How do they take the caffeine out of black tea? The Industrial Processes Explained

December 12, 2025 •

4 min read

Decaffeinated black tea has a significantly lower caffeine content—typically over 96% less than its regular counterpart, according to the British Heart Foundation. Unlike herbal infusions that are naturally caffeine-free, decaf black tea undergoes a specific manufacturing process to remove most of the stimulant from the tea leaves.

Quick Summary

This article explains the commercial methods used to decaffeinate black tea, focusing on the carbon dioxide, ethyl acetate, and water processes that extract caffeine from the leaves.

Key Points

Three Main Methods: The most common commercial methods for decaffeinating black tea are the CO2 process, the ethyl acetate method, and water processing.
Supercritical CO2 Process: This method uses high-pressure CO2 to extract caffeine selectively, preserving more of the tea's natural flavor and antioxidants, and is approved for organic products.
Solvent-Based Methods: Processes using chemicals like ethyl acetate or methylene chloride are less expensive but can sometimes leave a trace residue or slightly alter the tea's flavor.
Decaf is Not Caffeine-Free: Decaffeinated tea is never 100% caffeine-free, containing a trace amount (typically 2-10 mg per cup), unlike herbal teas which are naturally caffeine-free.
DIY Method is Ineffective: A quick rinse of tea leaves with hot water does not effectively decaffeinate the tea and will significantly reduce its flavor and health benefits.
Flavor and Health: The decaffeination process can slightly reduce the overall concentration of antioxidants, but much of the health benefits and flavor profile are retained, especially with methods like CO2.

Understanding the Decaffeination Process for Tea

The caffeine found in black tea is a natural compound within the leaves of the Camellia sinensis plant. To create a decaffeinated product, manufacturers must extract this compound after the tea leaves have been harvested and processed. While it's impossible to remove 100% of the caffeine, commercial decaf teas meet strict regulatory standards, ensuring the caffeine level is very low, typically below 0.4% by dry weight. The methods used are designed to be safe and to preserve as much of the tea's natural flavor and aroma as possible.

The Supercritical Carbon Dioxide (CO2) Method

Often considered the premium method for decaffeinating tea, the CO2 process is both highly effective and environmentally friendly. It is frequently used for organic and high-quality loose-leaf teas because it best preserves the complex flavor compounds.

The process works as follows:

Moistening: The tea leaves are first moistened with water and placed in a high-pressure vessel.
Pressure and Heat: Carbon dioxide gas is then subjected to high pressure and temperature, bringing it to a "supercritical" state where it behaves as both a gas and a liquid.
Caffeine Extraction: In this supercritical state, the CO2 acts as a solvent that selectively bonds with the small caffeine molecules, drawing them out of the tea leaves. Crucially, the larger flavor molecules remain intact.
Recycling the CO2: The caffeine-laden CO2 is then moved to a separate chamber where the pressure is released, causing the caffeine to separate. The CO2 can then be recycled for further use.
Drying: The now-decaffeinated tea leaves are dried and prepared for packaging.

The Ethyl Acetate Method

This method uses ethyl acetate, an organic compound found naturally in tea and various fruits, to extract caffeine. While it is considered a safe and effective method by regulatory bodies like the FDA, it has a few drawbacks.

The steps are similar to other solvent-based methods:

Moistening the Leaves: Tea leaves are moistened, often with steam, to prepare them for the process.
Soaking in Ethyl Acetate: The leaves are then soaked in ethyl acetate, which binds with the caffeine molecules.
Removing the Solvent: The tea leaves are then dried, and the ethyl acetate is removed. However, ethyl acetate is notoriously difficult to remove completely, and some residue can remain, leaving a slightly chemical or altered flavor profile in the final product.

The Methylene Chloride Method

Another solvent-based method, this process uses methylene chloride to bond with and remove caffeine. Although approved for use in many regions, including Europe, some consumers are cautious due to health concerns associated with the chemical. The tea leaves are rinsed thoroughly to remove residual solvent, and the process is known for effectively retaining the tea's flavor. Like other solvent methods, it leaves only trace amounts of the chemical.

The Water Processing Method

While more commonly used for coffee decaffeination, water processing is also an option for tea leaves. It avoids the use of chemical solvents entirely, though it can negatively impact the tea's flavor. A well-known version of this process is the Swiss Water Process, which uses green coffee extract to aid in decaffeination.

