QUESTION: Is butter considered a type of cheese? Must it be gevinas Yisroel?
ANSWER: Butter is not subject to the rule of Gevinas Akum. The manufacture of cheese involves the coagulation of milk protein, called casein. Casein can be coagulated by using non-kosher enzymes derived from the stomach flesh of neveilah animals (animals which did not undergo kosher slaughter), which would render the finished product non-kosher. Therefore, Chazal decreed that special onsite supervision is necessary, to ensure that kosher enzymes are used (Avodah Zarah 35b, Shulchan Aruch – Yoreh Deah 115:2).
Butter, however, is made by separating cream (fat) from milk and concentrating it into a solid through the churning process – not through coagulation. Since butter production never involves coagulation, Chazal did not subject butter to the rules of Gevinas Akum.
Nevertheless, butter requires reliable kosher supervision due to issues of cream sourcing, shared equipment, and the frequent presence of starter distillate – a kosher-sensitive flavor commonly added to butter.