Fall 2025<\/p>\n\n\n\n
[This is an expanded version of the article that appeared in the Fall 2025 print issue of Kashrus Kurrents<\/em>.]<\/p>\n\n\n\n Basar b\u2019cholov<\/em> \u2013 the Torah\u2019s prohibition against mixtures of meat and milk and its Rabbinic guardrails \u2013 constitutes one of the most fundamental laws of kashrus. Repeated thrice in the Torah, the posuk<\/em> of lo sevasheil g\u2019di bachaleiv eemo<\/em>[1]<\/a> \u2013<\/em> do not cook a young goat in its mother\u2019s milk \u2013 proscribes three distinct actions: (1) cooking meat with milk (bishul<\/em>);[2]<\/a> (2) eating the mixture (achilah<\/em>); and (3) deriving benefit from the mixture (hana\u2019ah<\/em>).<\/p>\n\n\n\n Conventionally, milk<\/em> is defined as the mammary gland secretion of a lactating mammal. This definition usually aligns with the halachic parameters of what\u2019s considered milchig<\/em> for purposes of keeping it separate from meat in a kosher kitchen. But is that always so? Can milk sometimes be pareve<\/em>?[3]<\/a><\/p>\n\n\n\n Certainly, the whitish, liquid derivatives of beans and nuts \u2013 called \u201cmilk\u201d using borrowed terminology \u2013 are pareve<\/em>.[4]<\/a> Resembling actual milk, plant-based milks may be subject to halachic restrictions due to maris ayin<\/em>.[5]<\/a>Moreover, they are commonly processed on equipment shared with dairy, which may compromise their pareve<\/em> status.<\/p>\n\n\n\n But how about mammalian milks? Are they ever conferred a pareve<\/em> designation?<\/p>\n\n\n\n Despite the reference in the posuk<\/em> to a g\u2019di<\/em>, a young goat, Chazal determined that the prohibition encompasses the meat of all kosher beheimos<\/em> \u2013 cattle, sheep and goats \u2013 regardless of age. Furthermore, despite the possessive form eemo<\/em> \u2013 referencing the animal\u2019s own mother \u2013 basar b\u2019cholov<\/em> precludes cooking meat in the milk of any kosher beheimah<\/em> \u2013 and even in the animal\u2019s own milk.[6]<\/a><\/p>\n\n\n\n Nevertheless, since the possessive eemo<\/em> suggests a degree of equivalence between the sources of meat and milk, Chazal deem some cases of milk to be excluded from the prohibition, at least on a d\u2019Oraysa<\/em> level:<\/p>\n\n\n\n \u25ba Non-Kosher Animals<\/strong> \u2013 Milk from a non-kosher animal is not kosher \u2013 hayotzei min hatamei tamei<\/em>. When non-kosher milk is cooked with kosher meat (e.g., camel milk and flanken) and imparts taste, the meat, too, becomes non-kosher due to absorption.<\/p>\n\n\n\n But does the mixture become basar b\u2019cholov<\/em>? The answer is no<\/em>. Just as g\u2019di<\/em> by definition connotes a kosher animal,<\/em> eemo<\/em> \u2013 itsmother \u2013 likewise alludes to milk derived from a kosher animal. Since milk of a non-kosher animal cannot create basar b\u2019cholov<\/em>, it is permitted to cook even kosher meat with such milk and to derive benefit from the mixture (Y.D. <\/em>87:3).[7]<\/a> Accordingly, one may cook kosher meat with non-kosher milk (or vice-versa, non-kosher meat with kosher milk) on behalf of a non-Jew or to feed a pet, provided one addresses issues of maris ayin<\/em>.<\/p>\n\n\n\n \u25ba Kosher Chayos <\/em><\/strong>\u2013 Meat of a kosher chayah <\/em>(e.g., a deer) does not become basar b\u2019cholov <\/em>(mi\u2019d\u2019Oraysa) <\/em>when cooked with beheimah<\/em> milk (e.g., venison cooked in cow\u2019s milk).[8]<\/a> So too,<\/em> chayah<\/em> milk does not confer a basar b\u2019cholov <\/em>prohibition when cooked with beheimah<\/em> meat (e.g., deer milk cooked with flanken).[9]<\/a> Rabbinically, however, the mixture is<\/em> designated basar b\u2019cholov<\/em>.[10]<\/a> But that is only with respect to achilah<\/em>; bishul<\/em> and hana\u2019ah<\/em> are permitted when done in a manner that avoids maris ayin (Shach <\/em>87:6).