What is the whole issue of eating cheese that is “kosher”? One set of opinions I read says that most processed cheese is not kosher, and another set of opinions says most processed cheese is just fine.
Curdling animal milk to make cheese is one of the oldest practices in human culinary history, and was something certainly found in the Ancient Near Eastern diet of Ancient Israel, as well as the Mediterranean diet of Second Temple Judaism and its Diaspora. While cheeses have been produced by the Jewish community for centuries, the issue of procuring cheese from a non-Jewish source, which may have been produced using the milk, or some other byproduct, of a non-kosher animal, has seen to the issuance of many Rabbinic directives. In the more modern period, especially in North America with its agriculture highly regulated, the issue of rennet for cheese production, introducing the rennin enzyme for the coagulation of the milk, is debated within the Jewish community. On the whole, Orthodox Jews will only eat certified-kosher cheese which has been produced entirely under Rabbinic supervision. Conservative Jews, on the other hand, are generally prone to consider all commercially-produced cheeses as being kosher.
Yacov Lipschutz, author of the Kashruth volume by the Orthodox Jewish publishing house ArtScroll, summarizes the basic Orthodox position on cheese production:
“Cheese is produced naturally by coagulating milk. This coagulation is caused by the addition of milk of the mucosa found in the stomach linings of calves. Where cheese is produced by non-Jews there is an assumption that the stomach linings used were non-kosher, and the cheese is therefore forbidden. The prohibition described in the Mishnah…includes all cheese manufactured by non-Jews, even if all the ingredients of the cheese are kosher. Only cheese of Jewish production, or overseen by observant Jews, is permissible, provided the rennin coagulant used is kosher-produced from the linings of kosher-slaughtered, properly prepared and dried calf stomachs. Included in this restriction are all hard cheeses, e.g., Swiss, Cheddar, Muenster, Mozzarella, Gouda, Colby, Salud, etc.
“This method of production is similar to cheese production in modern times; however, instead of using the stomach lining itself to coagulate the milk, extracts of the lining which contain the rennin enzyme are processed, and used in cheese and other dairy products. The forbidden extract containing the rennin enzyme is called rennet…Rennet substitutes have been developed by microbial means, and milk-clotting enzymes for cheese making are produced from fungi. These microbial enzymes are sometimes referred to as ‘microbial rennet,’ though rennet is a technical term used solely for the enzyme derived from the stomach linings of calves.”
Samuel H. Dresner summarizes the basic Conservative Jewish position, in the 1982 publication The Jewish Dietary Laws:
“All milk and dairy products, including cheese, are kosher and do not require rabbinical supervision.
“This was not always the case. In ancient days, it was possible to adulterate milk with animal fats. Milk also might have come from nonkosher animals. Thus, it was customary to use only dairy products produced under rabbinical supervision. Under modern conditions, however, including government inspection, most authorities agree that there is no longer need for such supervision.
“The status of cheese was the subject of controversy beginning in ancient times, and even today some people eat only cheese that has been rabbinically certified. The point at issue: Is rennet, a substance derived from an animal and used in cheesemaking, actually a meat product or even a food? Conservative authorities, and others, on the basis of extensive study of the subject, have concluded that rennet is not a food product, and thus no rabbinic supervision is needed.”
Sue Fishkoff reports how much of the process of making hard cheeses has been streamlined by Orthodox Jews, in her book Kosher Nation:
“Making hard cheese requires full-time kosher supervision. The process utilizes rennet, an enzyme that comes from the stomach lining of calves. Although most kosher agencies hold that rennet is so far removed from the actual cow that it is not in itself considered food, and virtually all rennet used in the United States is now vegetable based, the process is still carefully monitored. Only an observant Jew is permitted to add the rennet during the cheesemaking operation. In old-fashioned factories, this is done by hand—the mashgiach pours in the bucket of rennet whenever the coagulation stage is reached. In most modern plants the process is automated, but kosher certification agencies still require that a mashgiach press the activation button that sends the rennet through the system.”
There has not been a huge amount of contemporary Messianic discussion about the issue of cheese, but among that which has been printed and widely disseminated, there has been a tendency to lean toward an Orthodox Jewish approach to cheesemaking. The following summary is witnessed in the 2012 book Biblically Kosher by Aaron Eby:
“Cheese is another great example of a product that would seem perfectly kosher, but could very well pose a problem. Of course, added flavors, colors, anti-caking agents, preservatives, and additives that modify the texture of the cheese raise concerns. However, an essential ingredient in cheese is the complex of enzymes known as rennet, which is added in order to coagulate the milk. Rennet is traditionally derived from the stomach lining of calves, but pig enzymes can also be used….
