Back-extraction Of High-purity Tannins And Reduction Of Gallic Acid Residues

Tannic acid is a kind of natural plant gallnut as raw material,through physical and chemical extraction and purification process products.Tannic acid is a polyphenol compound,has unique chemical properties and special physiological and pharmacological functions,has been widely used in food,medicine,metallurgy,mineral processing,leather and other industries,the market demand is very big.However,at present,the purity of gallic acid is generally between 90%~95%,the gallic acid residue is generally between 2%~4%.Therefore,it is of great significance to study the extraction of high purity tannic acid from galla chinensis and purification of gallic acid and the residue of gallic acid.In this paper,the optimization of the extraction process of gallic acid and purification of gallic acid and reverse extraction of gallic acid were studied:1)Using ethyl acetate as the extraction agent,extraction method combined with extraction using organic solvent extraction and ultrasonic assisted extraction of tannic acid in Galla chinensis,the extraction temperature and extraction time,solid-liquid ratio of gallnut powder with ethyl acetate and other factors were studied on extraction efficiency.On the basis of single factor tests,the process response surface optimized for extraction of tannic acid: gallnut extraction temperature was 30 ?,extraction time was 5h,gallnut powder and ethyl acetate solid-liquid ratio was 1:5(g:mL).Under this condition,Chinese gall tannic acid content can be achieved 95%.2)According to the different solubility of tannic acid in organic solvent and aqueous phase,the influencing factors of tannic acid and ethyl acetate extraction of tannic acid and solid-liquid ratio,solid-liquid ratio,different extraction solvent were studied on the purification effect of the.On the basis of single factor tests,it was got the method of preparation and purification of tannic acid,through the orthogonal test,the optimized purification process of tannic acid,tannic acid and ethyl acetate was 1:5(g:mL),the ratio of solid to liquid liquid extraction of tannic acid and liquid ratio of1:2.5(g:mL),pH 6.8 sodium phosphate solution was selected as stripping agent.Under this condition,Chinese gall tannic acid content can be achieved 98.5%.3)The extraction method of reverse extraction was usded to reduce the amount of application of high purity tannic acid gallic acid residue in the production,through the test on the factors the solid-liquid ratio of ethyl acetate,the solid-liquid ratio of tannic acid and extraction of tannic acid and,different extraction agent,it was obtained the best condition factors.On the basis of single factor tests,the optimum conditions to reduce the anti extraction residue of gallic acid of high purity tannic acid:the liquid ratio of tannic acid and ethyl acetate was 1:5(g:mL),the liquid ratio of tannic acid and extraction liquid was 1:2.5(g:mL),pH 6.8 sodium phosphate solution was selected as stripping agent.Under these conditions,the gallic acid content in gallic acid could be reduced to less than 1%.