Why Does Swiss Cheese Have Holes?

(A Magical Look Inside Every Cheesy Bubble)

If you've ever sliced into Swiss cheese and wondered, “What are these holes doing here?” — you're not alone. These mysterious bubbles, often called "eyes," aren’t just for decoration. They're the result of a delicious scientific process that makes Swiss cheese so unique.

Let’s uncover the secret behind the holes in Swiss cheese.

1: It Starts With Three Friendly Bacteria

Swiss cheese begins with milk and three special kinds of bacteria:

• Lactobacillus

• Streptococcus

• Propionibacterium freudenreichii

These helpful microbes begin eating the lactic acid in the cheese as it starts to ferment.

2: Gas Bubbles Form (And That’s a Good Thing!)

As Propionibacterium eats lactic acid, it releases carbon dioxide gas — just like tiny burps inside the cheese!
This gas tries to escape, but the cheese is solidifying. Instead of bursting out, the bubbles get trapped inside.

These trapped bubbles form the famous holes — or "eyes" — in the cheese.

3: The Cheese Matures in a Magical Cave

Now the cheese wheels are stored in a cool, quiet room (much like a Ghibli-style aging cave). Here, they sit for weeks or even months, giving time for the bubbles to grow and the flavor to develop.

The longer the cheese ages, the bigger and more flavorful the holes become.

4: Each Slice Tells a Story

When the cheese is finally sliced, those beautiful holes show off the journey the cheese took — from milk to microbe to masterpiece.

Fun Fact:

Not all Swiss cheese has holes! Some are made without the gas-producing bacteria. And modern cheesemakers now understand that even tiny flecks of hay dust in milk can affect hole formation — just like a magical ingredient from nature.

In Conclusion

The holes in Swiss cheese aren’t mistakes — they’re a natural, flavorful part of the cheese-making magic.
Thanks to hardworking bacteria and patient aging, every slice of Swiss is a bubbly tribute to craftsmanship and nature’s quiet chemistry.