How do they de-caffeinate tea?

[WILLASS]

I recently bought two types of Earl Grey tea, one de-caffeinated and one not. Now they both taste almost identical (the de-caffeinated tastes better IMHO) which got me to wondering how they extract the caffeine without adversely affecting the taste, anyone know how this is done?

[Q.E.D]

Apparently, there are three different processes in common commercial use:

The three most widely used methods used to decaffeinate tea (and coffee) are carbon dioxide, water, and ethyl acetate. With each of these processes, there are significant differences in the taste, the residual chemicals, and in the environmental repercussions. It is also important to remember that in any decaffeination process, some amount of caffeine may remain, and the level of antioxidants and other health promoting components can be impacted by the extraction.

From here. I also found this which describes a version of the water process you can use at home to decaffeinate tea.

[Napier]

At least a few years ago, the “carbon dioxide method” (more commonly known as carbon dioxide supercritical fluid extraction) was a/the popular method for decaffienating coffee, and it should work also for tea. I’m gonna bet that’s the method they use.

Supercritical fluids are fluids whose temperature and pressure are higher than the critical temperature and critical pressure for that substance. What they teach us in elementary school about there only being solids, liquids, and gasses is incorrect. One of the things they left out is supercritical fluids. They have densities intermediate between gasses and liquids, and like liquids they can dissolve things. But like gasses they permeate through powdery or fibrous materials without any surface tension effects making it harder to get in there or, worse, completely get back out again.

The beauty of SFE is that every substance that the fluid will dissolve, it can only dissolve above some “threshold pressure”. So, you can decaffienate coffee (and presumably tea) by slowly going up to caffiene’s threshold pressure while you capture and hold all the flavors etc with lower threshold pressures, and then you’d go past the threshold pressure of caffiene and catch and separate it, and finally you’d go back down in pressure and mix back in all the flavors etc that you had taken out before.

Supercritical carbon dioxide must be kind of warm and must be a few thousand psi in pressure. The temperature is quite compatible with many foods and biological compounds. You can also do tricks, like shrinking dollar bills to about 2/3 of their original size. Although I worked with it a few years ago, I don’t remember the critical point - but you need special pumps and heavy components to handle it, and the tanks are quite massive. Autoclave Engineers of Erie, PA is a major maker of this equipment.