Whey refers to the watery portion of milk remaining after coagulation of the casein proteins (the process commonly known as “curdling”) occurs. The exact makeup of whey is dependent on the source of milk and the manufacturing process used. Whey commonly includes a rich blend of lactose (a carbohydrate sometimes referred to as “milk sugar”), most of the milk minerals, some of the milk fat, and most of the soluble, non-casein milk proteins known as whey proteins.
Whey is created during the cheesemaking process when fluid milk, which includes caseins and whey proteins, is turned into cheese with the addition of specific bacteria and enzymes. As these bacteria metabolize the lactose in the milk, lactic acid is produced.
This lactic acid reduces the pH level of the milk from around 6.7 to a level of approximately 5.3, which causes the casein proteins to coagulate. Due to their structure, whey proteins do not denature at pH 5.3, however they are trapped within the casein gel that forms. Cheese manufacturers cut this gel, releasing most of the whey and accompanying proteins from the casein curd. The whey is drained from the curd and used for processing into a variety of ingredients. Producing a pound of cheese results in about nine pounds of whey.
Whey is dried through a variety of processing techniques. The use of a dry product instead of a liquid whey simplifies use, handling, storage, and has a longer shelf life. Different processing procedures affect whey’s caking tendency, lactose crystallization rate which can affect crystal size and mass of crystals which affects whey quality, freewater content and other factors important to food technologists. Whey manufactured by different methods and suppliers may function differently in applications. It is important to find a whey ingredient that works best with your application.