<\/em><\/p>\n\n\n\n Another qualification for milk to be considered milchig <\/em>arises from the word eim<\/em> (mother) itself. Liquid milk remaining in the udder of an animal after it is no longer alive \u2013 whether because it underwent a kosher shechita<\/em> or otherwise died and became a neveilah<\/em> \u2013 is not milchig mi\u2019d\u2019Oraysa<\/em>, since its source is an animal no longer capable of being an eim (Y.D. <\/em>87:6, 90:1).<\/em>[11]<\/a> Mi\u2019derabanan<\/em>, this milk may not be cooked with meat and, if it was, the mixture may not be eaten. Deriving hana\u2019ah<\/em>, however, from this mixture is allowed by many poskim.<\/em>[12]<\/a><\/p>\n\n\n\n This last exclusion of milk taken from a shechted <\/em>animal has ramifications for the milk of a bas pekuah<\/em>. A ben <\/em>or bas pekuah<\/em> is a calf born after its mother underwent a kosher shechitah<\/em>. Halachically, the mother\u2019s shechitah<\/em> is effective for its yet unborn calf and, mi\u2019d\u2019Oraysa<\/em>, the calf may be eaten without any additional shechitah<\/em>, even after it has lived for many years. (As a matter of procedure, on account of maris ayin<\/em>, halachah requires shechita <\/em>for a ben pekuah<\/em> once it walks on the ground, Y.D. <\/em>13:2.) The question is: if a female bas pekuah<\/em> calf grows into a lactating cow, what is the status of its milk?<\/p>\n\n\n\n Shaar HaMelech<\/em> (Izmir, 18th<\/sup> century) and Maharit Algazi (Izmir-Yerushalayim) proposed that mi\u2019d\u2019Oraysa<\/em> the milk of a bas pekuah <\/em>is pareve<\/em> since, after all, it comes from an animal that is halachically classified as a shechutah.<\/em>[13]<\/a> On the other hand,<\/em> the Noda BiYehudah<\/em> rejected this suggestion, arguing there is no categorical exclusion of milk from a shechutah.<\/em>[14]<\/a> Rather, once a cow is shechted,<\/em> any remaining milk is pareve<\/em> because the criterion of eemo<\/em> (coming from a potential mother) is no longer applicable. But a bas pekuah<\/em> is fully capable of being a mother, and thus its milk is unquestionably milchig<\/em>.<\/p>\n\n\n\n Following the position of Shaar HaMelech <\/em>that bas pekuah <\/em>milk is pareve<\/em>, Mitzpeh Ayson <\/em>(commentary to Bechoros <\/em>6b) finds a creative solution to the question of how Avraham Avinu served his guests butter and milk together with meat (Parshas Vayeira<\/em> 18:8). The Midrash (cited in Daas Zekeinim<\/em>) indicates they were served a mixture that, mi\u2019<\/em>d\u2019Oraysa, <\/em>constituted basar b\u2019cholov<\/em>. How could Avraham, who observed all precepts of the Torah before they were formally given (Yoma<\/em> 28b), benefit from basar b\u2019cholov <\/em>by serving it to his guests?[15]<\/a><\/p>\n\n\n\n Furthermore, the Talmud (Bava Metzia <\/em>87a) explains that Avraham removed bread from the menu upon learning it became tamei<\/em>. If he scrupulously abstained from a merely laudatory practice (not serving tamei<\/em> food at a non-consecrated meal to assumed heathens), surely, he would have avoided serving milk and meat together \u2013 an outright prohibition? These difficulties are resolved by asserting that Avraham\u2019s milk source was a bas pekuah<\/em> and was actually pareve<\/em> and not subject to basar b\u2019cholov<\/em>.[16]<\/a> This answer, however, is unsatisfactory according to the Noda BiYehudah,<\/em> who holds that bas pekuah<\/em> milk is in fact milchig<\/em>.<\/p>\n\n\n\n An alternate approach is advanced by Malbim (Parshas Vayeira<\/em> ad loc.). He cites a tradition that Avraham served his guests the meat of a calf he fashioned using the secrets of Sefer Yetzirah<\/em>.[17]<\/a> Its meat is pareve<\/em> because it does not have a mother as a biological precursor. The 19th<\/sup> century dayan,<\/em> Rav Shlomo HaKohen of Vilna, in his glosses to Shulchan Aruch <\/em>(Cheshek Shlomo, Y.D<\/em>. 