Swiss cheese has holes because of carbon dioxide bubbles that form in the cheese. That’s the short answer.

But if you really want to know more about the science behind the Swiss, we have you covered.

What Causes The Holes in Swiss Cheese?

The holes in Swiss cheese form thanks to a bacterial culture called Propionibacteria, or Props. These bacteria are naturally found in hay, grasses, and soil, and can be present in raw milk. Pasteurization kills most bacteria, so cheesemakers often add Props back to ensure the characteristic bubbles develop.

As the bacteria ferment the cheese, they produce carbon dioxide, which creates the holes and contributes to the cheese’s nutty flavor.

How Is Swiss Cheese Made?

After production and brining, Swiss cheese is aged in warm rooms. This environment allows the bacteria to release carbon dioxide while keeping the cheese’s texture consistent. This process explains why Swiss cheese has holes in it and shapes its distinctive taste.

What Are The Holes in Swiss Cheese Called?

In Swiss production, these openings are referred to as “eyes.” Their number, size, and distribution are carefully monitored and regulated by the USDA. Properly formed eyes are a mark of quality.

Types of Swiss Cheese

In the U.S., we call it “Swiss” cheese, while in Switzerland, it’s known as Emmental. Varieties of swiss such as Baby Swiss and Jarlsburg are all forms of Emmental, differing in moisture, fat content, and sometimes additional bacteria. These cheeses are all examples of cheese with holes in it, though the appearance of holes can vary.

Fun Facts About The Holes In Cheese

Other cheeses can develop holes too, often due to different bacteria or natural fermentation conditions. Gouda, for example, can have small, pea-sized openings, and raw milk cheeses occasionally form them as well.

Swiss cheese without holes is called “blind” but still tastes the same. Hole sizes range from a dime to a quarter, and cheesemakers carefully manage these details to meet quality standards.