Shaky grounds: the pharmacology of coffee

Common Names: Coffee. Kahvey. Java. Crank. Bean. Joe. Go Juice. Ambition.

Taxonomy: The genus Coffea is part of the Rubiaceae, one of the largest families of flowering plants, including gardenias. The family is widely represented in the tropics, where it occurs as trees or shrubs.

Alkaloids are common throughout the family. Only two Coffea species are widely cultivated: Coffea arabica and Coffea canephora, known in the trade as robusta.

The best coffee comes from Coffea arabica, the original source of the highly prized beans. Wild populations are very difficult to find, and even those few that are found to be growing without human aid are probably feral.

The highlands of southwestern Ethiopia are considered to be the original homeland of Coffea arabica, and that is where its greatest genetic diversity is found. While the flower is fully capable of cross-fertilization, the tree is so self-compatible that the majority of the fruits are usually self-fertilized.

Since the middle of the nineteenth century, explorers and botanists have discovered scores of truly wild species of Coffea in the mountains of tropical Africa and Madagascar. The Madagascar coffees have been isolated from Africa since the Cretaceous era and are most distinctive from their African relations by their lack of caffeine. Nonetheless, the Madagascar coffees and a number of the African species can still hybridize.

Part Used: The seeds, mostly. In Arabia the pulp is fermented into an alcoholic beverage. In Malaysia and Indonesia, and in some parts of Latin America, the leaves are used to brew a tea.

Chemistry: The principal alkaloid is caffeine. Two related xanthines, theobromine and theophylline, are often present in smaller amounts.

Caffeine occurs in the leaves as well as in the seeds. The caffeine content of green Coffea arabica beans varies between 0.6 and 1.6 percent. The caffeine content of robusta is higher, usually between 1.2 and 3.2. percent. However, robusta lacks many of the flavorings found in arabica, so is most often used for extracts and instant coffees.

In addition to the alkaloids, the beans contain trigonelline, amino acids, proteins, enzymes, carbohydrates, polysaccharides, quinic and associated chlorogenic acids, oils, a wax that coats the bean, a few pigments, and at least 180 volatile compounds.

Roasting alters the chemistry significantly, of course. Around ten percent of the caffeine vaporizes, even more in a darker roast. Perhaps the greatest effect of roasting is on the carbohydrates, which are highly pyrolized (i.e., burned--Ed.). Roasting also destroys most of the trigonelline, converting it into nicotinic acid (niacin), nicotinamide, and a score of volatile aromatics. Most of the volatile compounds remain trapped within the beans.

Chemists, in partnership with trained coffee tasters, have been able to identify and characterize an astonishingly large number of the flavor constituents of coffee. Like wine tasters, coffee tasters have developed a specialized vocabulary to analyze the complex flavors and feel of a cup of coffee. "Acidity" is distinguished from "sourness," and "bitterness" is distinguished from "astringency" (though molecules that are astringent are sometimes also bitter). Humans have no taste receptor for astringency, but the chemists have been able to correlate astringency with a molecule's ability to precipitate salivary proteins and glycoproteins.

Investigations indicate that the astringency in coffee, especially that with a "metallic" aftertaste, seems to correlate with the relative quantities of caffeoylquinic and dicaffeoylquinic acids in the bean.

On the chemical side, analyses have been made on scores of compounds contributing to the coffee aroma. Many of the breakdown pathways from precursor compounds in the green bean to the compounds found in the roasted bean have also been traced. But because of the sheer number of compounds involved, and synthetic reactions occurring among the breakdown products, the chemists are quick to admit these exercises as yet have little predictive value in determining which green bean will develop what particular flavors.

The character of "body," the mouthfeel of coffee, has proved chemically elusive. It has been demonstrated that there is no simple relationship between body and viscosity. Experiments suggest complex interactions between bitterness receptor sites, astringent phenols that could bind to them, and salivary proteins. At present, "body" is still the venue of the tasters, as is detecting subtle differences between "papery" and "woody," "grassy" and "green," and "earthy," "bricky," and "cereal."

Snore.

No. Wake up now. Have a cup of coffee.

How Taken: The oldest method is probably chewing the seeds. In Ethiopia the beans are cooked in butter and made into cakes. In Yemen and other Arab countries the seeds are ground by the woman of the house in the morning by pounding. This sometimes creates problems for people living in apartments. Before the coffee may be drunk the preparation of the coffee must be praised by the eldest male.

Effects: To spare spouses and others from being cursed first thing in the morning, which impulse is itself at least partially the result of the coffee you drank yesterday.

The Plant: Coffee grows naturally as an understory plant in the tropics as a shrub or small tree. It can grow to a height of over twelve feet, but is usually pruned in ways that increase its bushiness, leafiness, and ease of harvesting. The white flowers give off a delicate fragrance.

Until recently, nearly all coffee was grown in the shade, in conditions mimicking its natural environment. Growers plant as many as forty different kinds of trees as canopy cover, and a rich ecosystem develops, with epiphytes, mosses, birds, and other wildlife. Today more and more coffee is being grown in cleared "sun plantations." While these sun plantations are better suited to the capital-and fertilizer-intensive methods of agribusiness, they offer no habitat for the hundreds of birds, the innumerable insects, and the other animals found in the traditional farms.

Odd calling a coffee plantation "traditional."

In the cleared plantations, special care has to be taken to protect young plants from the excess of sunlight. Lack of biological insect control necessitates using more pesticides, as lack of humus and plant litter necessitates using more chemical fertilizers. The result is that sun grown coffee beans are more expensive by the pound to produce than shade grown coffee, even though the yield per acre is higher. If you can buy shade grown coffee, do so.

The cover trees used in shade plantations often include species of Acacia, Cassia, and Erythrina. And since Salvia divinorum grows well under coffee trees, certain three-level plantation designs come to mind that could be highly viable both ecologically and spiritually, as well as economically.

How Taken: As a beverage, in a cup, extracted with hot water by refluxing ("percolated coffee"), by percolating ("drip coffee"), or by decoction ("campfire coffee").

Drunk in a demitasse, as espresso. With milk, as cafe au lait or caffe latte. With steamed milk with foam on top, as cappuccino. From a styrofoam cup, at public meetings. From a thermos, directly.

On occasion, squirted through a rubber tube and plastic syringe, as a colonic enema.

Adapted with permission from Pharmako/Dynamis (2002; Mercury House; see review, page 38).

COPYRIGHT 2002 Point Foundation
COPYRIGHT 2002 Gale Group