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Butter is a dairy product made by churning fresh cream. It consists primarily of butter fat (>80%) in emulsion with water and milk proteins. It is used as a condiment and for cooking in much the same ways as vegetable oils or lard.
Butter is made by agitating cream, which forces the fat droplets to merge together and separate from the liquid portion. This can be done in many different ways and with a variety of tools.
To make homemade butter, fill a jar ⅓ full with heavy cream. Shake the jar until a solid mass forms. If the cream becomes too thick to shake easily, add a bit of water. Pour off the liquid and use a spatula or spoon to collect the butter. This soft butter can be served on its own, or mixed with herbs or spices. You can also add flavor by pouring a small measure of flavored liquor in with the cream.
Butter is is solid but soft at room temperature, and it melts easily. It is generally pale yellow, but it can vary from deep yellow to nearly white depending largely on what type of food the animals were eating. For example, butter is typically paler in the winter, when dairy cattle feed on stored hay rather than fresh grass.
In Australia both salted and unsalted butter are readily available, and no preservatives, additives or colorings are allowed in standard butter unless they are labeled as a 'spread'.
European butter typically contains 82% to 84% butterfat and comes in salted and unsalted varieties. The greater portion of butterfat makes European butter taste richer than American butter.
Butter sold in United States markets is typically 80% to 82% butterfat and salted, unless marked otherwise. Flavorings, colorings, and preservatives may also be added. Butter with a fat content above 82% is referred to as 'dry butter' or 'European-style', and it is available in specialty shops. Butter in the United States is generally sold in 4-ounce sticks wrapped in wax paper, although it is sometimes sold in larger blocks.
In South Asia, butter is often melted and processed to remove the milk solids and remaining water. This is often known as ghee or clarified butter.
Butter is very stable and has a long shelf-life. Because the fat can eventually oxidize and turn rancid in contact with air, butter should be kept wrapped or covered. It will keep well for months when wrapped and stored in the fridge or freezer.
Butter is widely used in cooking and baking for its flavor and texture. It can be used to fry foods, although un-clarified butter burns easily and is more suitable for lower-heat cooking. It can also be used to thicken sauces and custards, and it adds tenderness and moisture to baked goods. In baking, the temperature and texture of the butter is often carefully controlled to affect the final texture of the baked product. Butter is also often used as a simple condiment, and it may be spread on bread products or stirred into dishes like pasta before eating.