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Decaf tea: how caffeine is removed from the leaf

For many people decaffeinated tea is a way to enjoy their favourite brew in the evening, without fear of insomnia. But how exactly is such tea made? Caffeine is a natural component of the tea leaf, so it has to be removed from it - and that is not simple. There are four main methods of decaffeination, each of a different principle of action and a different influence on flavour: carbon dioxide, ethyl acetate, water and methylene chloride. Importantly, none of them removes caffeine one hundred percent. In this post you will get to know all four methods, learn how they work, how they affect the flavour of tea and why decaf is never entirely caffeine-free. It is a journey into the process that stands behind every cup of decaffeinated tea. Let us start with why caffeine is removed at all.

Why remove caffeine

Caffeine is a natural component of the tea leaf, giving stimulation and alertness. For many people it is an advantage, but for others a reason to avoid tea, especially in the evening. Decaffeinated tea lets you enjoy the flavour and ritual of drinking tea without the effects of caffeine: without the risk of insomnia, palpitations or anxiety in sensitive people. It is an option for those who love tea, but have to or want to limit caffeine - for reasons of health, sensitivity, pregnancy or simply the time of day. Decaffeination is an industrial process that removes most of the caffeine from the leaf, keeping the flavour and aroma as far as possible. The goal is clear: to give a tea that tastes like tea, but does not stimulate. It is a challenge, because caffeine is interwoven with the structure and flavour of the leaf. Removing it without destroying the tea requires thought-out methods. So let us get to know the four main methods, starting with the most modern - carbon dioxide.

The carbon dioxide method

The CO2 method is one of the most modern and most valued techniques of decaffeination. In this method tea is subjected to the action of carbon dioxide under high pressure and at high temperature, at which CO2 reaches a supercritical state - something between a gas and a liquid. In this state carbon dioxide bonds with the caffeine molecules, largely ignoring the compounds responsible for flavour and aroma. It is a key advantage: the CO2 method selectively removes caffeine, leaving the flavour largely intact. After flowing through the tea, the caffeine-laden carbon dioxide is filtered to strip out the caffeine, then recycled for another use. A full extraction cycle can take from one to five hours, depending on the size of the batch and the target level of caffeine. The CO2 method is valued for keeping the flavour well and leaving no chemical residues. That is why it is considered one of the best. Carbon dioxide is natural and safe, which makes this method popular in high-quality decaffeinated teas.

The ethyl acetate method

The ethyl acetate method is often called natural decaffeination, because ethyl acetate is a compound that occurs naturally in tea and fruit. In this method caffeine is extracted similarly to using methylene chloride, but the solvent is ethyl acetate. The tea leaves are subjected to the action of this solvent, which bonds with and washes out the caffeine. The name natural sounds attractive for marketing, but it has its catches. Ethyl acetate is difficult to remove completely after the decaffeination process and is sometimes described as leaving a slightly chemical taste. It is the main flaw of this method: although effective and relatively cheap, it can affect the flavour of tea more than the CO2 method. The term natural refers to the origin of the solvent, and not to a lack of interference with flavour. The ethyl acetate method is widely used because of cost and effectiveness, but purists rate it lower than CO2. It is a compromise between price and keeping the flavour. It is worth knowing what hides behind the label naturally decaffeinated.

The water method

The water method is probably the simplest and most natural process of decaffeination, because it uses no chemical solvents. In this method tea is steeped in hot water, which washes the caffeine out of the leaf, but also the flavour and aromas. Then this water is passed through a carbon filter, which catches the caffeine molecules, but lets the flavour compounds through. The caffeine-free water, still carrying flavour, is returned to the tea leaves, so they reabsorb their flavours and oils. It is an elegant solution that avoids chemistry. Its flaw, however, is that it usually leads to a noticeable loss of flavour in most teas - the process of washing out and reabsorbing is never perfect. The water method is valued by those who want to avoid solvents, but at the cost of part of the aroma. It is a choice for those seeking the most natural process, willing to accept a certain flavour compromise. The water method shows that the less chemistry, the harder it is to keep the full flavour.

