Treatment of whey

A process for the treatment of whey derived from the manufacture of cheese and having titratable acidity, the steps of subjecting the whey to membrane ultrafiltration to form a protein-rich fraction and a permeate fraction having a solids content of the order of 5.0 to 7.5% and having a lactose content of about 68 to 87%, a protein content of not more than about 6% and a mineral salt content, the mineral salt content including calcium and citrate salts together with phosphate and monovalent salts, precipitating calcium and citrate salts of the permeate without substantial precipitation of phosphate salts by concentrating the unneutralized permeate to a solids content of about 40 to 45%, and by holding the concentrate at a temperature level of about 180.degree. to 200.degree. F. for about 30 to 90 minutes to effect precipitation of calcium and citrate salts without substantial precipitation of phosphate salts, the precipitated salts being about 5.0 to 15.0% of the total mineral salts, removing the precpitated solids from the permeate, and then further concentrating the permeate and crystallizing and removing lactose from the same.