Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain.
The fatty acids of butterfat are typically composed as follows (by mass fraction):
As shown above, the composition of fats in milk is usually discussed in terms of the fatty acids. Fatty acids do not occur as such in milk (and rarely in any food). Instead, they are incorporated into compounds called triglycerides.
U.S. standards
In the U.S., there are federal standards for butterfat content of dairy products. Many other countries also have standards for minimum fat levels in dairy products. Commercial products generally contain the minimum legal amount of fat with any excess being removed to make cream, a valuable commodity.
MilksSkim milk contains less than 0.5% fat, typically 0.1%Lowfat milk contains between 0.5–2% fat; 1% and 2% varieties are widely marketedWhole milk contains at least 3.25% fatCheesesDry curd and nonfat cottage cheese contain less than 0.5% fatLowfat cottage cheese contains 0.5–2% fatCottage cheese contains at least 4% fatSwiss cheese contains at least 43% fat relative to the total solidsCheddar cheese contains at least 50% fat relative to the total solidsFrozen dessertssherbet contains 1–2% fatLowfat ice cream, also called ice milk, contains no more than 2.6% fatIce cream contains at least 10% fatFrozen custard, like ice cream, contains at least 10% fat, but it also must contain at least 1.4% egg yolk solidsCreamsHalf and half contains 10.5–18% fatLight cream and sour cream contain 18–30% fatLight whipping cream (often called simply "whipping cream") contains 30–36% fatHeavy cream contains a minimum of 36% fatManufacturer's cream (not federally regulated) contains 40% fatButter (including whipped butter) contains at least 80% fat
