Why do cheeses have holes?

Have you ever asked yourself why and how cheeses get their holes?

The origin of a widespread image in which an adorable mouse is peeking through big holes in cheese can probably be traced to the question often asked by children: “Why do cheeses have holes?” When we asked this question as children, the parents’ explanation that mice are “guilty” of that usually satisfied our curiosity, but the real reasons for the formation of cheese holes can be found elsewhere.

Cheesemaking is a connection of different biological processes that take place in milk and later in cheese.

During the cheesemaking process, we can trigger them either by adding natural cultures and rennet or by changing the environment (temperature and humidity).

As a natural ingredient, milk is home to numerous microorganisms and bacteria – the good ones, of course – that also have a role in the process of cheesemaking. Some of them turn lactose into lactic acid during a process called fermentation, while others influence the taste and texture of cheese.

Most of the microorganisms found in milk get there through animals’ fodder.

One such example are propionibacteria. During the ripening process, the propionibacteria “eat” dairy proteins and produce gases – the latter contribute to the formation of cheese holes. This process normally takes place in warm ripening cellars, as propionibacteria are not active at lower temperatures. At the same time, the temperature shouldn’t be too high, as propionibacteria don’t like that either.

The size, number and position of cheese holes strongly depend on the amount of propionibacteria in milk. As this amount differs depending on the season and the weather, homemade cheeses are never exactly the same, but keep changing throughout the year.

As we can see, cheeses get their typical holes due to slightly more complicated factors than just hungry mice from the yard.