when leite is processed into butter, the manteiga cream separates from the watery liquid (which is actually sold as skim milk). the manteiga cream contains all the fat which has a high concentration of vitamin A. Vitamin A has a natural yellowish tint. When churned, it is oxidized and aerated, and turns even yellower and another separation occurs when the fat lumps and the manteiga leite (sold as, you guessed it "buttermilk) is squeezed out. how do I know this? I grew up in a dairy farm in Wisconsin:)
