Comprehensive Extraction Of The Active Ingredient In Green Tea Defective Research

In this paper the extraction of caffeine and polyphonels from inferior green tea was studied, respectively utilizing supercritical CO₂ and Al³+ ion precipitation extraction method.It was investigated the effect of extraction parameters on caffeine extraction, such as temperature, pressure, the extracting time and CO₂ flow rate. And it was found that in extracting caffeine from tea using SC-CO₂, water could remove caffeine from tea matrix effectively and could swell tea volume so as to increase the mass transfer area and ameliorate the mass transfer condition. The caffeine extraction ratio attained was 80%, dynamically extracting caffeine from the water saturated tea for 4 hours, at 338K, 28MPa and a CO₂ flow rate of 0.08 kg/min, in which ethanol aqueous solution (80%, φB) was added as the entrainer, the amount of which was 2.8% of the CO₂ usage in weight. And after the extraction, the amount of caffeine remained in tea ≤0.8%.The caffeine mass transfer mathematic model was established based both of the fix-bed extraction model and the feature of caffeine extraction extent variation with the extracting time. The result showed that the calculations from the model agreed with the experiment data. And it was also showed that the resistance of caffeine diffusion from the tea matrix to the boundary layer was an order larger than that from the boundary layer to the supercritical fluid phase.Primarily separating caffeine from the extract, the results showed that, in water phase separation method, no nocuousness got into the product and the caffeine loss was less than in sublimation method. The purity of the obtained caffeine coarse product was 86.6%.In the paper, the Al³+ ion precipitation method was used to extract tea polyphenols from both the inferior green tea and of its decaffeination remains. It was investigated the effect of the pH value of the precipitation system, the precipitator usage and the liquid-liquid extraction times on the purity and yield of the tea polyphenols. Precipitating the tea polyphenols in the leachate of tea and its decaffeination remains at pHaround 5.2 and a precipitator usage of 2.2g Al/ lOOg tea, then dissolving the precipitate using dilute acid, and then extracting the dilute acid solution of tea polyphenols once with equal volume of ethyl acetate, the purity of obtained tea polyphenols product was 84.09% and 92.16% respectively, and the yield was 7.35% and 6.51% respectively.