Dairy milk is composed of 87 percent water, 3.2 per cent 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.