Gevinat Akum
It is forbidden to eat cheese that was produced by non-Jews, a rabbinical enactment known as "gevinat akum" ("cheese produced by non Jews"). This is true even if one is certain that all of the ingredients used in the making of the cheese were completely kosher. There are a number of reasons why the rabbis instituted a ban on gevinat akum, as we will see.
The main reason was the concern that the milk used to make the cheese may have been curdled with the stomach linings ("rennet") of non-kosher animals, a cheese-making method which was quite common in ancient times.[1] There was also the obvious concern that the milk used to produce the cheese may have been from non-kosher sources or that non-kosher ingredients or curdling agents might have been added to the cheese.[2] Finally, cheeses were very often coated, sealed, or preserved with forbidden fats. There are also those who say that the true reason for the institution of gevinat akum was never intended to be known and remains a mystery.[3]
It is actually quite surprising that the rabbis were so strict with a natural product such as cheese. This is because it is simply not possible for cheese to be made from anything other than kosher milk, as milk obtained from non-kosher animals does not properly solidify into cheese.[4] Although there have been authorities who advocated permitting gevinat akum if it could be determined that none of the concerns mentioned above applied,[5] the halacha is not in accordance with this view. As such, all cheese produced by non-Jews remains forbidden regardless of all other considerations.[6]
It is not necessary for a Jew to actively participate in the entire cheese-making process in order to render the cheese kosher. According to many authorities, it suffices if a Jew merely supervises the cheese making.[7] Other authorities are more strict and rule that a Jew must actually participate in the cheese making process by adding the enzyme that forms the cheese.[8] Cheeses that are produced in Jewish-owned factories are kosher even if the cheese is made by non-Jewish workers. It goes without saying, however, that one must be sure that all the ingredients are kosher.[9]
A number of authorities are of the opinion that the restrictions of gevinat akum only apply to hard cheeses. This is because stomach linings were only used in the production of hard cheese. Soft cheeses, however, are made by simply allowing the milk to ferment and curdle on its own.[10] Nevertheless, common custom is not like this view and most kosher certifying agencies ensure that the restrictions of gevinat akum are applied in the production of soft cheeses, as well.[11] In an emergency one can allow children to eat gevinat akum as long as all the other ingredients in the cheese are kosher.[12]
Somewhat related to the issue of gevinat akum is that of butter. Although it is certainly preferable for butter to be produced by Jews and to be kosher certified, it is technically permitted to consume butter produced by non-Jews. This is because the sages did not extend the restrictions of gevinat akum to include other dairy products, such as butter. Furthermore, it is simply not possible for butter to be produced from the milk of non-kosher animals and therefore there is no concern that non-kosher milk might have been used. It goes without saying, of course, that all of the other ingredients used in the butter must be kosher.[13]
[1] Avoda Zara 35a.
[2] Avoda Zara 35a.
[3] Avoda Zara 29b,35a.
[4] Rambam, Hilchot Ma'achalot Assurot 3:12, 13.
[5] Tosfot, Avoda Zara 35a.
[6] YD 115:2.
[7] Rema, YD 115:20.
[8] Shach, YD 115:20.
[9] Shach, YD 115:20; Chochmat Adam 87:7.
[10] Igrot Moshe, YD 2:48.
[11] Aruch Hashulchan, YD 115:16; Chochmat Adam 53:38.
[12] Yabia Omer, YD 5:11.
[13] YD 115:3. See also Yabia Omer, YD 7:5.