Notes
Dairy milk is composed of 87 percent water, 3.2 percent
protein, 3.9 percent fat, 4.8 percent carbohydrate,
and roughly 1 percent minerals and vitamins. The fat
in milk is a mixture of lipids. Triglycerides are the
main type of lipid. Lipids have a lower density than
water, so when raw milk sits for several hours, the
cream (butter) will rise to the top.
The density of cream is the basis for butter making.
The cream is churned to separate the butter
(solids) from the buttermilk (liquid). Butter contains
at least 80 percent milk fat by weight. The butter can
be salted and poured into molds for further processing.
Butter remains solid when refrigerated but
softens to a spreadable consistency at room temperature
and melts to a thin liquid consistency at 32 to 35
˚C (90 to 95 ˚F). Butter is generally pale yellow but can
vary from deep yellow to nearly white. The yellow
color is the result of the b-carotene in the grass that
dairy cows eat.
Homogenizing milk prevents the cream (butterfat)
layer from separating from the milk. Homogenizing
breaks down the fat globules into smaller globules and
disperses them evenly in the milk. The smaller globules
will not rise to form cream during normal storage
conditions.