Choose the Right Malt
A high protein content in malt and dextrin enhances the durability of the beer head foam and also enriches the body of the beer.
However, excessive protein and dextrin can react with tannins (polyphenols) and affect the clarity of the beer.
The commonly used malt to enhance the beer head foam includes crystal malt (such as carapils, carafoam, caramel malt) and wheat malt. Additionally, dark malt (such as chocolate malt) contains more melanoids and Maillard reaction products, which also help enhance foam persistence.
Adjust the Wort Protein Rest Temperature
Since the maintenance of beer head foam is closely related to the protein content in the wort, processes that destroy these proteins will have a certain impact on foam stability.
The typical protein resting temperature is 49-54°C, which reduces proteins that cause turbidity during cold storage but also breaks down proteins that are beneficial for maintaining beer head foam. Therefore, for malt with good solubility, excessive protein rest is not necessary. It is only recommended to carry out protein rest when using more than 25% un-sprouted malt (barley flakes, wheat flakes, rye flakes, oatmeal).
For malt with good solubility (that has undergone complete malting), use a temperature range of 68-71°C to create sugar, avoiding protein inactivity to achieve a richer body and improve beer head foam retention.
The bitter substances in hops promote the formation of a network of bubbles, facilitating the formation of beer head foam.
These bitter substances also help to create “foam lace” in your beer. When the beer is poured, the foam is moist and fluffy. After a few minutes, the foam adheres to the glass wall, forming a white lace pattern.
The longer the fluffy foam is maintained, the better the lace remains on the glass. Generally, beer with a higher hop content has richer and longer-lasting bubbles, but be mindful of the beer’s bitterness.
Mix with Nitrogen
Many breweries fill beer with a mixture of nitrogen and carbon dioxide to achieve a richer, finer, and longer-lasting foam.
In addition to affecting foam, mixing nitrogen gives the beer a creamy and smooth taste while reducing bitterness.
The ratio of carbon dioxide to nitrogen in the mixture depends on the beer style. For low-carbonation stouts, a 25% carbon dioxide to 75% nitrogen ratio is recommended. Ales and lagers may require a higher carbon dioxide ratio, such as 60% carbon dioxide to 40% nitrogen.
If a low carbon dioxide ratio (25/75) is used, one cylinder can be used for two mixed gases. If the ratio is high, separate cylinders are required: one for nitrogen and one for carbon dioxide.
Choose the Right Glass
The choice of beer glass has a significant impact on the beer. The right glass enhances not only the foam head but also the aroma and overall flavor experience.
In general, a slender, narrow-mouthed glass reduces the exposed area of foamed beer to air and restricts the escape of carbon dioxide, thus improving foam longevity. On the contrary, a wide mouth allows carbon dioxide to escape more rapidly.
Representative slender beer glasses are the Pilsner glass for drinking lagers and pilsners, and the wheat beer glass for drinking wheat beer.
Some beer glasses (such as Caris wine glasses) have small dents etched on the bottom to provide nucleation points for bubbles, allowing the beer to continuously produce bubbles.
*Note: Ensure the beer glass is clean and oil-free. Avoid inserting lemon slices into the glass as they can significantly disrupt the beer head foam.
Household soaps, including dish soap and laundry soap residues, can negatively affect the foam on the beer head. Thus, it is best to avoid using them to clean brewing equipment and beer glasses.
Propylene Glycol Alginate (PGA)
Because oily substances can greatly diminish beer foam, some breweries add PGA to beer to improve the stability of the head foam.
Foam is essentially formed by numerous small bubbles gathered in a small amount of liquid. PGA gathers on the surface of the bubbles, forming a protective layer that prevents grease from penetrating and destroying the bubbles.
Increasing the viscosity of beer can slow down the rate at which foam disappears. Since beer viscosity decreases as temperature decreases, low-temperature beer tends to have better foam stability.
However, note that carbon dioxide is more soluble at low temperatures. Therefore, beer served at low temperatures (such as very cold lagers) will produce less foam despite having the same carbon dioxide content.