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Hey, Squeaks! How about we have a little snack?

I’ve got something in mind that I think you’ll really like! This snack comes from a cow, but it’s not milk! Though it’s actually something that’s made from milk. [Squeaks squeaks] That’s true, we’ve made butter from milk before … but it’s not that, either. [Squeaks squeaks!] Yep!

It’s cheese! This is Swiss cheese! It’s called that because it was originally made in Switzerland, which is a country in Europe.

But now Swiss cheese is made all over the world, including here in the United States. You might notice something about this cheese that you don’t normally see in other foods: it has all those holes! Most other types of cheese don’t have holes in them, so Swiss cheese is pretty special.

Cheese experts actually call these holes “eyes,” which is kind of funny because they’re totally different from our eyes. So why does Swiss cheese have “eyes”? Is it because Squeaks has been nibbling at it? [Squeaks squeaks].

I’m just kidding, Squeaks! The holes in Swiss cheese aren’t made by animals! Let’s get to the HOLE story!

Get it, Squeaks? Hole? [Squeaks laughs]. The really cool thing about cheese is that it’s actually made with germs!

Yeah, that’s right: germs! Another word that scientists use to talk about these germs is bacteria, and there are some kinds of bacteria that can make us sick. But the bacteria in cheese is safe!

Cheesemakers add different types of bacteria to milk, along with some other stuff, to make different types of cheeses. And there are so many! Maybe you’re a fan of mozzarella?

That’s the kind you can usually find on pizza. And I know we’re big fans of pizza! Or maybe you like cheddar cheese?

Cheddar makes an excellent grilled cheese sandwich! And there are soooo many more! Anyway, back to Swiss!

I know you’ve been waiting to find out the HOLE story about those holes! [Squeaks squeaks]. I guess that was a CHEESY joke! The bacteria that cheesemakers add to Swiss cheese eat some of the cheese, but that’s not exactly what causes the holes.

When the bacteria eat the milk, they cause a reaction. A reaction is when two things mix together, and sometimes they create a third thing! In this case, when the bacteria eat the milk, they create … bubbles!

Those bubbles take up room in the cheese, and when they eventually pop, we’re left with holes. Totally weird, right? But here’s the thing: The Swiss cheese we eat today doesn’t have as many holes in it as it used to, and sometimes it ends up not having any holes at all!

So what’s different now about the way we make Swiss cheese now? We’re still using the same bacteria. Scientists think there are less holes these days because the bacteria isn’t doing ALL the work in making them.

Little bits of hay might be helping the process along! So what’s hay? And why is it in cheese?

Hay is something you’ll find on a lot of farms. It’s dried out grass that’s used to feed animals, like cows and sheep and other animals that make milk! So little tiny bits of hay might accidentally get into the buckets used for collecting milk.

Then, scientists think the bubbles from the bacteria form around those little bits of hay. So the hay is important for creating the bubbles that make the holes when they pop. Now that cheesemakers have more modern ways of making cheese, hay doesn’t get in the buckets anymore.

So that might be why there aren’t so many holes anymore, even though the bacteria is the same. And there you have it! The mystery is solved: hay and bacteria work together as a team to make bubbles that leave holes when they pop!

So the holes definitely aren’t made by mice or rats or robot rats eating the cheese! Thanks for joining us! If you want to keep learning and exploring with Squeaks and me, hit the subscribe button, and don’t forget to check us out on the YouTube Kids app.

We’ll see you next time, here at the Fort! ♩.