Dario Bressanini [Le Scienze 455]
Consumed by millions of people every morning, coffee is part of the same group of natural substances of nicotine and cocaine. But, fortunately, is much less harmful
What is the substance, a relative of morphine, which take millions of Italians every morning to start your day? No, no joke: it is the caffeine. Its full chemical name is 1,3,7-TRIMETILXANTINA and belongs to the large group of natural substances called alkaloids. This group includes other well-known substances, and toxic substances such as nicotine and cocaine. Most alkaloids have a physiological effect, and since ancient times were used extracts from plants containing alkaloids for medicinal purposes, or as poisons. It was the coniina alkaloid extract of hemlock, for example, to kill Socrates. Even caffeine is toxic, but only in large quantities: the lethal dose is estimated to be about ten grams, or the equivalent of 100 to 200 cups of coffee '. Caffeine is a stimulant of the central nervous system. But the body does not accumulate, and thrown them away fast enough. Nerve cells mixed with caffeine, adenosine, due to similar chemical structure. When adenosine binds to a receptor in a cell 
nervous cause drowsiness. Caffeine, "cheats" the cell by binding to adenosine receptors, but without causing drowsiness.
The "discovery" of coffee is lost in the mists of time. According to legend, the shrub grows wild in Ethiopia. A shepherd discovered it by observing the effects that his sheep did not sleep more after the fruits of cibate quell'arbusto. The coffee arrives in Venice at the beginning of the seventeenth century, and from there spread throughout Europe. Caffeine was first extracted from coffee beans in 1819. The same substance, isolated from tea leaves in 1827, was named theine. Only after they realized that the chemical protein and caffeine were, in fact, same molecule. Many will be surprised to know that caffeine is a white crystalline powder, bitter, and is not responsible for the aroma and taste of coffee, which are derived from an amazing mixture of substances present in the grain complex, other varieties' a variety '. it is only after the roasting of green beans at temperatures above 200 degrees, that coffee 'buy aroma and color we're used to. The roasting drastically alters the chemical composition of beans: protein and sugars that are contained react in the Maillard reaction, forming hundreds of 
volatile compounds that give coffee roasted to the color and the characteristic aroma. But then, 'cause decaffeinated coffee has a different taste? Due to the process of extraction of caffeine from the beans with various solvents are still green. Organic solvents such as ethyl acetate or dichloromethane, unfortunately also extracted part of substances responsible for the aroma of coffee '. The modern decaffeination processes, based on water or CO 2 , are more careful not to remove the substances responsible for the aroma from the beans. Caffeine is not removed completely, but it is still up 0.1 percent. During the preparation of espresso, a small amount of hot water at high pressure is rapidly in contact with the ground coffee, extracting the aromatic substances. 
The rapidity of the process makes a cup of espresso contains less caffeine than a prepared with the coffee pot (about 80 milligrams versus 150). In addition, unlike other methods of preparation, espresso contains fats that create tiny droplets of essential oils that attach to the tongue and palate and espresso give the typical feeling of creaminess'. that's why the taste of espresso persists longer in the mouth, and is more effective to remove the milk of water, the greater affinity with fat.
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