Yosef Karo

“ But if a non-Jew takes a break, the Jew needs to be there, because it is like the case of the non-Jew's house. And even a Jewish child will suffice, because the non-Jew appears before him. In any case, if a Jew is not present until after he has finished milking, this milk is considered the milk of non-Jews that is forbidden, even thought no non-kosher animal exists in his herd. Milk of a non-Jew makes vessels non-kosher when they are cooked in them, just as any prohibited food, even though this is only an uncertainty whether he has mixed in something non-kosher. ”

“ Cheese made by non Jews was forbidden because that they are produced with the dried stomach of an animal that was not correctly slaughtered. And even when the cheese is produced using vegetarian rennet it is forbidden. ”