Now I Know: Yogurt Water is Whey

Breakfast most days is half-a-cup of nonfat plain yogurt mixed with a quarter-cup of granola chased with half-a-pot of coffee.

I buy Trader Joe’s French Village Nonfat Yogurt in the 32 ounce tub* (good enough for fourth place!). About a day after opening a fresh tub, a thin milky liquid rises to the top. It’s yellowish and unappetizing. Every morning I pour it down the drain before scooping out breakfast.

Not anymore. That stuff is whey.

Whey is a dairy byproduct usually associated with the making of cheese or butter. Old time cheese makers added rennet, a soup of enzymes found in mammalian stomachs that aids in milk digestion, or an edible acid such as lemon juice or vinegar to milk to begin the process. The additives cause the milk to curdle, or separate into solids (“curds”) and liquid (“whey”). Today cheese makers use a genetically engineered rennet substitute to induce curdling.

Whey is filled with protein and amino acids. It is used to fortify all sorts of food products, from Oreo Cookies to KFC’s coleslaw. It is fed to farm animals. It is powdered and poured into bulging plastic bottles with label designs that promise potency, power and vitality. Whey protein is popular with bodybuilders.

Yogurt is produced by introducing bacteria to heated milk. As the bacteria consume sugar (lactose), they release lactic acid, which causes the curds and whey to separate. When the right pH level and consistency are reached, the product is cooled quickly to stop fermentation. The whey is “immobilized” within the curd globules before it has a chance to get away. These globules of curd are not robust. Temperature changes weaken the bonds and allow trapped whey to escape curd’s milky grasp. Gravity, too, can overwhelm the curds’ ability to hang onto the whey. Such mechanical curdling is called syneresis.

Because most consumers don’t like the appearance of whey in their yogurt, producers add a variety of thickening agents — fruit pectin, various starches — to toughen up the curd. But now that I know whey is okay, I don’t think I mind.

*The tubs, after a turn through the dishwasher, make great paint or varnish pans. Or you can use them in the pantry to store granola.