Antifoam in Brewing | Part 1

A good foam collar is an attribute of quality in a glass of beer; however, in some steps of the brewing process, could be advantageous to avoid foaming. Today, we will understand the life and death of the foam and the importance in the brewing process. I hope you enjoy the reading! Before starting, subscribe to this newsletter to be aware of any new content!

Foaming may be an issue in two processes in brewing: during boiling (hot side) and fermentation (cold side). The excess foaming results in difficulties in cleaning (in both processes), because of the organic matter that would be stuck in the vessel’s wall.

In addition to that, foaming may denature or destabilize beer foaming components, which leads to a worse foam formation in the final product (when we indeed want it). Loses of product and hop-bittering compounds could also be a result of this excessive formation of foam during brewing.

But we didn’t mention the worst problem of foaming yet: the large headspace requirement. In boiling, if the foam level reaches the venting system, the chimney cap will be turned into a fountain, literally. Hence, the kettle vessel is designed to never allow it!

In the cellar, the impact is even greater. Around 25% of the volume of the fermentation tank has to be reserved as headspace, or you may think of it as the space that will have foam. With all of this in mind, you can realize why some brewers add antifoaming agents to their worts/beers.

The Life of the Foam

Before talking about how to avoid/destroy the foam, we have to understand what it is. Long story short, foam is a matrix of bubbles. The interior of the bubble is gas (CO2 in brewing’s case), and the shell (or lamellae) is made of proteins. This bubble interacts with each other’s due to Van der Waals force.

Another important topic to foam is bubble stability, which depends on the balance of the superficial tension and the LaPlace pressure (difference between internal and external pressure).

This factor is strongly associated with the size of the bubble, where a smaller one has more stability. If you want to read more about foam formation, I recommend this article. It is focused on the foam in the final product; however, the science behind is the same.

The Death of the Foam

We may say that there are three ways for the foam to die: drainage, rupture, and coalescence.

The drainage is a slow and natural process. The water inside the lamellae is a pull-down because of the gravitational force; nevertheless, the adhesion due to capillary force makes the water to be redistributed (kind of resisting gravity). With time, the lamellae will become thinner, reducing the Laplace pressure and eventually breaking.

The rupture is when the lamellae separate two or more bubbles, or one bubble and the headspace, destroying the bubble. This may occur because of drainage or even due to a lack of stabilizer agents, such as hops compounds and proteins (hordeins and LPT1). The coalescence is when there is a local rupture in lamellae, and two bubbles become one bigger. The increase in size also destabilizes the bubble (Laplace pressure) and will lead to the rupture of the bubble.

In the next article, we will talk about the types of commercial antifoam and their mechanisms. Thank you for reading!