Why does sour cream get watery?

From topping off a steaming baked potato to adding a little tang to a baking recipe, sour cream is just the thing if you need a little bit of tartness in your food. It can be a little unpleasant, however, when you reach into the fridge for some sour cream, pull the lid back, and see some water on the surface — and really, it's not even water, actually, but a watery, milky looking liquid. It certainly wasn't there when you first opened your sour cream a couple of days ago, so what's it doing there now — and should you be concerned?

Don't worry, this milky liquid floating on top of your sour cream is totally normal, but there are a few things you should know about it. 

What's up with whey?

Sour cream is made by adding bacteria to pasteurized cream and allowing it to incubate until the cream's lactic acid produces the desired thickness and the sour flavor that it's known for (via California Dairy). A very similar process is used to make yogurt, which means that liquid can pop up on top of that dairy product, too. The watery liquid, while it looks weird, is actually known in dairy lingo as "whey." 

Whey is nothing to be scared of, and it's actually good for you because it's rich in calcium and protein (via Today). What happens is that whey is naturally present in milk, but when the milk is turned into sour cream or yogurt, that whey is held in suspension within the milk's cell walls. Simply dipping a chip or spoon into the cream breaks those cell walls, which allows the whey leak out. 

The solution? Just stir it back into your sour cream and you're good to go — but first, check to make sure your sour cream hasn't started to go bad.

Check it to see if your sour cream gone bad

So some liquid on top of your sour cream is totally normal, but you should still check to make sure that the sour cream hasn't actually gone bad. Pay attention to the expiration date printed on the container, but use your nose too. A tangy odor is what you want, but a pungent odor that reminds you of sour milk is not a good sign (via Leaf). The whey should also look watery, but if it's chunky, that could also be a sign that it's curdled and should get chucked into the garbage. 

Sour cream is supposed to stay fresh for up to two weeks, but it's best to use your own judgment and decide if it's fit for your food — or better tossed in the trash.