The three main types are uncultured, cultured, and European-style.
Uncultured or sweet cream butter, churned from pasteurized cream
is the supermarket standard.
Cultured butter is made from cream that has been fermented with
'good bacteria', and it is churned longer and slower, according to
the American Butter Institute.
European-style butter is made similarly, but not all
European-style butters are cultured.
Both cultured and European-style butter have less water, more
butterfat (from 82 to 87 percent) and a tangier, deeper flavor
than mellow, sweet cream butter. There are salted and unsalted
versions of each.
There are other variations of butter, such as 'light' butter,
which has more water and about half the fat and calories than
regular butter, but because it is made to be spreadable, it also
contains preservatives and emulsifiers. Whipped butter gets its
light, spreadable texture from nitrogen whipped into it after
churning. USDA-certified organic butter comes from cows raised on
organic, pesticide-free feed, without antibiotics or growth
Salt adds flavor and extends
the shelf life of butter. According to the US Butter
Institute, unsalted butter has a two-week refrigerator shelf life
and salted butter two months. The USDA is a bit more generous,
giving a range of one to three months. What you buy from the store
has probably been in cold storage for longer than that. If you are
not using your butter quickly, it will stay fresher if you store
it in the freezer, where it will keep for up to nine months.