98, Shach<\/em> 6), applies this ruling also to milk taken from such an animal, and to milk formed directly through Sefer Yetzirah<\/em>. Although identical to cow\u2019s milk, it\u2019s not milchig<\/em>.<\/p>\n\n\n\n No master of Sefer Yetzirah<\/em> would dare exploit its supernal wisdom to fashion \u201cdairy\u2011esque\u201d foods for commercial use. But food manufacturers are actively manipulating microscopic elements in the physical world to produce substances that are nearly chemically identical to dairy derivates. It follows that if artificial milk made through Sefer Yetzirah<\/em> \u2013 which fundamentally shares elemental properties with mammalian milk on the metaphysical plane \u2013 is pareve<\/em>, then certainly, artificial milk made through a physical process with relatively superficial resemblance, should be pareve,<\/em> too.[18]<\/a><\/p>\n\n\n\n Established companies and startups alike are investing heavily in disrupting the dairy industry by putting the cows out to pasture \u2013 quite literally. Since the mid-twentieth century, the composition of cow\u2019s milk, one of the most scientifically studied food items, has been identified as comprising approximately 87% water, 4.9% carbohydrates (primarily lactose), 3.4% fat (depending on the breed and diet), 3.3% proteins, and minerals and vitamins. The protein fraction is about 80% casein (digested slowly) and 20% whey (digested rapidly). Various enzymes are a small but important part of the proteins, as well.<\/p>\n\n\n\n It should theoretically be feasible to synthesize this profile in a lab. Water is water. The minerals and vitamins can be gleaned from other natural sources. Plant sugars are not exactly the same as lactose but are a good enough substitute (and superior for those suffering from lactose intolerance[19]<\/a>). That leaves less than 7% of the entire formulation \u2013 the fats and proteins \u2013 as uniquely \u201cmilk.\u201d<\/p>\n\n\n\n Reproducing the full taste, mouthfeel, and nutritional profile of milk is not yet achievable. Milkfat is incredibly difficult to replicate since it is composed of more than 400 different fatty acids, making it the most complex of all natural fats. Consequently, for now, other sources of fat must suffice. Companies are attempting to synthesize milk proteins (absent their indigenous enzymes) which are ostensibly the components most responsible for providing the primary characteristics of dairy products such as ice cream, yogurt and cheese.<\/p>\n\n\n\n The main method for commercial production of lab-grown casein and whey is through precision fermentation<\/em>. To understand this process, let\u2019s first review examples of what occurs in regular, natural<\/em> fermentation:<\/p>\n\n\n\n \u25ba<\/strong> Yeast fermentation in winemaking<\/em> \u2013 grape juice is exposed to yeast (a type of fungus, occurring naturally on grape skins or added by the winemaker) which ingests the grape juice sugars and converts them into ethyl alcohol (ethanol) and carbon dioxide (usually released but retained in fizzy varieties), resulting in wine.<\/p>\n\n\n\n \u25ba<\/strong> Yeast fermentation in breadmaking<\/em> \u2013 water added to flour activates enzymes (amylase) that break down grain starch into sugars. Yeast transforms the sugars into CO2 <\/sub> and ethanol (which mostly evaporates during baking). When the gas bubbles are trapped by the grain\u2019s gluten network, the dough rises.<\/p>\n\n\n\n \u25ba<\/strong> Bacterial fermentation<\/em> \u2013 bacteria transform carbohydrates into lactic acid to make foods like cheese, yogurt and sauerkraut.[20]<\/a><\/p>\n\n\n\n The novelty of precision fermentation is that instead of letting nature decide the outcome of the fungal or bacterial conversion, scientists bioengineer fungi to yield a specific target protein of their choosing.