The Science Behind Naturally Decaffeinated Tea
After several years of researching the pros and cons of various products and methods, we’re excited to be launching our first decaf tea Lemon Ginger Slimmer, which is 99% caffeine-free. The organic green tea base for this handcrafted blend has been through a supercritical carbon dioxide decaffeination, which we find to be the most natural, yet effective, method. This method, done under very high pressure (250 to 300 times atmospheric pressure) extracts almost all the caffeine from the tea leaves, but only about 10 percent of the antioxidant content.
The way our Decaf Tea works can be followed in my hand-written diagram below. At very high pressure, CO2 has a density resembling that of a liquid, but still diffuses like a gas. This is what’s called going into a supercritical state, at which it becomes a “super” solvent - being able to attract molecules and move them away rapidly, with very little pumping required.
Various decaffeination processes have been in development and production since the beginning of the 20th century, originally developed for coffee. The earliest method used benzene, which is a potentially toxic hydrocarbon, to extract caffeine from water-softened beans. Modern processes use gentler, less toxic solvents, but we didn’t wish to employ any chemical solvents in our tea. The best candidates from our perspective were a Swiss water extraction method and the supercritical CO2 method which we favored. Although pricier than the more conventional “naturally decaffeinated” solvent-based approaches, the high-pressure CO2 steam used on our green tea is entirely non-toxic, and best preserves the non-caffeine bioactive molecules (as well as the flavor!) in the tea leaf.
We did question whether CO2 is released into the atmosphere in the process. However, this is a closed-loop system. The “caffeinated” CO2 exiting the extraction vessel is routed through a bed of activated charcoal or a water 'bath' tower, which absorbs the caffeine. The CO2 is then recirculated back into the system for the next batch of decaffeination. The process has excellent yields, with very little (less than 1%) of the CO2 ultimately being released into the atmosphere. The caffeine byproduct is then sold to companies that produce caffeinated soft drinks, for example. And whether or not you're into those or not, it's admirable that the process is not wasteful.