Why do Cheese Curds Squeak?

Before we wrap up our two week look at the science of the dairy state, I thought it would be fun to share one last dairy fact that I’ve learned about during my time as a science writer in Wisconsin. I hope you enjoy and be sure to check back next week as we discuss the latest in science education.

 Why do Cheese Curds Squeak?

The Curd:

As we discussed last week, cheese curds are formed during the final stages of the cheesemaking process. While cheese curds can go on to become blocks of Cheddar, Brick or another cheese, some cheesemakers choose to stop the process a little early and allow customers to savor the warm, squeaky joy of a fresh cheese curd.

 Here in Wisconsin, fresh cheese curds are an iconic treat. In fact, there are stories of people lining up outside of cheese plants in the morning when the fresh curds are made just to get a bag of this squeaky, salty snack. After biting into this unique treat, one of the first questions many people ask is why does the cheese squeak when I bite down on it? In fact, as a science writer in the food world, this is one of the most common questions I see come through my email. So, here's a quick look at the science behind the squeak. Enjoy!

The Squeak:

At a basic level, the squeak in cheese is caused by the compression of protein networks. In other words, when you bite down, the strong protein networks in the cheese resist your teeth and then rebound as you bite through resulting in a squeak. Of course, it’s a bit more complicated than that so here’s a basic breakdown. 

Cheese contains a protein called casein which is often called the building block of cheese. These casein proteins are bonded together by calcium phosphate molecules which help to give cheese its structure and strength. In a fresh cheese curd the bond between the calcium and the casein is very tight which is why a fresh cheese curd has that strong resistance and quintessential squeak. Over time, however, the calcium bonds are dissolved by the acid in the cheese, thanks to a process known as proteolysis.

While the name sounds complicated, it is essentially a term used to describe the breakdown of proteins. In an aged cheese proteolysis is good because the breakdown of proteins aids in flavor development, but in a cheese curd it is bad as the weakened protein bonds will no longer resist teeth and create that chewy, squeaky feeling that is so loved by cheese curd connoisseurs. Proteolysis happens quickly in cheese curds. In fact, a typical cheese curd will lose its squeak within two to three days, which means that only those individuals living near cheese plants can enjoy this tasty treat.

Researchers at the Center for Dairy Research have been working to study the science of the squeak, however, and recently discovered that proteolysis can be slowed by refrigerating or freezing the curd.  This is exciting because slowing proteolysis in the curd would allow cheesemakers to transport the curd, thereby sharing  this iconic food with those outside of the state.

So there you have it, the science of the squeak.

Still hungry for more? Be sure to check out the Dairy Pipeline, Vol. 28. #3 (available later this week at https://www.cdr.wisc.edu/pipeline) to learn more about the  research discussed above.


And, be sure to check back Friday as we learn about a local elementary school who has taken science education to the next level.