Coffee contains a complex mixture of chemical compounds. Some components, particularly those related to the aroma, are produced during roasting of the green beans. The substances which during “”brewing”” dissolve in water to form the beverage are classified as nonvolatile taste components (including caffeine, trigonelline, chlorogenic acid, phenolic acids, amino acids, carbohydrates, and minerals) and volatile aroma components including organic acids, aldehydes, ketones, esters, amines, and mercaptans.
The major physiologically active substance in coffee is the alkaloid caffeine (C_8 H_10 O_2 N_4•H_2 O), also called guaranine or methyltheobromine, which acts as a mild stimulant. Caffeine is a naturally occurring substance found in the leaves, seeds or fruits of more than 60 plants, including coffee and cocoa beans, cola nuts and tea leaves. These are used to make beverages such as coffee, tea and cola drinks, and foods such as chocolate. Caffeine is also contained in many over-the-counter (OTC) and prescription medications. In the United States, most of the population uses caffeine in some form.
A cup of coffee, depending on the strength, may contain some 20-100mg of caffeine. Some types of coffee may also contain significant amounts of the B-vitamin niacin, although this nutrient is of course readily available from other foods as well. Caffeine-containing tablets or medications should not be taken as well as cups of coffee or tea, since this would increase the true dosage. The effects of caffeine vary from person to person; some individuals can drink several cups of coffee in an hour and notice no effects, while others may feel a strong effect after just one serving. Caffeine is prohibited for competition athletes.
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