When cheese is made, a chemical is used to coagulate the proteins in skim milk to form curds. The liquid that is leftover is called whey and contains lactose and whey protein. In modern dairies, the proteins in skim milk are concentrated before they are sent to cheese or yogurt makers. This is done mechanically with filtration. The liquid that's removed is known as milk permeate since it permeates through a membrane along with much of the lactose. Milk permeate is less acidic than whey and contaiins no cheesemaking by-products. We found alcohol made from milk permeate to be of much higher quality.