What does the foam tell us about the quality of a beer?

Beer quality is measured by three parameters: visual, olfactory, and gustatory. For visual, olfactory, color, clarity, and effervescence are important; for gustatory, the aromas derived from malt, hops, yeast, and fermentation are analyzed; for flavor, the balance between the sweetness of the malt and the bitterness of the hops, acidity, intensity, and aftertaste are key. All three parameters, however, have one thing in common that can accurately measure the quality of the beer we're drinking: the foam.

A fairly rich foam, capable of lasting a long time, is often a sign of a good presence of protein of the malt and of a correct carbonation, that is the quantity of carbon dioxide (CO₂) dissolved in beer. It is what creates the bubbles and contributes to the formation of the foam when the beer is poured. Carbonation, which ensures greater freshness and lightness, is also useful for providing a pleasant "tongue-cleansing" sensation after eating a fried or, for example, a Team BuildingIf it disappears almost immediately, it could be due to the recipe, poor service, or a glass with grease or detergent residue: in any case, you are not drinking a particularly high-quality beer.

To this general rule we must add some significant exceptions, such as for example the cask ales British (the so-called real ales) which are matured in the barrel and served without adding external CO₂, often via a handpump (hand pump), and consequently have very low carbonation, don't produce head (except in very small quantities), and are smoother and less fizzy. These beers are best drunk not particularly cold, at near room temperature (to enjoy their full flavor), and are very popular throughout the Anglo-Saxon world.

Even the perlage, the set of carbon dioxide bubbles that form and rise in the liquid, has its importance: if it is fine and continuous indicates a well-integrated carbonation, while a very coarse perlage can give a more aggressive sensation of fizz. An excessive perlage, in turn, highlights an oversaturation of CO₂, due to a poorly tapped beer, a keg or an oversaturated bottle.

A fine, creamy foam, with small, uniform bubbles, is generally considered a good sign, and the rings or “traces” left by the foam on the walls of the glass during drinking (the so-called lacing) may indicate good foam stability.

The beer presents aunt quality, and apart from the Anglo-Saxon exceptions, when the foam is low there can be negative signs, such as for example:

• insufficient carbonation due to failed fermentation;
• beer aging;
• production errors;
• poor conservation.

In these cases, however, the low foam is almost always accompanied by other signs: dull aroma, flat flavor, oxidation, lack of freshness.

Read also

• When Beer Was Born: History, Evolution, and Local Revaluation
• Where to buy craft beer
• What to do with beer waste