Why does yeast foam?

Yeast foams because it produces carbon dioxide gas as a byproduct of fermentation. When yeast is added to a sugary solution, it begins to convert the sugar into ethanol and carbon dioxide. The carbon dioxide gas bubbles up to the surface and forms a foam. This process is what gives bread its rise and beer its fizz.

The amount of foam that yeast produces depends on several factors, including the type of yeast, the sugar content of the solution, and the temperature. Some yeasts produce more foam than others, and some sugars are more fermentable than others. The ideal temperature for yeast fermentation is between 70 and 80 degrees Fahrenheit.

Yeast foam can be a nuisance when it comes to brewing beer, but it is also an important part of the brewing process. The foam helps to protect the beer from oxygen, which can cause the beer to spoil. It also helps to give the beer its characteristic flavor and aroma.