Whey is the leftover liquid from making cheese. Cheeses made with rennet such as Gouda, cheddar, mozzarella and Swiss produce what is called sweet whey, while cheeses set with acid, such as chevre, cottage cheese and cream cheese, produce acidic whey. While whey was originally considered a waste byproduct of cheese production, there are some food uses for it.
Adding Nutrition to Other Foods
Each cup of either sweet or acid whey provides about 2 grams of protein, as well as significant amounts of calcium, potassium, phosphorus and riboflavin. You can use whey instead of milk, water or lemon juice to raise the health benefits of savory dishes or smoothies.
Soaking foods containing phytates, such as whole grains and beans, in whey can help make them easier to digest and make it easier to absorb the nutrients they contain. You can also use whey combined with salt to ferment foods, such as sauerkraut.
Making Whey Cheese
You can use the whey from cheeses made with rennet to make other types of cheeses, including ricotta, mizithra, mysost and gjetost cheeses.
Of you can reuse the whey in future batches of cheese to improve its texture and nutrient profile. This has to be carefully done, however, to avoid it becoming contaminated and ruining future batches of cheese.
Making Sweet Treats
You can use sweet whey to make desserts as well. First, the whey needs to be concentrated with added sugar to make sweetened condensed whey, and this can be turned into candies like taffy, caramels and fudge. In Latin America, they also use whey combined with sugar to make a syrup called dulce de leche, which can be further concentrated to form a solid candy. (ref 4 p5)
Besides adding whey to smoothies, you can use it to make fruit-flavored beverages by adding fruit purees and citric acid or to make low alcohol beer, wine and champagne.
Whey also can be included in animal feed, used to produce biogas and as a fungicide or insecticide.