it could be certified that its frame included 2-phenyl-benpyrones. On the basis of previous work, TP was analyzed by HPLC. Compared with standard samples , EGCG, EC and +C were inspected out in TP sample and we quantitatively determined the content of EGCG, EC and +C in TP sample.TP was used as natural food antioxidant to preserve chilled pork, and the effect was appraised by determining the sensory quality, microbial and physichemical value under 4±0.5℃. The results showed that 0.03%TP could lower the value of total quantity of bacillus, total volatile basic nitrogen(TVB-N) .peroxide value (POV) and prolonged the shelf-life of pork when compared with no addition sample , but also could discolor pork. It was remarkably and significantly discovered that 0.01% tea polyphenols, 0.01%VE and 0.01%VC added to chilled pork could not only reduce value of total quantity of bacillus, TVB-N and POV, but also could restrain discolour.