The methylene chloride method

The methylene chloride (dichloromethane) method is one of the traditional techniques of decaffeination, based on a chemical solvent. In this method caffeine molecules bond with molecules of methylene chloride, which washes them out. In the indirect variant the tea is first steeped in hot water to release the caffeine, and the leaves are removed; then methylene chloride extracts the caffeine from the water, after which the flavoured water returns to the leaves. This method is effective and keeps the flavour well, which is why it was and is widely used. Its controversy results from the use of a chemical solvent, although in the finished product the residues are minimal and within safety norms. Despite this, some consumers prefer to avoid this method, preferring CO2 or water. The methylene chloride method is a classic compromise between effectiveness and the perception of chemistry. Effective and cheap, it nonetheless raises doubts of an image nature. It is worth knowing that it is one of the options, although labels do not always indicate it directly. It is a method for effectiveness, not necessarily for peace of mind.

The influence on flavour

The influence of decaffeination on the flavour of tea depends on the method used. No process is completely neutral for the aroma, because caffeine is interwoven with the structure of the leaf flavour, and removing it, it is hard not to disturb other compounds. The CO2 method usually keeps the flavour best, because it selectively bonds the caffeine, largely ignoring the aroma compounds. The ethyl acetate method can leave a slightly chemical taste. The water method usually leads to a noticeable loss of flavour, despite returning the flavour compounds. The methylene chloride method keeps the flavour well, but raises doubts about chemistry. In general decaffeinated tea is sometimes a little less intense and complex than its caffeinated counterpart, although good decaffeination minimises this difference. It is worth remembering that the quality of the starting tea also matters - a good tea decaffeinated by the CO2 method can be quite satisfying. The choice of method is a compromise between keeping the flavour and other considerations. We write more about the role of caffeine in our post on caffeine in tea.

Decaf is not zero caffeine

An important truth that many do not know: decaffeinated tea is not entirely free of caffeine. None of the methods of decaffeination removes caffeine one hundred percent - a trace amount always remains. The term decaffeinated or decaf means that most of the caffeine was removed, usually over 97 percent, but not all. This means that people extremely sensitive to caffeine or having to avoid it entirely should know this - a cup of decaffeinated tea still contains a small amount of caffeine. For most people this residual amount is insignificant and does not cause stimulating effects, which is why decaf works great in the evening. But the difference between decaffeinated and entirely caffeine-free is real and worth knowing. Teas entirely free of caffeine are rather herbal infusions (tisanes), which never contained it, and not decaffeinated tea from the tea plant. Understanding this difference lets you make a conscious choice. Decaf is little caffeine, but not zero.

Decaffeination methods in a table

Let us set the four main methods of removing caffeine side by side:

The table shows that each method is a different compromise. CO2 protects the flavour best, but is more expensive. Ethyl acetate is natural in origin, but can leave a taste. Water avoids chemistry, but at the cost of aroma. Methylene chloride keeps the flavour, but raises doubts. None removes caffeine one hundred percent. The choice of method depends on the priorities of the producer and the expectations of the consumer. It is proof that behind the simple label decaffeinated hides a complex technology.

The key points in a nutshell

Decaffeinated tea is made by removing caffeine from the leaf by one of four methods. The CO2 method, using supercritical carbon dioxide, keeps the flavour best, because it selectively bonds the caffeine. The ethyl acetate method is natural in the origin of the solvent, but can leave a slightly chemical taste. The water method avoids chemistry, washing out the caffeine and passing the water through a carbon filter, but usually at the cost of part of the flavour. The methylene chloride method is effective and keeps the flavour well, but raises doubts about chemistry. Importantly, no method removes caffeine one hundred percent - decaf is little caffeine, but not zero. Want to compare caffeinated and decaffeinated teas and record your impressions? Keep tasting notes in the GustoNote app. See also our posts on caffeine in tea and on theanine, caffeine and catechins.