The best espresso is characterized by foam (crema) of a light brown color (with a reddish shade), with light stripes evenly distributed in the foam.

Espresso foam can be very dense, homogeneous, and steady, with very few bubbles. The foam should have neither big bubbles or white spots (allocation of fractions of heavy caffeine), and should not have ruptures in the surface of the foam through which the coffee underneath can be seen.

A gray shade means that more Robusta beans than recommended have been used. A white shade, on the other hand, signifies an insufficient extraction during the brewing (quantity of coffee ground less than 6 grams, coarse grinding, insufficient pressure in the device, a water temperature less than 88 C °, water pressure below 9 atmospheres, time of extraction less than 20 seconds)

Black tops in crema and white bubbles breaking the foam signify too much extraction during the brewing (The quantity of coffee being more than 12 grams, fine grinding, high pressure in the device, water temperature more than 92 Degrees Celsius, water pressure above 9 atmospheres, extraction time more than 28 seconds). If the extraction is either insufficient or excessive, you’ll end up with practically no crema, due to the use of blends with limited quantities of oils and high-molecular glucids, or old ground coffee. The same also holds true for crema that disappears quickly.

Used coffee tablet:

Inspect the look and structure.

If the espresso has been brewed correctly, the coffee tablet:

* will be slightly damp

* keeps a structure — as plasticine

* The portafilter keeps its shape, and doesn’t collapse.

* Breaks, but does not crumble.

Correcting mistakes:

A dry and crumbling tablet means the grinding is too coarse, the amount of coffee too large, or the tamping too strong.

A tablet that’s “spreading” means that the grinding is too fine, the amount of coffee is too small, or the tamping is too weak.

Cremá (foam):

Inspect the: color, density, features of structure and stability.

Cremá is formed in during the extraction: proteins, fats and high-molecular sugar turn in emulsion; allocated gases, entering with emulsion interaction, make foam. The characteristic color is due to the caramelization of sugars and oxidation of phenols.

If the espresso has been brewed correctly, the crema will:

* Have a reddish-brown color (colors of a nutshell of a filbert);

* Have a thickness of over 2 mm;

* Be continuous, without any holes or ruptures

* Not have any large bubbles

* Be steady, and keep for over 2-3 minutes

* Be “live”, it’s restored after drink hashing

* Have dark brown strips or specks (like a tiger or a leopard’s skin).

Correcting mistakes:

A light brown color or small density of foam is due to insufficient extraction. Usually it’s for the following reasons: The grinding is too coarse, the tamping is insufficient, or the temperature or pressure is below normal.

A dark brown color and appreciable bubbles is a sign of excessive extraction. The grinding was too fine, the tamping temperature was too high, or the pressure was above normal.

A dark color with shades of gray or an earthy color is a sign of a considerable quantity of robusta coffee in an espresso blend.

A non-uniform friable foam means uneven tamping.

Aroma:

Inspect: both positive and negative characteristics.

Good aromas would be roasted, fruit, or flower. Examples of bad ones include: smoky, prorancid, grassy, straw, or rotten.

Taste:

Inspect: both positive and negative characteristics.

Good tastes include: sourish, wine, citron, chocolate, pleasantly bittered, flower, and balanced.

Bad tastes include: astringent, earthen, mealy, wooden, sour, medicine-y, and pith.

Poor smells and the flavoring characteristics shown in espresso can be the result of both the use of poor-quality beans and a consequence of unfair care of a coffee grinder and espresso machine.