orange precursors the carotenes, which are
found in green feed and give milk and undyed
butter whatever color they have. Breeds differ
in the amount of carotene they convert into
vitamin A; Guernsey and Jersey cows convert
little and give especially golden milk, while at
the other extreme sheep, goats, and water
buffalo process nearly all of their carotene, so
their milk and butter are nutritious but white.
Riboflavin, which has a greenish color, can
sometimes be seen in skim milk or in the
watery translucent whey that drains from the
curdled proteins of yogurt.
Milk Sugar: Lactose
The only carbohydrate found in any quantity
in milk is also peculiar to milk (and a handful
of plants), and so was named lactose, or “milk
sugar.” (Lac- is a prefix based on the Greek
word for “milk”; we’ll encounter it again in
the names of milk proteins, acids, and