system
Given the following post, respond as if you're commenting on Reddit:
human
Why (and how) do the cheese curds used in poutine squeak when eaten?

The best poutine in Québec is produced with fresh salted cheese curds, which produce a distinctive squeaking sound when chewed (to the extent where it is often referred to as "squeaky cheese"). What properties of this cheese make it so?
gpt
Fresh cheese curds have more elasticity than stale ones. As the curd material rubs against your teeth, it vibrates due to that elasticity, making the squeak. It should be noted that "fresh" in the parlance of cheese curds is usually considered to be 12 or fewer hours old, though some retain their squeak for a day or two. 

The elastic squeak is why refrigerating cheese curds kills the squeak even if they're fresh - the cooler temperature reduces the tendency to vibrate. And that's why newcomers to the upper-midwest USA are often surprised to see bags of cheese curds in grocery stores sitting out on a table instead of a refrigerated case - the locals demand that squeak.