It’s a Friday and you just got off work, you pour yourself a beer and at the top of your glass is a thick, creamy foam-like layer that lasts, typically you go about drinking your beer, but today we’re going to make you wonder, what is that foam and why is it so desirable?
The foam that rests on top of the beer after it has been served is known as the beers head. Retention is the word used to describe how long the beer head lasts in your glass. The head on a beer exhibits aroma attributes that are not found after the head has died down, so it is for this reason, as well as aesthetic and stylistic reasons, that a beer with a good long-lasting head is desirable. Now that it has been confirmed why it is desired, we’re going to explain all the ways brew masters use to achieve the perfect long lasting head of foam.
Beer foam forms as the result of Carbon Dioxide bubbles rising up through the beer and attaching to other substances in the beer, producing a skin-like layer around the bubble. The more Carbon Dioxide in a beer, the more bubbles there are, however, the goal is not necessarily the amount of bubbles, but the stability of the head they form.
Head stability or retention is dependent on the presence of substances in the beer with low surface tension, resulting in the formation of bubbles characterized as stable and elastic. The main contributors for improving head retention are particular high molecular weight proteins and isohumulones. Both of these components are found in ingredients already used to make craft beer.
Proteins and dextrins are often derived from malts. Crystal malts such as Carapils, Carafoam, and Caramel malts, as well as Dark malts are believed to help improve head retention because of their high level of mellanoidins, which are protein polymers that occur upon the combination of sugars and amino acids. On top of these, wheat malts and flaked barely increase head retention also.
Isohumulones on the other hand are alpha acids produced by hops. Alpha acids are the primary bittering agent in hops, therefore, highly hopped beers have a better head retention.
Since head and retention are such important characteristics in beers, commercial brewers go to great lengths to improve it aside from adding specific malts and extra hops. Other factors brewers adjust are the mashing schedule, the addition of heading agents, the beer serving temperature, and the glassware the beer is served in.
Temperature plays a big role in beer head and retention as well. Viscosity or thickness increases as temperature decreases, therefore, the cooler a beer is the better the stability of the foam is.
The glassware in which the beer is served is also a largely important concept. The shape of a serving glass plays a huge role with the beer head, but you must choose the right one. Tall narrow beer glasses like Pilsner glasses are the best option for head formation and retention. It is also imperative that the glassware the beer is being served in is completely clean.
Just as additions are important for a beer head and its retention, it is important to avoid certain substances as well. Low protein adjuncts such as corn, rice, and sugar can decrease or limit heads retention abilities, making it best to avoid including them in beer recipes if the end goal is a strong head. Avoiding fats and oils is also imperative to maintain a beers head retention.
Of course, lots of beer foam and a significant head are not everybody’s favorite, so make sure you know if the beer you purchase fits your head preference before ordering it. If you aren't sure then our beer of the month club is a good way to try out different types of beers. Cheers!