product made in a process called butter  churning, which is a stirring process  

that separates the solid butter from the  liquid buttermilk. According to US law,  

butter must contain at least 80% fat. The color  of the butter can range from white to dark yellow,  

depending on what the cows eat. Store-bought  butter is often pasteurized, a process in  

which cream is heat-treated to destroy harmful  microorganisms. Bacteria can be introduced into  

butter when food handlers at home or restaurants  handle butter. Harmful bacteria commonly found in  

butter include Staphylococcus aureus, Listeria  monocytogenes, and Yersinia enterocolitica.