Decaffeinated Coffee: Introduction

Technology is always trying to give us back the garden without the snake. So you like coffee and not caffeine? Well, then, we will take out the caffeine and leave you your pleasure, intact.

Decaffeinated coffee is indeed without venom. It contains, at most, one fortieth of the amount of caffeine in untreated beans. Nor should the removal of caffeine alter the taste of coffee. Isolated, caffeine is a crystalline substance lacking aroma and possessing only the slightest bitter taste. Its flavor is lost in the heady perfumes of fresh coffee. So if you hear people say, "Coffee doesn't taste like coffee without the caffeine," they are wrong. The only real problem is how to take out the caffeine without ruining the rest of what does influence coffee flavor. But technology has triumphed, more or less. The best decaffeinated coffee, freshly roasted and ground and carefully brewed, can taste so nearly the equal of a similar untreated coffee that only a tasting involving direct comparison reveals the difference.

Unfortunately, fine decaffeinated coffees are the exception rather than the norm. Decaffeinated beans are notoriously difficult to roast, so even the best decaffeinated beans may produce a thin-bodied, half-burned cup once they are roasted. Still, for the coffee devotee even listless decaffeinated coffee is better than mint tea, and you can always compromise and spruce up a caffeine-free coffee by adding a little full-bodied caffeinated coffee before grinding it, or by creating your own low-caffeine blend.

Most caffeine-free coffee sold in specialty stores is shipped from the growing countries to decaffeinating plants in Europe or Canada, treated to remove the caffeine, then re-dried and shipped to the United States.

Coffee is decaffeinated in its green state, before the delicate oils are developed through roasting. Hundreds of patents exist for decaffeination processes, but only a few are actually used. They divide roughly into those that use a solvent to dissolve the caffeine, those that use water and charcoal filters, and those that use a special form of carbon dioxide.

Solvent Method

The direct solvent method is the oldest and most common decaffeination process. On coffee signs and bags it is typically not identified at all, or called by various euphemisms like European or traditional process. The beans are first steamed to open their pores, then soaked in an organic solvent that selectively unites with the caffeine. The beans are then steamed again to remove the solvent residues, dried, and roasted like any other green coffee.

A more recently developed process called the indirect solvent method starts by soaking green beans in near-boiling water for several hours. The water is transferred to another tank, where it is combined with a solvent that selectively absorbs most of the caffeine. The caffeine-laden solvent is then skimmed from the water, with which it has never really mixed. The water, now free of both caffeine and solvent, still contains oils and other materials important to flavor. In order to return these substances to the beans, the water is returned to the first tank, where the beans reabsorb the flavor-bearing substances from the water.

What About the Solvents? The joker in the process is still the solvent. People concerned about the effects of coffee on their health obviously are not going to feel comfortable purchasing a product containing even minute traces of solvent. In 1975 one of the most widely used solvents, trichloroethylene, was named a probable cause of cancer in a "Cancer Alert" issued in 1975 by the National Cancer Institute.

Also, no one knows how much of the solvent residue -- if any -- is retained in the brewing process and ends up in the cup. Given the volatility of the solvent and the relatively minuscule amount left in the bean after roasting, it is most likely that none whatsoever ends up in the coffee we ultimately consume.

A New and Better Solvent: Methylene Chloride. Nevertheless, the news that the caffeine that some feared caused heart disease was being replaced by a solvent that actually did cause cancer provoked understandable consternation among health-conscious consumers.

The coffee industry promptly responded by replacing trichloroethylene with methylene chloride, a solvent not implicated in the National Cancer Institute study. So far tests of methylene chloride have not linked it to any known disease, and given its volatility (it vaporizes at 104° F; coffee is roasted at over 400° F for at least 15 minutes, then brewed at 200° F) it seems hardly possible that any of the 1 part per million occasionally found in the green beans could end up in the consumer's cup or stomach.

An Even Newer and Better Solvent. A second solvent is now in use in some European decaffeination plants: ethyl acetate. Like methylene chloride, ethyl acetate has not been implicated in any diseases, and environmentalists consider it more benign than methylene chloride. Because ethyl acetate is derived from fruit, some publicists and brochure writers have taken to calling coffees decaffeinated using ethyl acetate "naturally decaffeinated," and you may see them so advertised.

Swiss Water Process

In the 1980s the Swiss firm Coffex S.A. developed a commercially viable decaffeination process using water only -- no solvents whatsoever. As in the indirect solvent or solvent/water process described earlier, the various chemical constituents of the green coffee, including the caffeine, are first removed by soaking the beans in very hot water.

In the Swiss Water Process, however, the water is stripped of its caffeine, not by a solvent, but by percolation through activated charcoal. (It really ought to be called the Swiss Charcoal Process.) The beans are returned to the hot water, where they reabsorb the remaining, caffeine-free flavor constituents from the water.

This process is more costly than the solvent process because the separated caffeine cannot be recovered from the charcoal and sold separately, as it is with the two solvent methods. It is also controversial in terms of flavor. Many coffee professionals contend that the Swiss Water Process blurs flavor more than the competing solvent processes. However, the management of the Canadian plant that currently produces all of the Swiss Water Decaffeinated coffees sold in North America continues to make determined efforts to refine and improve the process.

Carbon Dioxide Methods

Decaffeination processes using carbon dioxide (CO2) differ in their details. All take advantage of the fact that carbon dioxide, when compressed, behaves partly like a gas and partly like a liquid, and has the property of combining selectively with caffeine. In the most widely used CO2 process the steamed beans are bathed in the compressed carbon dioxide and the caffeine is removed from the carbon dioxide through charcoal filtering, just as it is in the water-only process. However, the flavor components remain in the bean throughout the process, rather than being soaked out and then put back in again, as they are in both the Swiss Water and the indirect solvent processes.

Since carbon dioxide is the same ubiquitous and undisputably "natural" substance that plants absorb and humans produce, and since, in most versions of the CO2 method, the flavor components remain safely in the bean throughout the process rather than being removed and put back in again as they are in the Swiss Water process, carbon dioxide methods would seem to be the decaffeinating wave of the future. However, coffees decaffeinated by the CO2 method have been slow to come onto the specialty market, and reviews have been mixed.

Decaffeination Methods and Flavor

Which decaffeination method produces better tasting coffees? It is difficult to say for certain for two reasons. First, it is virtually impossible to turn up the identical coffee decaffeinated by a range of different methods, and the quality of the original coffee obviously influences the quality of the final cup. Second, decaffeinated coffees are difficult to roast properly, and subtle differences in decaffeination method may be overwhelmed by differences in the quality of the roast.

Nevertheless, my own experience clearly and consistently indicates that the Swiss Water Process tends to emphasize body, de-emphasize acidity and high notes, and occasionally (but not always) alter or blur flavor, whereas the European or solvent method tends to preserve acidity, nuance, and high notes, but may reduce body and dimension. As for coffees processed using the CO2 method, I have tasted some excellent samples, but not enough of them to generalize.