Whey

The thin, yellowish-green liquid formed by coagulation of milk during cheesemaking, left behind when the solid curd is removed. Once discarded as a polluting waste, it is now a valuable raw material carrying lactose, minerals, and high-quality whey proteins. Modern dairies fractionate it by ultrafiltration, ion exchange, and evaporation into concentrates, isolates, and lactose, turning a disposal problem into sports nutrition, infant formula, bakery, and confectionery ingredients. Sweet whey from rennet cheeses and acid whey from fresh cheeses and Greek yoghurt differ in composition and handling, and the recent surge in Greek yoghurt production has made acid whey utilisation an industry-wide technical challenge. Its high biological oxygen demand still demands responsible effluent management.