Whey left on the counter, still good to use?

How long can whey be left on the counter for? I realized the whey left over after making ricotta was left on the counter for 48 hours. It smells like buttermilk. Not pungent, just slightly sour. Is it still good to use? I can't seem to find anything about how long it could be left out and I'd love to use it in breads or something if I can.