Espresso

Espresso is a coffee-brewing method of Italian origin, in which a small amount of nearly boiling water (about 90 °C or 190 °F) is forced under 9–10 bars (900–1,000 kPa; 130–150 psi) of pressure through finely-ground coffee beans. Espresso coffee can be made with a wide variety of coffee beans and roast degrees. Espresso is generally thicker than coffee brewed by other methods, with a viscosity of warm honey. This is due to the higher concentration of suspended and dissolved solids, and the crema on top.

Brewing
Espresso is made by forcing very hot water under high pressure through finely ground compacted coffee. Tamping down the coffee promotes the water's even penetration through the grounds. This process produces an almost syrupy beverage by extracting both solid and dissolved components. The crema is produced by emulsifying the oils in the ground coffee into a colloid, which does not occur in other brewing methods. There is no universal standard defining the process of extracting espresso. Generally, one uses an espresso machine to make espresso.

Espresso Roast
Espresso is both a coffee beverage and a brewing method. It is not a specific bean, bean blend, or roast level. Any bean or roasting level can be used to produce authentic espresso. For example, in southern Italy, a darker roast is generally preferred. Farther north, the trend moves toward slightly lighter roasts, while outside Italy a wide range is popular.

Shot Variables
The main variables in a shot of espresso are the "size" and "length". This terminology is standardized, but the precise sizes and proportions vary substantially. Cafés may have a standardized shot, such as "triple ristretto", only varying the number of shots in espresso-based drinks such as lattes, but not changing the extraction – changing between a double and a triple requires changing the filter basket size, while changing between ristretto, normale, and lungo may require changing the grind, which is less easily accommodated in a busy café.

Nutrition
Probably owing to the higher quantity of suspended solids—compared to typical coffee, which is absent of essential nutrients—espresso has significant levels of dietary mineral magnesium, the B vitamins niacin and riboflavin, and around 212 mg of caffeine per 100 grams of liquid brewed coffee (table).