The general steps are as follows:

Hot Water Soak: Tea leaves are soaked in hot water to dissolve both caffeine and flavor compounds.
Filtering: The resulting water is passed through a carbon filter that specifically captures the caffeine molecules.
Reabsorption: The now caffeine-free but flavor-rich water is returned to the tea leaves, allowing them to reabsorb the flavor compounds lost in the initial soak.
Drying: The decaffeinated leaves are dried and packaged.

A Note on the 'At-Home' Decaf Method

Some believe that a quick 30-second rinse of black tea leaves with boiling water can remove a significant portion of the caffeine. However, this is largely a myth. Studies show it takes a much longer period, around six minutes, to remove a substantial amount of caffeine, but by then, the tea's desirable flavor and antioxidants have also been rinsed away. Commercial decaffeination requires far more complex, precise processes than a simple rinse. For a truly low-caffeine drink, commercially decaffeinated products are the most reliable option.

Comparison of Decaffeination Methods


Feature	Supercritical CO2 Method	Ethyl Acetate Method	Water Processing Method
Chemicals Used	None, uses natural CO2 gas.	Ethyl Acetate, an organic solvent.	None, uses water and activated carbon filters.
Flavor Retention	Excellent, as flavor molecules are larger and not affected.	Good, but can leave a slight aftertaste if residue remains.	Fair, can sometimes lead to a milder or watery flavor.
Cost	More expensive due to the specialized equipment required.	Less expensive, making it common for commercial teas.	Varies, can be more expensive than solvent methods.
Effectiveness	Highly effective, removing up to 97-99% of caffeine.	Effective, though potentially less precise than the CO2 method.	Effective, removing a high percentage of caffeine.
Health & Safety	Widely considered the safest method; approved for organic products.	Considered safe by regulators due to residual limits, though some consumers are wary.	Considered safe due to the absence of chemical solvents.

Decaf vs. Naturally Caffeine-Free

When choosing a beverage, it's important to distinguish between decaffeinated and naturally caffeine-free teas. Decaffeinated black tea has been processed to reduce its caffeine content, meaning it still contains trace amounts. In contrast, herbal teas like rooibos, chamomile, and peppermint are made from plants that naturally contain no caffeine at all, making them truly caffeine-free.

Conclusion

The commercial decaffeination of black tea is a sophisticated process that relies on a handful of proven methods. From the chemical-free, high-quality Supercritical CO2 method to the more common Ethyl Acetate process and the water-based techniques, each approach has its own impact on the final product's flavor profile. While no decaf product is completely caffeine-free, these processes successfully remove the vast majority of the stimulant, offering a popular alternative for those who wish to reduce their caffeine intake without giving up the rich taste of black tea.

For more detailed information on decaffeination, consult reputable sources like the Swiss Water Process website: Swiss Water Process.

Frequently Asked Questions

Yes, decaffeinated black tea is not completely caffeine-free. While the decaffeination process removes most of the caffeine (up to 99%), trace amounts, typically 2-10 mg per cup, will remain.

Decaf tea is made from tea leaves that naturally contain caffeine but have undergone a process to remove most of it. Caffeine-free teas, such as herbal infusions like rooibos or chamomile, are made from plants that never contained caffeine to begin with.

The ethyl acetate method is regulated and considered safe by agencies like the FDA in the US, with strict limits on residual solvent levels. Some consumers prefer to avoid it in favor of solvent-free methods like the CO2 process.

The Supercritical CO2 method is widely regarded as the best for preserving the tea's flavor. It selectively removes the smaller caffeine molecules while leaving the larger flavor compounds intact.

The decaffeination process can remove some of the tea's antioxidant compounds, but a significant amount is retained. While the overall concentration may be slightly lower than in regular tea, decaf tea still provides health benefits.

No, the popular home-decaffeination myth of rinsing tea leaves with boiling water is largely ineffective. It fails to remove significant amounts of caffeine and sacrifices a great deal of the tea's flavor and beneficial compounds in the process.

Yes, water processing is used for some decaffeinated black teas, though it is more commonly associated with coffee decaffeination. It is a chemical-free process but may result in a less robust flavor profile compared to other methods.