Ask the Rabbi: Kosher conundrums

Why do many food labels on dairy products state that it is kosher for some but not others?

In principle, once a product is kosher, it should be permissible for all consumers.
However, as with other areas of Jewish law, disputes remain regarding the status of different ingredients and industrial processes. Occasionally, this stems from differences in historical customs between Ashkenazim and Sephardim, such as with kitniyot (legumes) on Pessah or the necessity of glatt meat. More complex disputes, however, relate to the status of gelatin and milk.
Gelatin is a protein substance derived from collagen, the tissue that connects bones, tendons and skin in animals. It is a valuable industrial ingredient because it forms a positive binding action while remaining transparent, flexible, and digestible. Gelatin is used in medicines (“gelcaps”), drinks, yogurts and other products, but is most famous as contributing the silkiness to desserts, such as marshmallows, chocolates and Jello.
Classically, gelatin was derived from the skin and bones of by-products of non-kosher animals: pigs, non-kosher species or animals slaughtered inappropriately (neveila). While Rabbi Haim Ozer Grodzinski discussed whether hard, dry bones from non-kosher animals are permissible (Ahiezer 3:33:5), this remains practically irrelevant in our case, since most gelatin derives from skin or soft bones with meat and marrow.
Nonetheless, a number of decisors declared gelatin as a permissible ingredient because of its complex production process that includes boiling water, acids and heat. Rabbi Tzvi Pesach Frank contended that since the substance becomes inedible (“like dry wood”) during this process, it loses its status as a nonkosher product (Har Tzvi YD 83). Alternatively, rabbis Ovadia Yosef (Yabia Omer YD 8:11) and Eliezer Waldenburg (Tzitz Eliezer Vol. 4 Introduction) contended that the product gets radically altered, thereby giving it a new identity (panim hadashot).
These claims were strongly challenged by Rabbi Aharon Kotler, who believed that gelatin was absolutely forbidden since its use as a central ingredient revitalized its original identity as a prohibited food (Mishnat Rabbi Aharon 1:16). Fellow American decisors rabbis Moshe Feinstein (Igrot Moshe YD 1:37, 2:27) and Yosef Henkin, while more moderate in their counterarguments, ultimately held the production process was insufficient to change its identity from its non-kosher origins.
The Israeli Chief Rabbinate relies on the lenient opinion for its standard (but not mehadrin) certification, yet insists on marking the label as permissible only for those who consume gelatin. Most American kashrut organizations do not certify standard gelatin products, but do allow a recent version of gelatin specially made from kosher animals. Its use, however, remains somewhat limited because of the additional costs of producing this material. When necessary, many decisors believe that gelcap tablets are permissible for medicinal purposes (Edut Leyisrael p. 177).
In theory, all milk that is extracted from kosher animals should be permissible, no matter who performs the milking. The sages, however, were fearful that non-kosher milk (from camels or horses, for example) might get mixed into kosher milk, and therefore ordained that milking must be performed or supervised by a Jew (Avoda Zara 35b). As such, unsupervised milk (halav akum) is entirely non-kosher (YD 115:1).
In the 17th century, Rabbi Hezkia de Silvia contended that such supervision was not necessary in areas in which non-kosher milk was not produced. While this leniency received much support (Shu’t Radbaz 4:74), it was challenged by many other scholars, including Rabbi Moshe Sofer, who contended that the sages allowed for no exceptions to their decree, which itself was made to prevent a remote possibility (Hatam Sofer YD 107). Historically, various communities adopted different stances on this question (Darchei Teshuva 115:6).
As milk production became more industrialized and mass produced in the 20th century, Rabbi Feinstein issued a landmark responsum which contended that governmental regulation and inspection (including severe penalties) provided sufficient supervision, even though inspectors only entered the process at the stage of production dairies, and not at the actual farms (Igrot Moshe YD 1:47- 49). While endorsed by Rabbi Joseph Soloveitchik and most American kashrut organizations, others decisors, like Rabbi Yosef, rejected this dispensation, asserting that the prohibition required definitive Jewish supervision (Yechaveh Da’at 4:42). Some raised further fears that this would lead to the neglect of the law in contemporary locales with neglectful inspectors or where nonkosher milk is readily available, such as in parts of Eastern Europe (Helkat Ya’acov 3:37).
When available, Rabbi Feinstein himself advocated using supervised milk, which has become increasingly prevalent in Diaspora communities.
Given the preponderance of dairies within Israel, the Israeli Chief Rabbinate (Tehumin 23) does not accept this leniency and requires Jewish supervision at all factories, even as it reluctantly accepts the more moderate dispensation of Rabbi Frank (Har Tzvi YD 103-4) for powdered milk. American dairy products imported into Israel, however, frequently rely on this lenient opinion, and therefore bear on their Hebrew label that they are kosher only according to certain standards.
The writer, online editor of Tradition and its blog, Text & Texture (, teaches at Yeshivat Hakotel.