“Fortunately, porcine (that is, pig) pepsin is becoming less common. Instead more cheese producers use microbial sources for the rennet, which could alleviate some kashrut concerns.
“Jewish law does not consider animal rennet in milk to be a forbidden combination of meat and dairy. However, since the rennet comes from an animal’s stomach, the animal must be a kosher species. Furthermore, it must be slaughtered in a kosher manner. This requirement would disqualify any cheese containing animal rennet from a source that is not specifically kosher. If the cheese producer uses exclusively microbial rennet, these concerns would be also alleviated.
“Beyond these biblical concerns, there is an additional overarching safeguard required by rabbinic law: Cheese produced by non-Jews is forbidden [m.Avodah Zarah 2:5]. The specific reason for this is not explained in the Mishnah, but the Gemara [b.Avodah Zarah 29b, 35a-b] posits some theories, including health issues, contamination from non-kosher food, and association with idolatry. This requires that an observant Jew be present at the facility to supervise and possibly to activate some of the equipment. Consequently, this also limits the ability of the plant to operate on the Sabbath.
“Some kashrut agencies (such as the Orthodox Union) feel that this prohibition only applies to solid cheeses that are coagulated with rennet (microbial or otherwise), but soft cheeses that are coagulated with acid are acceptable without direct Jewish involvement. This is why cream cheese, cottage cheese, and some kinds of mozzarella are often certified kosher without a substantially higher price.”
Many of today’s Messianic people, Jewish or non-Jewish, are not too familiar with the issues of cheese production, and the debates over rennet between Orthodox and Conservative Jewish authorities. Given the fact that most kosher-friendly Messianic people are prone to only keep a kosher-style diet, mainly avoiding pork and shellfish, and with that eating a wide variety of commercially-processed meats—they would similarly be most likely to accept the mainstream Conservative Jewish view on cheese production, which has ruled that most rennet used in cheesemaking is acceptable for Conservative Jews to eat. As is summarized in Isaac Klein’s 1979 work, A Guide to Jewish Religious Practice,
“The controversy over the kashrut of cheeses is an old one, dating back to the time of the Talmud (m. A.Z. 2:4, 5; M. Ḥul 8:5; b. Ḥul. 116b). Cheese is made from curdled milk. Since the curdling agent was rennet, which is extracted from the walls of a calf’s stomach, cheese was forbidden as a mixture of dairy and meat. According to some authorities, however, the use of rennet does not affect the kashrut of cheese because rennet no longer has the status of food and instead is comparable to a mere secretion ([pir’sha b’al’ma]). This controversy appears again and again among the posqim (see Rabbenu Tam in B. A.Z. 35a, s.v. [chda qtny]; Maimonides, Hil. Ma’akhalot ‘Asurot 4:13, 14, 19; ‘Arukh Hashulḥan, Y.D. 87:42). Some halakhic authorities demand a hekhsher for certain cheeses, implying that those without a hekhsher are not kosher; other authorities maintain that all cheeses are permissible and no hekhsher is necessary.
“The Committee on Law and Standards of the Rabbinical Assembly has decided to follow the lenient option. First of all, it reasons the [chash’shot] (fears) expressed by those who require a hekhsher applied only in former times, when cheesemaking was a cottage industry and there was no way to control the ingredients used. Under these conditions, there was always the danger that an individual farmer who made cheese might use the milk of a nonkosher animal or might add lard to the mixture. Today however, at least in America, cheesemaking is a major industrial enterprise regulated by the Pure Food and Drug Law, which requires that most food products bear a label listing their ingredients.
“Furthermore, the rennet used in many of the hard cheeses does not impair their kashrut, both for the talmudic reason stated above and also because the substance from which the rennet is extracted is thoroughly dried and treated with strong chemicals, and this process makes the rennet a [chadash davar] (new substance) or comparable to a piece of wood ([etz b’al’ma]). Thus, all cheeses that are subject to the Pure Food and Drug Act should be considered kosher…”
 Yacov Lipschutz, Kashruth: A comprehensive background and reference guide to the principles of Kashruth (Brooklyn: Mesorah Publications, Ltd, 1989), pp 56-57.
 Samuel H. Dresner, The Jewish Dietary Laws: Their Meaning for Our Time (New York: The Rabbinical Assembly of America, 1982), pp 64-65.
 Sue Fishkoff, Kosher Nation: Why More and More of America’s Food Answers to a Higher Authority (New York: Schoken Books, 2010), 83.
 Aaron Eby, Biblically Kosher: A Messianic Jewish Perspective on Kashrut (Marshfield, MO: First Fruits of Zion, 2012), pp 125-126.
 Isaac Klein, A Guide to Jewish Religious Practice (New York: The Jewish Theological Seminary of America, 1979), 306.