Bowl of white yogurt and spoon
What Is That Watery Stuff On Top Of Yogurt (And Do You Need To Discard It)?
By Julia Mullaney
Whether you’re eating Greek yogurt for its fewer calories or traditional yogurt for its higher calcium content, yogurt is an excellent and versatile snack with just one confusing quality: the unappealing liquid pooled at the top. Fortunately, this watery substance can simply be mixed into the yogurt for a nutritional boost.
There’s a natural separation between the curds and whey when yogurt is made, and once it’s packaged and left sitting for a while, whey naturally separates, creating a watery substance on top of the curds. According to Amanda Sauceda, RDN, “There‘s tons of nutritional value in whey...It’s rich in protein,” so while you may prefer to dump it out, there is only added value to mixing it in. 
The natural separation is no indication that your yogurt is expired. To determine if your yogurt has actually gone bad, check for a sour scent or lumpy texture, and throw it away immediately if you see mold with a blue-green color or a gray-white color.