Greek yogurt might have gifted us the feel-good story of the week, but its meteoric rise in popularity has a downside: acid whey. That’s the tangy, watery liquid that’s drained from curdled milk (and fresh cheeses like ricotta) to make the resulting yogurt so creamy. The less whey, the creamier the yogurt. In fact, because so much of the water content is strained out, it takes about 4 pounds of milk to make 1 pound of Greek-style yogurt.

The whey that’s a byproduct of yogurt is acidic—it has a pH similar to tomatoes or wine. The making of hard cheeses (think cheddar or Gruyère) also produces whey, but that whey is sweeter and contains more protein, so it can be turned into the whey protein you find in energy bars, for example. Acidic whey is mostly water, with some sugar, minerals, beneficial bacteria, and a little bit of protein.

The question of what to do with acid whey has become more and more pressing as Greek yogurt production has become big business. Scientists at Cornell University, the USDA, and Jones Laffin, a food industry group, are all on the case. (Requests for comment from scientists at Cornell and Jones Laffin were not returned by press time.) You can’t simply pour acid whey down the drain because if it gets into waterways, it causes a bacteria overgrowth that kills fish. Some large Greek yogurt producers give the acid whey to farmers for fertilizer and animal feed—in fact, the companies pay the farmers to take the whey off their hands. The complication is that each farmer is only allowed to take a little bit, a regulation designed to prevent the whey getting into runoff and ending up in the water supply. So yogurt companies have to truck the whey to multiple farmers hours away to get rid of it all.

The thing is, acid whey is useful, wholesome, and tasty—if the yogurt you buy has a bit of watery liquid at the top, that’s the whey. Simply stir it in. It has the same probiotics that yogurt does and it’s a good source of calcium. Acid whey can be refreshing as a cold drink, or useful as a brine or marinade. In fact, Homa Dashtaki, the founder of The White Mustache yogurt markets her whey as “probiotic tonic.” Chefs around the country are using acid whey to brine poultry, to flavor grits, and to make cocktails. At Vinland, in Portland, Maine, chef David Levi uses whey to season dishes instead of lemon juice.

Those solutions work on a small-batch level, but no one has yet figured out what to profitably do with the massive quantities of acid whey produced by, say, Chobani or Fage. However, given how much money is on the line, it’s likely that someone will figure out how to turn acid whey into gold soon: Last year, General Mills filed for an international patent on a method to turn whey into probiotics.

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