<\/p>\n\n\n\n A foundational step in synthesizing milk proteins took place in the 1990s and 2000s when researchers mapped the bovine genome. Once the DNA sequence to produce milk protein genes was identified, the segment could be amplified using technologies like PCR (polymerase chain reaction). Scientists detach snippets of the cloned gene (via enzymes acting as molecular scissors) and introduce them into fungal DNA. This newly encoded recombinant fungus is placed in a bioreactor \u2013 a controlled-environment vessel that facilitates biological processes \u2013 where it acts as a fermentation catalyst to convert sugary, nutrient-rich broth into a resultant mixture containing the target protein.<\/p>\n\n\n\n When fermentation is complete, the target protein is harvested and isolated from the mixture using the same filtering and refining technique already ubiquitous in the dairy industry to isolate whey protein from cow\u2019s milk. The synthesized protein is now ready to contribute dairy-like properties to foods. (How cows automatically generate these complex proteins in their rumens \u2013 all from plain grass \u2013 is truly one of the wonders of Creation!) <\/p>\n\n\n\n While the application of precision fermentation to synthesize dairy proteins is fairly recent, this technology has been widely used on a commercial scale since the early 1980s to manufacture synthetic insulin, replacing the older, resource-intensive process developed in the 1920s for extracting insulin from cow and pig pancreases.<\/p>\n\n\n\n Precision fermentation\u2019s profound impact on the dairy industry actually goes back to 1990, when the FDA approved a bioengineered food ingredient for the first time, allowing chymosin <\/em>(also known as rennin<\/em>) \u2013 the enzyme which coagulates milk into curds when making cheese \u2013 to be produced synthetically through fermentation. From the dawn of cheesemaking, chymosin was sourced from rennet extracted from a nursing calf\u2019s abomasum (fourth stomach compartment).[21]<\/a> That classical method has since been relegated to a small niche market. Within a decade, fermentation-produced chymosin (FPC) became the predominant source of cheese coagulant.[22]<\/a><\/p>\n\n\n\n Synthesized dairy proteins are pareve<\/em> provided all the materials used to synthesize them derived from kosher pareve<\/em> sources. This is unlike current attempts to produce lab-grown meat, which starts with stem cells obtained from animals. According to the psak <\/em>of Rav Moshe Heinemann shlit\u201da<\/em>, the kosher status of such lab-grown meat products follows its starter material and is subsequently either fleishig<\/em> or a neveilah<\/em>.[23]<\/a><\/p>\n\n\n\n Fungi, the living organisms responsible for fermentation, are inherently kosher.[24]<\/a> But as for all fermented foods items, kashrus oversight is needed for the growth media upon which recombinant fungi are propagated and the nutrients they are fed. Moreover, to maintain the very low temperature necessary to keep them alive, the fungal strain is dissolved in glycerin, a kosher-sensitive ingredient, and packed in cryovials. Glycerin is added to prevent the formation of damaging ice crystals, which can rupture cell walls during shipping to production facilities.<\/p>\n\n\n\n At the facility where the fungus-to-protein conversion takes place, the kosher status of bioreactors must be determined in case they were previously used for batches containing non-kosher or dairy components. Finally, the missing fats and enzymes present in natural mammalian milk must be compensated for in final products by adding other kosher-sensitive oils and ingredients.