Why does raw milk separate into skim milk and cream rather than skim milk and butter? Why is a second step necessary to churn out butter? And what difference if any is there between skim milk and the buttermilk* left over from butter churning?
*The original definition of “traditional” buttermilk, the liquid leftover from making butter. Modern “cultured” buttermilk is basically fermented milk.
Thanks markn+. Does that make the liquid portion of cream just what amount of skim milk the globules “drag” with them when cream separates?
Think of it more as whatever fills the spaces around the cream globules - like if you had a pile of marbles, all the air spaces would be that liquid.
And the buttermilk left over from butter churning is essentially fermented skim milk.
Apparently, during the time when cream separates from the rest of the milk, it begins to ferment, and traditional butter making allows that to continue in the collected cream because it makes butter easier to churn.
Yes and no. Before refrigeration and mechanical separation, by the time cream rose it had already started to ferment, or “culture”. On the other hand if you start with modern fresh cream it won’t have fermented yet. Modern cultured buttermilk is an imitation of traditional buttermilk by fermenting skim milk.