Whey cheese is a dairy product made of whey, the by-product of cheesemaking. After the production of most cheeses, about 50% of milk solids remain in the whey, including most of the lactose and lactalbumin.[1] The production of whey cheese allows cheesemakers to use the remaining whey, instead of discarding it as a waste product.
There are two fundamentally different products made of whey and called whey cheese:[2]
Albumin cheese, made by coagulating the albumin in the whey with heat and possibly acid. Examples include ricotta and mizithra.[3] Lactose content is low.[4]
Norwegian brunosts ("brown cheese"), made by boiling down the whey to concentrate the sugar, and consisting primarily of caramelized milk sugar. Mysost is such an example. Since these are not primarily made of coagulated milk proteins, they are technically not cheese.[3][5] Lactose content is high.[4]
Two different kinds of whey cheeses are made, through different processes:
Coagulated (albumin) cheese
To produce coagulated whey cheese, heat and optionally acid is used to coagulate the whey. This type has a relatively low lactose content and a white-to-yellowish color.[4] It is possible to ripen albumin cheeses.[3] In addition to whey, the Codex Alimentarius[clarification needed] allows the use of milk, cream, and buttermilk, plus sodium chloride and starter culture. The whey can be pre-concentrated.[4]
Fresh albumin cheese is soft. It contains a lot of moisture and expires quickly. Ripened hard varieties have a much lower moisture content, making them preservable for much longer.[citation needed]
The production yield of coagulated whey cheese is generally lower than ordinary cheese, as whole milk contains only 1% whey protein.[citation needed] Yield is dependent on the composition of the whey, the addition of milk or cream, the production technology, and the composition (moisture content) of the final product. With efficient modern methods such as ultrafiltration, 10 to 20% of solids or more remain after the whey is mixed with cream and reduced.[7]
Concentrated cheese
To produce a brunost, the whey is simply concentrated by boiling down and then molded. Cheeses produced using this method possess a relatively high lactose content. Typically, they have a yellowish-to-brown color and possess a sweet, cooked, or caramelized flavor.[3][5] Pre-concentrated whey may be used. Additional allowed ingredients under the Codex Alimentarius are cream, milk, and other raw materials obtained from milk, plus sugar.[4]
Lactose content
Because almost all varieties generally contain significant amounts of whey, they are unsuitable for consumption by people who are lactose intolerant. Brocciu is lower in lactose.[8]