Buttermilk and butter serum are both by-products of the milk fat
industry. Buttermilk is the liquid phase released during cream churning
in the process of butter manufacture. Butter serum is the aqueous phase
obtained after melting and centrifugation of butter in the production
process of anhydrous milk fat (AMF). AMF consists of a 99.9% pure
milk fat product with specific techno-functional properties like high
resistance to heat and mechanical treatments (Boutonnier, 2008;
Vanderghem et al., 2010). The large production of butter and AMF
worldwide (10 Mt of butter and AMF in 2013, Cniel, 2015) results in a
large production of buttermilks and butter serums which are mainly
mixed together (with a higher proportion of buttermilk due to a higher
production of butter) and spray-dried into powder for animal feed.
In terms of composition, buttermilk and butter serum are very close
to skimmed milk when focusing on proteins, ashes and lactose content