I eat yogurt almost every morning for breakfast. It’s ideal for packing up and taking to work, or I can gussy it up at home with homemade granola and sliced fresh fruit. I go through at least one large container of plain Greek yogurt every single week. But when I open it up to make breakfast, there’s often a translucent white liquid amid the thick, creamy yogurt.
I never know what to do with it. Do I pour it out? Stir it back into the container?
This milky liquid is called whey, and over the past two months that I spent researching yogurt I learned all about what whey is and all of the delicious ways it can be used.
Sign up for the Well-Equipped Cook newsletter
Shop smarter with our ATK Reviews team's expert guides and recommendations.
What Is Whey?
There are two types of whey: Sweet whey and acid whey. Sweet whey, which contains lactose, is the liquid drained off in the making of rennet-coagulated cheeses, such as cheddar or Parmesan. It’s often sold to companies who turn it into products like whey protein powder.
The type of whey you’re much more likely to encounter is acid whey, which is the liquid that is drained from acid-coagulated cheese or from strained yogurts, such as Greek or Icelandic. It can also naturally separate a bit in big tubs of yogurt. It contains mostly water, lactic acid, and as many probiotics as the yogurt itself.
Greek and Icelandic yogurts are some of the most popular strained yogurts on the market. During the yogurt-making process for these types of yogurts, only one quarter of the milk used turns into yogurt and the rest is whey, which is about as acidic as orange juice. Large companies have a huge excess of whey, and some get rid of it by selling it to farmers to use in animal feed or even to utility companies to turn into methane, which in turn can produce electricity.
Should You Pour off the Whey?
If you notice liquid whey in your tub of yogurt, you can stir it right back in. It is perfectly tasty and nutritious, and it will separate whether your yogurt is brand new or a few days old. You can also just pour it out if you want, but it’s healthy and full of flavor, and pouring out a significant amount will make your yogurt more thick.
How Can You Use Whey?
If you do choose to pour the whey off, don’t pour it down the drain! Save it for other uses. In many cultures, such as in Iran, whey is a prized ingredient that is consumed by itself or in a myriad of other ways. Homa Dashtaki, owner of White Moustache Yogurt in Red Hook, Brooklyn, and author of Yogurt & Whey (2023), recommends using whey in a marinade for meat, as its thinner viscosity is even more effective at penetrating meat than thicker yogurt or buttermilk.
At the Persian restaurant Sofreh in Brooklyn, chef Nasim Alikhani makes the yogurt in-house and they are frequently swimming in excess whey. In Iranian cuisine, this whey is treasured. “We call it liquid gold,” said Alikhani. In Iran, she grew up just drinking the whey, as did Dashtaki, as it is hydrating and full of beneficial probiotics. When Alikhani has an abundance of whey, she will reduce it and “add a bit of cornstarch and freeze it in cubes and throw it in stocks or ash. I call it Persian umami.”