It's Espresso,
NOT "Expresso"!


The origin of the term "espresso" is the subject of considerable debate. Although some Anglo-American dictionaries simply refer to "pressed-out" (rooted in the Latin origin of the word), "espresso", much like the English word "express", also carries the meanings of "just for you" and "quickly," both of which can be related to the method of espresso preparation. The Italian spelling of the word is not "expresso", though that form is accepted by some English-language dictionaries (e.g. Merriam Webster). In an Italian coffee bar, as in much of Europe, ordering "a coffee" (un caffè in Italian), means just ordering an espresso. In France, the term café is normally used as well, but the French café is usually dark roasted.

Espresso or caffè espresso is a concentrated coffee beverage brewed by forcing very hot, but not boiling water under high pressure through coffee that has been ground to a consistency between extremely fine and powder.

Espresso was developed in Milan, Italy in the early 20th century, but up until the mid-1940s it was a beverage produced solely with steam pressure. The invention of the spring piston lever machine and its subsequent commercial success changed espresso into the beverage we know today. Espresso is now produced with between 9 and 18 atmospheres or bars (0.9 to 1.8 megapascals) of pressure.

The defining characteristics of espresso include a thicker consistency than drip coffee, a higher amount of dissolved solids than drip coffee per relative volume, and a serving size that is usually measured in shots, which is about 30 ml (1 fluid ounce) in size.

Espresso is chemically complex and volatile, with many of its chemical components quickly degrading from oxidation or loss of temperature. Properly brewed espresso has three major parts: the heart, body, and the most distinguishing factor, the presence of crema, a reddish-brown foam that floats on the surface of the espresso. It is composed of vegetable oils, proteins and sugars. Crema has elements of both emulsion and foam colloid.
As a result of the high-pressure brewing process, all of the flavors and chemicals in a typical cup of coffee are concentrated.

Because of its intense and high concentration of ingredients (including caffeine), espresso lends itself to mixing into other coffee based drinks, such as lattes, cappuccini, macchiato and mochas, without being diluted in the resulting drink.

There is a good deal of confusion about whether an espresso contains more or less caffeine than other typical servings of coffee. The confusion is understandable. On a per-volume basis, espresso contains approximately three times the caffeine content as regular brewed coffee (50 mg per fluid ounce of espresso versus 14-22 mg per ounce for coffee). But measured on a per-serving basis, a strict, one-fluid ounce shot of espresso (with 50 mg of caffeine) has about half the caffeine of a standard six-fluid ounce cup of American-style coffee, which varies from 80 to 130 mg.