The Shulchan Aruch writes in YD 115:2: "Chazal forbade gevinas akum (cheese made by a non-Jew), because they coagulate it with ohr keivas neveilah (the stomach lining of their slaughtered animals). And even if they coagulated it with a plant agent, it is still forbidden." The Rema agrees that this is the established custom in virtually all Ashkenazi communities as well.
is an example of a gezeirah (decree) that is called a "davar she'b'minyan." It means that even though Chazal had a particular reason in mind when making the original gezeirah on cheese, once they decreed it, it applied as a blanket gezeirah on all types of non-Jewish-made cheese, regardless of how it was made. Nowadays in the US, instead of using the stomach lining (called "rennet"), they use an artificial agent. Nonetheless, it is still forbidden because, as we mentioned, gevinas akum is a "davar she'b'minyan."
What is the background of this gezeirah? The Gemara in Avodah Zora (35a) says that Chazal forbade gevinas akum and then lists six opinions as to why. The six opinions are:
- Perhaps a venomous snake drank from the milk that was used to make the cheese
- Perhaps it contains some drops of milk from a non-kosher animal
- Perhaps they coagulated the cheese with the stomach lining of a neveilah
- Perhaps they smoothed the cheese with pig fat
- Perhaps they coagulated the cheese with vinegar made from yayin nesech
- Perhaps they coagulated the cheese using liquid that came from fruit that was orlah
Shmuel is the one who holds that the reason was because perhaps they coagulated the cheese with the stomach lining of a neveilah. The Rif and the Rambam both rule that the halacha is like Shmuel and this is why the Shulchan Aruch mentions only this reason out of the six.
Even if there was non-kosher rennet mixed in to coagulate the cheese, why should the cheese be forbidden? Surely only a tiny amount was used and therefore the rennet should be nullified because it is less than one in sixty? The answer is that since the rennet causes the cheese to become hard, its effect is recognizable and thus it cannot be nullified, irrespective of the small proportion it makes up.
Why does the Gemara only mention ohr keivas beheimah "neveilah?" A neveilah is an animal that wasn't slaughtered according to halacha. A neveilah's meat is forbidden from the Torah. The Gemara implies that the stomach lining of an animal that was slaughtered in accordance with halacha is ok to use in making cheese?! But surely there must be some issue of basar b'chalav with this?
Tosfos ask this kasha (difficulty). They answer that Shmuel specifically mentioned "neveilah" because it is a Torah prohibition. But there is no Torah prohibition of basar b'chalav in the making of cheese because no heat is involved. Meat and milk mixed together when cold is only forbidden m'derabbanan.
The Tzvi L'Tzaddik asks a kasha on Tosfos. Even if the cold mixture of meat and milk is not forbidden on a Torah level, it is still assur me'derabbanan and should forbid the cheese. He answers that it must be that Tosfos hold that since there is a combination of two derabbanan prohibitions ((1) cold meat and milk & (2) coagulation), Chazal did not forbid this. Therefore if kosher rennet had been used to make the cheese, the cheese would've been kosher.
So, in summary, the only concern that Chazal had with non-Jewish cheese was that it might have been made with rennet from a neveilah. Because of this concern they forbade all forms of cheese made by a non-Jew.
Next week we will look at how the gezeirah applies to "hard" and "soft" cheeses.