QUESTION: I bought two packages of cheese, which I thought were kosher. Subsequently I discovered that only one was kosher, and the other was not. I took some slices of cheese from one of the containers and used it to make a cheese sauce. I do not remember which package I took the cheese from. Can I eat the sauce? Or must I throw out the sauce and kasher the pot?
ANSWER: One would assume that it would be permissible to use the sauce, since gevinas Akum (non-kosher cheese) is Rabbinically prohibited and the principle of “safek d’rabbanan l’kula” (we are lenient regarding doubts that involve a rabbinic prohibition) should apply. Therefore, the halacha should be that since the status of the cheese sauce is unknown, it should be permitted to be eaten.
However, the Shach (Klalei Sfek Sfeika) writes that gevinas Akum is an exception to the rule of safek d’rabbanan l’kula for the following reason. Before the decree of gevinas akum was instituted, non-Jewish cheese was permissible because it was not certain that the coagulant was rennet, and even if it was, rennet is used in only very small quantities which are botel on a Biblical level. When the Rabbis decreed that gevinas akum was prohibited, they treated the cheese as if it were certain that rennet was used above the bitul threshold. Once the Rabbinic prohibition was enacted, we can no longer view the cheese as a safek d’rabanan.
The cheese sauce should be discarded, and the pot must be kashered.