Science Byte

Why do cheese curds squeak? And why do they lose their squeak?

This post was inspired by “Cheese Curds: A Wisconsin Icon” in the CDR Dairy Pipeline. There is a link at the end of this post.

While most folks associate squeakiness with cheese curds, it can be found in other cheeses. Finnish Bread Cheese, fresh Halloumi, and young LMPS mozzarella can all squeak in some cases. You may notice a unifying trend between these cheeses—they’re young and low in acid (higher pH). Your teeth exert pressure to bite through the cheese curd, and that motion generates squeak from the friction against the cheese protein structure. Read on to learn what makes that structure unique.


Making cheddar cheese curds

There are two main things at play that determine if, and to what extent, cheese curds will squeak: intact protein structure and bound calcium. The intact protein structure is mostly a function of age. Young cheese has intact protein. As cheese gets older protein breakdown occurs (called proteolysis). Bound calcium is a function of pH or acid development. Higher pH (lower acid) cheeses have more bound calcium. Lower pH (higher acid) will lead to less bound calcium. Acid dissolves calcium from the cheese structure. We’ve covered this concept to death at this point. (See here and here) Overall, the cheese curd needs to a have a sturdy, intact, and highly-calcium-crosslinked structure to squeak.

Why do fresh cheese curds lose their squeak after a couple days? In the days following the birth of a cheese curd, the starter culture continues consuming lactose, transforming it into lactic acid. Eventually enough acid is produced and enough calcium is dissolved that the squeak disappears due to the weakened cheese structure.

Fresh Old Heated

Click the buttons above to see how the structure of cheese curds change. The blue blobs are casein strands and the yellow shapes represent calcium.

Common lore says one can microwave cheese curds briefly to retain the squeak temporarily. That little burst of heat is thought to constrict the protein structure briefly.* But be warned—heating the cheese curds too much will just melt them, and especially aged curds can’t get their squeak back. The best way to preserve the squeak is to freeze them.

*This exact mechanism still remains unknown, but hydrophobic interactions within the casein matrix probably play a crucial role.

For a fuller understanding of squeak and its subsequent loss, please check out the article titled “Cheese Curds: A Wisconsin Icon” in the CDR Dairy Pipeline, 2016, Volume 28, Number 3 (page 4-5).


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