Notes on cultured butter & buttermilk
Butterfat content of milk has been rising over the years due to genetic improvements in dairy herds. The average butterfat yield has risen from about 3.5% to almost 5%.

Pasteurized whole milk begins its modern process to butter by being forced through continuous separators (centrifuge) @ 30,000 RPM. The separator yields 40% butterfat cream (aka: heavy or whipping cream). Yields above this cannot be obtained because of the mechanical limitations of the separator. The 40% cream goes directly into continuous or ribbon churns. They operate much like modern continuous ice cream freezers. The cream is pumped into one end and "sweet cream" butter and high fat buttermilk come out of the other in a continuous operation. The buttermilk is high fat because ribbon churns are not very efficient at churning all of the butterfat into butter. This buttermilk is then re-separated to remove the excess butterfat, and is dried (uncultured) for industrial applications such as commercial ice cream and baking mixes, as well as consumer package goods such as buttermilk pancake and baking products. The butter made by this process is called "sweet cream" because it was not made from cultured or acidified cream.

The traditional method of making butter differs both in method and the product produced. Once the milk has been separated, the 40% cream is put into holding tanks for a day before it is churned to butter. This allows the cream to settle from the agitation of the separation process, and gives the butter maker time to "culture" his cream. The culturing of the cream before churning has two practical benefits. First, the acidification of the cream with the addition of a lactic acid producing culture aids in the separation of the butterfat in the churning process (remember, the cream is 40% butterfat and 60% skim milk). Secondly, the added live cultures consume milk proteins to produce this lactic acid, and thus yields a more "pure" butter that has a longer storage life. It is the milk proteins that "spoil" or ferment, rancidifying the butter. Other than these practical benefits, culturing the cream before churning gives the butter a very unique flavor; different from that which is in the grocer's dairy cases today.

This "cultured" cream is then batch churned for about 30 minutes. It is only in the last two minutes of the churning process that the butter starts to form in the churn. The agitation of the churning process breaks down an emulsifying membrane around the droplets of butterfat, allowing the butterfat to solidify as butter. These now "free" emulsifiers are then skimmed off with the lowfat buttermilk. After the buttermilk is removed from the churn, the butter is then washed with water to remove any residual milk solids to eliminate the proteins that might accelerate the spoilage of the butter.

This is the way that butter used to be made in the USA, and is how it is still produced in much of Europe. Before the advent of the large commercial dairies, Minnesota and Wisconsin used to be dotted with small creameries; each with its own particular "flavor" of butter made from closely guarded family cultures. These cultures were carried into the churned buttermilk during the butter-making process as well. Although buttermilk is a very thin liquid (resembling skim milk) as it is removed from the butter churn, it is the continuing action of the live cultures that create the tart, thick beverage that we know as buttermilk. However, with the demise of "cultured" butter with the modernization of Americas dairy industry in the 40's and 50's, and the fact that it takes a lot of milk to make a small amount of real buttermilk, modern buttermilk (cultured skim milk) was created by artificially adding lactic acid producing cultures to skim milk. The resulting beverage had similar taste and textural characteristics to the real buttermilk, but lacked the emulsifying properties that made the old fashioned buttermilk such a prized ingredient for cooking and baking.

One gallon of milk yields about 3/4 pint of 40% cream (heavy cream), which can be churned into 1/3 lb. of butter (1 1/2 sticks) and about 1/2 pint (1 glass) of buttermilk. So 1 gallon of milk can yield only about 1/2 pint of real buttermilk, but 7 1/4 pints of skim milk that can be artificially cultured into today's buttermilk. It is only that, decades ago, the term 'buttermilk' became the generic term for cultured skim milk that the name was "grandfathered" into today's dairy laws. It could not have passed our current labeling requirements.