src: Whey is produced by putting a coagulant in milk; the part that coagulates is cheese, and the one that doesn’t is the whey or more precisely the fractions of whey.
tgt: On obtient le whey quand on met un agent coagulant dans le lait; la partie qui coagule est le fromage, et celle qui ne coagule pas est le whey ou plus précisément les fractions de whey.