Mystery of Swiss Cheese Holes

The distinctive holes in Swiss cheese, also known as 'eyes,' have puzzled cheese lovers for centuries. Contrary to popular belief, they aren't caused by mice nibbling at the cheese. But what actually causes these holes?

Propionibacterium freudenreichii, a bacterium used in the cheese-making process, is the main culprit. During fermentation, these bacteria produce carbon dioxide gas. This gas forms bubbles, which create the holes as the cheese solidifies.

Recent research revealed that microscopic hay particles in milk play a vital role. These particles provide nucleation sites where gas bubbles can form more easily, leading to the iconic holes in Swiss cheese.

The formation of holes affects the texture and flavor of Swiss cheese. The gas pockets make the cheese softer and contribute to its unique taste by altering the distribution of moisture and fat.

In the cheese industry, the size and number of holes are carefully controlled. Cheese with too few or too many holes can be deemed inferior. The perfect Swiss cheese has a balanced distribution of well-sized holes.

Swiss cheese holes persist even in zero gravity, as demonstrated in experiments aboard the International Space Station, proving the gas formation process is unaffected by gravity.