What the operation is doing to the leaf
Decaffeination is an extraction applied to finished or semi-finished tea. The leaf is moistened or otherwise prepared so that its soluble contents can move, a solvent is brought into contact with it, the solvent takes up caffeine along with whatever else it has an affinity for, and the leaf is then dried again. Every method shares that shape and they differ in the solvent and in the selectivity. Three points follow that a buyer should hold before any comparison between methods. No process removes caffeine completely; what is produced is tea with much less of it, and the residual amount depends on the process, the leaf and how far the operation was run. Every process removes other things as well, because no solvent takes only one compound, and the fraction most affected is the volatile aromatic material that carries a tea’s character. And the leaf is wetted and dried again, which is a physical stress on material that was carefully dried once already. This page describes those processes as facts about the leaf and about manufacture. What caffeine does to a person is a different subject, governed elsewhere in this catalogue under a different standard of evidence, and nothing here addresses it.
Carbon dioxide
The method most often described as the gentlest. Carbon dioxide held above its critical point behaves as a fluid with properties between a gas and a liquid, and in that state it is a solvent with a useful selectivity: it takes up caffeine readily and takes up rather less of the larger flavour-bearing compounds than an organic solvent would. The gas is then depressurised, the caffeine separates out and is recovered as a saleable by-product, and the leaf is dried. The equipment operates at high pressure and is expensive, which is the main reason the method is not universal. As a manufacturing fact this is the process most associated with retaining the character of the original tea, and the retention is relative rather than complete — a carbon-dioxide-processed tea is still recognisably a decaffeinated tea to anybody who compares it against the same leaf untreated. Labels do not always name the method, and where a pack says only that the tea has been decaffeinated the process is unstated; where it names carbon dioxide, it is describing a specific and comparatively costly operation, which is one of the few genuinely informative process statements available in this part of the market.
Ethyl acetate, and the phrase that attaches to it
Ethyl acetate is an organic solvent that occurs in various fruits and is also produced synthetically, and it is used in decaffeination by direct contact with the moistened leaf. Because the compound occurs in nature, tea processed this way is frequently described as naturally decaffeinated, which is a phrase worth unpicking. It is a claim about the origin and classification of the solvent rather than about the process being gentle, and the process itself is a solvent extraction like any other. Ethyl acetate is generally reported as less selective than carbon dioxide, taking more of the flavour-bearing material with the caffeine and leaving a characteristic note of its own that some drinkers detect and others do not. The method is cheaper, which is why it is common. None of this is an accusation: the operation is a standard one, the label term has a defensible basis, and the resulting tea is what a great many decaffeinated products are. The point is narrower and it is the recurring point of this whole file — the word natural on a label describes how a substance was obtained rather than what it is or how good the result tastes.
Water-based processes
Water extraction removes caffeine without any organic solvent by exploiting the fact that a water extract already saturated with a tea’s other solubles will take up caffeine preferentially, so the flavour-bearing compounds have less tendency to leave the leaf. In practice this involves an extract and a filtration or adsorption step that removes the caffeine from the water, after which the water is returned to the leaf. Variants of the approach exist under several proprietary and generic names, and water-process products are sometimes described using the same natural vocabulary as ethyl acetate ones, which is one more reason a label term does not settle which method was used. The trade-off is that water is a broad solvent, so keeping the flavour compounds in the leaf depends entirely on the extract-saturation step working well; where it does the result can be good, and where it does not the tea is noticeably hollow. As with the other methods, the honest summary is that all three remove more than caffeine, they differ in how much and in what, and no method returns a decaffeinated tea to the leaf it was made from.
What to expect in the cup, and what to buy instead
A decaffeinated tea is generally lighter in aroma, shorter in the finish and softer in structure than the same leaf untreated, because the operation takes some of the aromatic fraction and some of the compounds associated with grip along with its target. Producers respond by starting from robust material, which is why most decaffeinated tea is black tea and why decaffeinated green tea is comparatively rare and comparatively disappointing. Two practical implications. Judge a decaffeinated tea against other decaffeinated teas rather than against the original, since the comparison against the original will always disappoint and tells you nothing about which of the available products is good. And consider the alternatives, which are genuinely different products rather than compromises: the herbal and botanical infusions that never contained caffeine at all, and the roasted grain drinks, are their own category with their own merits and this catalogue covers them at length. Choosing between a decaffeinated tea and a botanical infusion is a choice between two different drinks rather than two attempts at the same one.
What the label does and does not tell you
Frequently very little. A pack may state that the tea is decaffeinated without naming a method; it may use a natural or naturally decaffeinated phrasing that is compatible with more than one process; and it may or may not carry a statement about residual caffeine. TeaHQ does not state any threshold, any permitted residual level or any labelling requirement, because these differ between markets, are revised, and have not been verified here. Nor does the catalogue publish residual figures for decaffeinated teas, for the same reason it refuses any caffeine figure without a five-part basis stating leaf quantity, water volume, temperature, steep time and infusion number: a number without its basis cannot be checked, reproduced or compared. What a buyer can reasonably do is ask, since the importer or packer knows the process and will usually say. A seller who names the method is describing the product; one who offers only the word decaffeinated has left the informative field blank, which is the same observation this file makes about every other voluntary field on a packet.