The three most widely used methods used to decaffeinate tea (and coffee) are carbon dioxide, water, and ethyl acetate. Ethyl Acetate (Tea and Coffee)
The leaves/beans are soaked with the ethyl acetate solvent, which bonds with the caffeine molecules. When the solvent and water are evaporated, the caffeine is strained out and dissolves in the ethyl acetate. The ethyl acetate-caffeine solution is then drained away, and residual amounts of ethyl acetate are removed by heating and evaporation. In this process, large amount of the health-promoting flavonoids and antioxidants are also washed away, and some of the solvent residue remains. This is the least expensive process.
Water Processing (Tea & Coffee --different techniques)
Tea: With this method, leaves are placed into hot water, under very high pressure. In the water, the caffeine and flavor components are dissolved. After the water has become saturated, the caffeine is removed by passing the water through carbon filters. The first batch of leaves are then discarded, and a new batch is placed into the water. The caffeine in the second batch dissolves into the water, but the flavor is retained. Because antioxidants are also water soluble, the level of antioxidants is likely impacted in water extraction.
Coffee: In single-stage water processes the beans are soaked as a single batch with plain water, extracting both the caffeine and the flavor. This weak extract is then filtered through activated charcoal to remove the caffeine. The filtered flavor-charged water is then partially dried to concentrate the weak extract and sprayed onto the decaffeinated beans to restore flavor back to them.
Carbon Dioxide (Tea)
With this method, water-saturated tea leaves are treated with carbon dioxide and compressed to 200 times normal atmospheric pressure. The carbon dioxide acts like a magnet and attracts the caffeine molecules, which is then removed. When the carbon dioxide has finished removing the caffeine, the leaves are dried. The carbon dioxide is then recycled and caffeine is sold for other commercial uses.
