הלכה על עבודה זרה 2:5

The Rambam (Hilchot Ma’achalot Asurot 3:12-13) notes that there should be more reason to allow cheese produced by a non-Jew than milk produced by a non-Jew, because milk from a non-kosher animal cannot be made into cheese. Nevertheless, Chazal prohibited consuming cheese produced by a non-Jew. Although the Mishnah (Avodah Zarah 2:5; see Avodah Zarah 35a) indicates that Chazal at first concealed the reason for this prohibition, the Gemara (Avodah Zarah 35a-b), searching for the correct explanation, cites a plethora of reasons. It suggests that the non-Jews curdled the milk with the stomach lining from niveilot (animals that were not properly slaughtered); that the non-Jews did not take adequate care to cover the milk that would be used to make cheese, leading Chazal to worry that snakes would release their venom into the uncovered liquids;¹This explanation assumes that the decree on cheese is basically an extension of the decree against mayim megulim (water that was left uncovered), which Chazal also forbade out of concern for snake venom. that the non-Jews smoothed over the cheese with pig fat; that there might be leftover drops of milk in the cheese that did not curdle, and these drops might have been from a non-kosher animal; and that the non-Jews made the cheese using non-kosher vinegar.

There are two unresolved debates concerning the production of kosher cheese. The Rama (Y.D. 115:2) rules (and notes that this is the common custom) that it is sufficient for a Jew to monitor the cheese-making process to render the cheese kosher. According to the Rama, the prohibition of gevinat akum parallels the prohibition of chalav akum, for which supervision likewise suffices to permit the product. The Aruch Hashulchan (Y.D. 115:19) cites the Rambam in his commentary to the Mishnah (Avodah Zarah 2:5 s.v. Amar Lo), who writes explicitly in accordance with the view of the Rama. The Shach (Y.D. 115:20), on the other hand, requires either Jewish ownership of the cheese or active participation of a Jew in the cheese-making. According to the Shach, then, the rules of gevinat akum parallel those of pat akum (bread baked by a non-Jew) in that Jewish participation is required to render the product permissible.

The Shach offers a textual proof to his ruling from the language of the Mishnayot that present the prohibitions of chalav akum and gevinat akum. The Mishnah (Avodah Zarah 2:6) that presents the former prohibition states explicitly that the milk is prohibited only if a Jew does not watch the milking, whereas the Mishnah (Avodah Zarah 2:5) that presents the prohibition of gevinat akum states simply that the cheese is prohibited, making no distinction as to whether a Jew must watch the cheese-making process or not. The Shach, accordingly, concludes that Jewish ownership or active participation is indeed required to permit us to eat the cheese.⁶See, however, the comments of Rav Yonatan Eybeshitz (Mateh Yonatan Y.D. 115:2), who seeks to refute this proof.