Espresso is simply a unique method of brewing, nothing more. It is a child of modern technology that has been perfected over the entire course of the twentieth century. The coffee can be anything: light-roasted, dark-roasted, a blend, a single-origin, even pre-flavored (God forbid!). Those who believe that espresso must be made with dark-roast coffees have never appreciated North Italian espressos, where finer coffees are purchased and consumed.
Perhaps extra dark-roasted coffee is associated in the United States with espresso because the Italians who first made espresso in this country were mostly poor immigrants who could afford only lower quality coffee beans, including a lot of inferior Robusta coffees. Poorer quality coffees are traditionally roasted very darkly in Europe. Dark roasting makes poor-quality coffee more palatable by masking some of its undesirable flavors with a rich coating of bitterish carbonization. What is born of necessity ultimately becomes acquired taste. As one travels from Southern Italy to the traditionally more prosperous North the quality of the coffee improves, and the roasts progressively lighten up.
Quoted from Ernesto Illy’s definitive book on espresso (Espresso Coffee, Academic Press): Espresso is a brew obtained by percolation of hot water under pressure through a cake of roasted ground coffee, where the energy of the water pressure is spent within the cake.
A single espresso is a mere 25 to 30 ml, with a ristretto being 20 ml (brewed in the same amount of time) and a luongo at about 50 ml. Six-and-a-half to seven grams of very finely ground, heavily tamped coffee is typically used for theses doses. Water temperature should be around 194º F. Pressure should be around nine atmospheres. Brewing time should be between 20 to 30 seconds.
Espresso should be drunk immediately upon being made. Otherwise the crema (foam) shrivels away, and the seamlessness of the beverage’s structure tends to break down, especially those made with inferior beans. The crema should last at least two minutes. Not only does crema add a visual and textural delight to an espresso, it also seals in the aromatics of the dense beverage.
The finest espressos require no sugar; they are quite naturally sweet!
Espresso should always be enjoyed in porcelain, never paper! It is an instant, pure moment. Stand at the bar and imbibe in two or three sips what should be like an intense ray of dappled sunshine or the finest bonbon. Then enjoy what should be the very long and chocolaty aftertaste.
The espresso beverage is an emulsion of oil droplets, a suspension of minute solid particles, and a mist of gas bubbles, lending effervescence to the deeply extracted beverage for the first one to two minutes.
Espressos run the gamut from: astringent, robust, heavy, coarse and/or bitter to bitter-sweet, subtly complex, lively yet creamy, with long persistence of a smooth, even, sweet, aftertaste without any harshness or bitterness.
Pure espresso is very under-appreciated in the United States, primarily because of the prevalence of extremely bitter, dark-roasted offerings, compounded by the popularity of extremely sweet soft drinks and beyond-sweet artificial sweeteners, particularly with younger people.
Cappuccino is suffering a similar fate, often replaced by milky lattes, which cover extreme bitterness better, or transmogrified into 8-oz., 12-oz., or even 16-oz. paper cups.
A classic cappuccino emphasizes quality over quantity; it has elegant proportions of micro-foamed milk and espresso totaling a mere five liquid ounces. There should be no bitterness, regardless of the lack of sugar. Cappuccino is a sensuous drink and should always be drunk from a porcelain cup.