<\/p>\n\n\n\n Some confusion has arisen among consumers about the labeling of foods, like ice cream, where synthetic whey replaces cow-based dairy. Even though the products have no actual dairy content, FDA regulations still require labels to display a dairy allergen warning statement, because the chemical structure of the synthetic version is similar enough to the real thing to potentially trigger an adverse allergic reaction.[25]<\/a> Confusion aside, this concern has no bearing on the pareve<\/em> (or \u201cdairy equipment<\/em>\u201d) designation of the product.<\/p>\n\n\n\n Looking forward, food producers are banking on expanding the range of products made with precision fermentation. They anticipate that other synthetic proteins, mimicking egg whites, seafood, collagen, gelatin, and even meat, will soon join dairy proteins among consumer offerings \u2013 all potentially certifiable as kosher-pareve<\/em>. Nonetheless, even if synthesized proteins replace natural sources, their kosher certification must remain genuine.<\/p>\n\n\n\n [1]<\/a> Mishpatim<\/em> 23:19, Ki Sisa<\/em> 34:26, Re\u2019ei<\/em> 14:21. <\/p>\n\n\n\n [2]<\/a>Poskim<\/em> (Y.D.<\/em> 87:1) dispute whether the Torah\u2019s prohibition of bishul basar b\u2019cholov <\/em>is limited to cooking in a liquid medium or if it includes other processes involving a fire-based heat source \u2013 i.e., roasting and frying. If those are just a Rabbinic prohibition, then only bishul<\/em> and achilah<\/em> are prohibited but hana\u2019ah<\/em> is permitted.<\/p>\n\n\n\n [3]<\/a> The word pareve<\/em> belongs to a small set of Yiddish words of Slavic origin. Related to the Polish word para<\/em>, meaning \u201cpair,\u201d pareve<\/em> signifies a food that is halachically pairable with either milk or meat.<\/p>\n\n\n\n [4]<\/a> Cholov sh\u2019keidim<\/em>, almond milk, mentioned by Rama (Y.D<\/em>. 87:3), was a widespread beverage and food ingredient in Europe already in the late Middle Ages.<\/p>\n\n\n\n [5]<\/a> Rama 87:3. See \u201cOptical Allusions: Avoiding Maris Ayin<\/em><\/a>,\u201d by Rabbi Chananya Jacobson, Kashrus Kurrents<\/em>, Fall 5782\/2021.<\/p>\n\n\n\n [6]<\/a> Shulchan Aruch Y.D<\/em>. 87:2 and Pri Chadash<\/em>.<\/p>\n\n\n\n [7]<\/a> Since cooking kosher meat with non-kosher milk (or kosher milk with non-kosher meat) does not designate the mixture as basar b\u2019cholov, <\/em>certain leniencies with respect to bitul<\/em>, nullification, will apply: (1) The Mechaber (Y.D. <\/em>92:4) holds \u2013 unlike Rama – that chatichah na\u2019aseh neveilah <\/em>(chana\u201dn<\/em>) is only for items prohibited due to basar b\u2019cholov<\/em> and not for other prohibited mixtures or absorptions. Therefore, according to Mechaber, bitul <\/em>would be achieved with just 60x the absorbed milk and not 60x the entire piece. (2) The stringency of chatichah ha\u2019re\u2019uyah le\u2019hiskabeid, <\/em>preventing bitul<\/em> of respectable cuts of meat, is only for pieces classified as intrinsically prohibited (e.g., neveilah<\/em> or basar b\u2019cholov<\/em>) but not for pieces that are prohibited due to absorption.<\/p>\n\n\n\n [8]<\/a> Ten types of kosher animals are listed in the Torah: three are beheimos <\/em>and seven are chayos<\/em>. Netziv <\/em>(Ha\u2019emek Davar, Bereishis <\/em>1:24) asserts the distinction between chayos <\/em>and beheimos<\/em> is that beheimos<\/em> have a predisposition to being domesticated while chayos <\/em>are naturally wild. He challenges the Ramban\u2019s position that their classification is determined by diet.<\/p>\n\n\n\n [9]<\/a> Following Y.D. <\/em>87:3, Shach<\/em> (4) and Pischei Teshuvah<\/em> (4).<\/p>\n\n\n\nExegetical Expansions and Exceptions<\/h3>\n\n\n\n
Milk of a Bas Pekuah<\/em><\/h3>\n\n\n\n
Milk of Metaphysical Matter<\/h3>\n\n\n\n
Milk: Deconstructed and Reconstructed<\/h3>\n\n\n\n
Precision Fermentation: Synthesizing Dairy Proteins<\/h3>\n\n\n\n
Kashrus Considerations<\/h3>\n\n\n\n
Final Ruminations<\/h3>\n\n\n\n
\n\n\n\n