Tea decaffeination

The decaffeination of tea is currently practised both using the organic solvents methylene chloride and ethyl acetate and using supercritical carbon dioxide [19]. The latter process is discussed in section 5.4.5. The import into the USA of tea decaffeinated by the methylene chloride process is currently prohibited though this solvent may be used within that country [18]. 

In recent years there has been growing disquiet among consumers about the use of synthetic chemical solvents in the food industry. This has led to the development of processes utilising innocuous solvents of natural origin. Water is a very good solvent for caffeine but has a very low selectivity. It also dissolves the many other water-soluble compounds present in green coffee 

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Huang MT, Xie JG, Wang ZY, Ho CT, Lou YR, Wang CX, Hard GC and Conney AH. 1997. Effects of tea, decaffeinated tea, and caffeine on UVB light-induced complete carcinogenesis in SKH-1 mice demonstration of caffeine as a biologically important constituent of tea. Cancer Res 57(13) 2623-2629. 

Wang ZY, Huang M, Lou Y, Xie J, Reuhl K, Newmark H, Ho C, Yang C and Conney A. 1994. Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[<3]anthracene-initiated SKH-1 mice. Cancer Res 54(13) 3428-3435. 

Supercritical carbon dioxide has been industrially used in a variety of processes, including coffee decaffeination, tea decaffeination, and extraction of fatty acids from spent barley, pyrethrum, hops, spices, flavors, fragrances, com oil, and color from red peppers. Other applications include polymerization, polymer fractionation, particle formation for pharmaceutical and military use, textile dyeing, and cleaning of machine and electronic parts. 

This patent on a three step tea decaffeination process is included in chronological order with the coffee patents because of its similarity to U.S. 3,843,824 which describes a three-step process for the decalfeination of roasted coffee. In the first step, tea aromas are removed from dry tea using dry supercritical CO2. In a next step, the tea is moistened and moist CO2 is passed through the tea to extract the catfeine. In a third step the aromas are returned to the moist tea in the following manner. The aromas are dissolved into a sU eam of supercritical CO2 which is then passed first through a heat exchanger to liquify the CO2 and then to the vessel containing the tea which is now dried. When the tea vessel is filled with the solution of liquid CO2 and the aromas vapor CO2 is withdrawn from the vessel and the aromas precipitate into (and onto) the tea. 

Takahashi, T., 320, 330, 331 Tea decaffeination plant, 7 Temperature-entropy diagram, 138 Temperature rising elution fractionation (TREF), 197, 202-203 Ternary mixtures, phase diagrams, 71-84 Testosterone, 340 Tetracyclic steroids, 293 Thermodynamic modeling, 99-134 Thies, M. C., 88-90... 

Products and Uses Found in coffee (decaffeinated), fruits, tea (decaffeinated), and vegetables as a coloring agent, flavoring agent, solvent, synthetic flavoring substance, and additive. 

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