Head Retention

An important characteristic in beers is the ability of the beer to retain a nice foamy head for a long period of time. Commercial brewers go to great lengths to improve head retention by a variety of additives. However homebrewers also have access to quite a few ingredients and additives that can help your foam last until the last drop.

Foam is the result of CO2 bubbles rising through the beer. These bubbles attach themselves to substances in the beer and form a skin around the bubble. Obviously the more CO2, the more bubbles, but the goal of the brewer is not bubbles but stability of the head. Head stability depends on the presence of substances with low surface tension in the beer which can form stable elastic bubbles. The two primary contributors to head retention are certain high molecular weight proteins and isohumulones (alpha acids from hops). Therefore beers with more proteins that are highly hopped will have a higher head retention.

Methods for Improving Head Retention

We will explore the following possibilities:

• The use of body and head enhancing |malts such as crystal, wheat, or carafoam
• The altering of the mash schedule to enhance head retaining proteins
• The use of heading agents - additives that enhance head retention
• Limiting the use of household soaps on drinking glasses and homebrew equipment
• The use of a nitrogen and CO2 mix for carbonation and serving

Head Enhancing Malts

The inclusion of proteins and dextrines enhance the body and head retention of finished beer. Unfortunately when used to excess, proteins and dextrines can interact with tannins and reduce clarity and promote cloudiness, so a proper balance must be struck. Crystal malts to include the light Carapils and Carafoam, and caramel malts. These are the most common body and foam enhancing additives that enhance head retention primarily by adding dextrines and other complex proteins. The overuse of such malts can result in proteins reacting with tannins to create a chill haze. Similarly, other grains high in protein such as flaked barley and wheat can be used to enhance head retention, though again at the cost of clarity.

Mashing Schedule

Since head retention depends on the level of high molecular weight proteins, any step in the mash that breaks down proteins is undesirable. For example, a protein rest in the 50-60 C (122-140 F) range would not be desirable. To improve head retention you would generally favor a full bodied, higher temperature mash, with main conversion in the 158 F (70 C) range, and avoid intermediate protein rests.