Obtaining caffeine through waste tea fiber and stalks by making of the supercritical carbon dioxide extraction method

Caffeine (C8H10O2N4) is an alkaloid which is formed through its basic structure, purine. The ingredients are tea, coffee, cola, nut, mate ( Paraguay tea) and cacao on a limited scale. Caffeine is mostly used in drinks with cola and commonly utilized in the medicine industry for its activating and muscle relaxant effect.Caffeine is obtained by two methods; through synthetic methods or through extraction of some plants like tea and coffee. In the dry element of tea, there is 3-4% caffeine in the mass and approximately 1% in the tea stalks. In this experimental study, the wastes of tea fibers and stalks, which do not have any economic value, are used. By making use of the supercricitical carbon dioxide extraction method, caffeine is extracted from the tea wastes and quantitative analysis is realized through HPLC.At the end of the experimental studies, the optimum conditions that provide maximum caffeine production are determined as extraction period 420 minutes, flow rate of carbon dioxide 11 g/ min, temperature 60°C, pressure 250 bar, mean particle size 0,202 mm. In these optimum conditions which are detected through experiments, caffeine is obtained from the tea leaves in the proportion of 15,20 mg caffeine/g dry waste tea. Ethanol is added in order to analyse the effect of the co-solvent and the optimum conditions are identified as ethanol/CO2 ratio 5,23 g ethanol/100 g CO2, extraction period 180 minutes, temperature 65 °C, pressure 250 bar, mean particle size 0,202 mm and in these conditions caffeine is obtained in the proportion of 14,95 mg caffeine/g dry waste tea. It is observed that more caffeine can be extracted in a shorter period with the addition of ethanol. Additionally a mathematical model has been developed concerning the mass transfer coefficiency. At the results of the experiments which are realized under fixed circumstances as; pressure 250 bar, mean particle size 0,202 mm, CO2 flow rate 10 g/min, mass transfer coefficiency for 60°C is calculated as kL=2,078.10-8 m/min; and on repeating the extraction at the same fixed conditions with %5 ethanol and %95 CO2 by weight, it is calculated as kL=3,724.10-8 m/min. Consequently it has been observed that mass transfer coefficiency is increases approximately 1.8 times when ethanol is utilized.