The array of opinions as to the kashrut of cheese has led to many different standards. There are those who consider any cheese made by a non Jew to be forbidden, regardless of the ingredients. This view is the one accepted by most Hareidi (Ultra Orthodox) communities. There are those that require that there be no non kosher ingredients (rennet from a non kosher animal), but acceptable even if made by non Jews. This is the standard in many European Jewish communities, as well as the standard of some of the secondary kashrut agencies in the U.S. There are those who regard any and all cheese, no matter who made them, or with what rennet. Rabbenu Tam, who not only permitted these cheeses but actually consumed them, came to the conclusion that this enactment wasn't based on any halachic considerations, but rather on the obscure prohibition of "Gilui"; any beverage that was left uncovered and unguarded, for fear that a snake or scorpion may have put its venom into the milk. As this would be exceedingly rare in modern conditions (ancient windows had no glass; they were just openings), most poskim say that it can be ignored today. That was Rabbenu Tam's reasoning for permitting all cheese. A few years ago, I asked a rabbi who had "supervision" on a non Jewish cheese factory about his standards. He told me that there is no actual supervision. he just is certifying that only kosher enzymes are used. I asked him what about the fact that it is made by non Jews? He replied "it's not made by non Jews. It's made by a computer!" Many, but not all, cheese makers in the U.S. use "microbial enzymes". That actually means enzymes from bacteria that have been genetically engineered to produce secretions similar to rennet. This eliminates the problem of the permissibility of animal rennet. The major kosher cheese brands in the U.S. now use this kind of enzyme. However, it is illegal in Europe. The late Rabbi Shlomo Goren, a cChief Rabbi of Israel from the early '70s to the early '80s, permitted non Jewish cheese if the manufacturing company had a single Jewish stockholder, as that is no longer "non Jewish"cheese. Rabbi J.B. Soloveichik had a different approach. He believed, and taught his students, that since cheese is made in a vastly different way from how it was in Talmudic times, that it is not halachically considered cheese at all, and the enactments for cheese simply do not apply. Only gourmet cheeses, actually made in the stomach of a calf, would be a problem. A story, denied today, but which I heard from eye witnesses, is that when anyone came to his home to discuss something, he would put in front of the guest a cheese sandwich, and made obvious that the cheese was from Kraft (a major non Jewish cheese producer). If he saw that the guest was hesitating, he would say "If you don't eat it because you don't like it, it is b'seder (alright). But if you like it but don't eat it, then EAT IT!!!" However, when someone who was not his student would ask, he always said:"Ask the OU". The OU, largely made up of students of his, took the stance that the cheese must use either rennet produced from a properly slaughtered kosher animal (or non animal "rennet"), and have a Jew somehow involved in the cheese making,even if only present in the building. Many, outside Modern Orthodox circles, question the validity of that approach.A few poskim, relying on the fact that many authorities permitted soft cheese made by a non Jew, expanded the concept of "soft cheese" to include all non aged cheese. One prominent rabbi even permits buying cheese pizza in a non kosher store. (I will deal with the issue of utensils in another two posts). All that I have written is assuming that we are not dealing with a cheese with actual non kosher ingredients, such as wine or meat (present in some gourmet cheeses). My hope is that everyone can see that none of these standards is "off the wall", and result from different halachic approaches.Nevertheless, in the U.S., where the OU standards are assumed to be the only valid one's, your neighbors may look askance at any other cheeses. An exception is Boston, where Rav Soloveichik served for many years as rabbi. Large portions of the local Orthodox community still follow his lenient ruling.