Optically: On sight, Italian Espresso has a hazelnut-coloured froth, verging on dark brown with tawny hinges. During the extraction we talk about tiger striping: It is formed by the contrast of darker and lighter crema in the espresso stream; ideally it begins early during the extraction and is sustained till the end. Directly after the extraction is finished, we talk about mottling: The in-cup confirmation of a good espresso coffee extraction: Also called tricolore, it comprises the darker brown layer on the bottom, followed upwards by a reddish-brown layer in the middle and on the top the crema. This crema on top needs to have a very fine texture, which means that its mesh is tight; large or small bubbles are absent in a good crema.
Flavor: The nose reveals an intensive scent with hints of flowers, fruits, toasted bread, hazelnut and chocolate. All of these sensations are felt also after swallowing the coffee in the long lasting aroma that remains for several seconds, if it is a high end espresso roast even for minutes, we call it the lingering aftertaste. Its taste is round, substantial and smooth. Hints of sweet, sour, bitter (not acids) are well balanced and neither one prevails over the other. Acids and astringency are absent or barely perceptible.
Technically: A jet or shower of hot water at 190°-194°F passes under a pressure profile (seven - nine - six atmospheres) through a seven-gram (.25 oz) cake-like layer of tampered espresso ground coffee. Done right, the result is a concentrate of not more than 1 oz of straight espresso within 20 – 25 seconds.