Acid Whey

Acid Whey: Nutritional Reference

Acid whey is the liquid byproduct produced when milk or cream is coagulated by acid — either added directly (lemon juice, vinegar, acid) or produced biologically through lactic acid fermentation — and then drained from the resulting curds. It is generated in the production of fresh acid-set cheeses such as cottage cheese, ricotta (partially), cream cheese, quark, and acid-set fresh cheeses, as well as in the production of strained yogurts such as Greek yogurt. Acid whey is characterised by a lower pH (more acidic) than sweet whey (which comes from rennet-coagulated cheeses), and contains more lactic acid and a higher proportion of the milk's calcium (which dissolves in acid conditions and passes into the whey rather than remaining in the curd). The dramatic growth of the Greek yogurt market in the United States since the late 2000s has created a significant acid whey disposal challenge for the industry — producing a kilogram of Greek yogurt generates approximately three kilograms of acid whey, and the volume of production has outpaced the industry's capacity to use or process it. Acid whey cannot easily be spray-dried into powder like sweet whey due to its high lactic acid content, making it more challenging to valorise commercially.

Nutritional Composition of Acid Whey

Acid whey provides 24 kcal and 0.76 g of protein per 100 ml, with just 0.09 g of fat — a very low-nutrient liquid. It contains lactose as its primary energy source, alongside lactic acid, dissolved calcium (at higher levels than sweet whey), phosphorus, potassium, and small amounts of water-soluble vitamins. The protein content is low as most protein remains in the curd — what remains is primarily denatured protein fragments and peptides.

Uses of Acid Whey

In home cheesemaking and yogurt making, the whey drained from straining projects should be used rather than wasted. Add to bread dough in place of water for a subtle tangy flavour and tender crumb. Use to cook grains — porridge, rice, and barley cooked in whey gain flavour and extra minerals. Add to smoothies for a low-calorie liquid base. Use to water acid-loving plants in the garden. Historically, whey was consumed directly as a drink in many European cultures — "taking the whey cure" was a fashionable health practice in the eighteenth century at spas including Bath. The lactic acid and mineral content gave it a reputation as a digestive tonic.