Continuing our cheesy alphabet, today's object is a liquid obtained in the manufacture of butter. In composition it is close to skimmed milk, but in contrast it is rich in phosphopeptides. In powdered form, it is mostly used in cattle feed or reconstituted milk. It is also an emulsifier (on account of its phospholipids). When concentrated through ultra filtration, it is also used as an ingredient in low-fat butters.
It can also be used in producing re-baked cheese, like other products derived from serum. It was the basic ingredient of gaperon, which comes from the Auvergne (though not any more). Farmers used to use it as animal feed (pigs). It can change in form from region to region.
In Germany, buttermilk is used as a milky drink, as the butter starter culture gives it a special taste, a little sour but appreciated by consumers.