Summer 2025

From fruit-on-the-bottom yogurt cups to your Bubby’s famous galarita (a.k.a. p’tcha), collagen – and its modified form, gelatin – seems to be everywhere these days. It is no exaggeration to state that the food and health industries are currently undergoing a veritable collagen craze. In 2023, the collagen market had a value of $5.1 billion, with no signs of slowing down; it is projected to top $7.4 billion by 2030.[1] What exactly is collagen and why is it so popular?

Collagen is a fibrous, insoluble protein found in all living beings. The word collagen comes from the Greek word kolla, meaning glue, which is a fitting term for a substance that makes up a major portion of bone, skin and connective tissue and serves as the glue that holds the body together. There are three main types: type I, found in skin, tendons, bones and ligaments; type II, found in cartilage; and type III, found in skin, muscles and blood vessels.

Cooking the bones helps to release the collagen in them and to thicken the cooking liquid. That is the basic recipe for p’tcha, and it also explains why you may find jarred gefilte fish suspended in a wobbly jelly.[2] But commercially produced collagen for industrial use is a more complex process.

The Widespread Utility of Gelatin

The collagen in animal bones, hides and cartilage are typically extracted through enzymatic or acid/alkali hydrolysis, and then purified and dried. Gelatin is a partially hydrolyzed form of collagen. The word gelatin is derived from the Latin word gelatus, meaning stiff or frozen; its stiffness is measured in units called bloom, a term credited to its inventor, Oscar T. Bloom. Different applications require different bloom levels. For example, high bloom refers to a high molecular weight, and gelatin with high bloom has a stiffer consistency.

Gelatin is a popular additive in foods because it is fat-free yet offers a smooth “mouth feel” that is similar to fat, making it ideal for use in products like low-fat ice cream and yogurt. Gelatin also acts as an emulsifier, which helps to distribute fat and add stability to confections and products like spreadable frosting, ice cream, toffee and yogurt. The addition of gelatin can extend the shelf life of candy because it does not break down as quickly as sugar, making it ideal for throat lozenges, gel desserts and Gummy Bears. Similarly, hard sugar glazes will stay white and not run when gelatin is added. When aerated, gelatin retains its shape to create light and fluffy marshmallows.

In vitamins and medicines, gelatin is used to coat tablets to mask a bitter taste and to produce gelcaps to house powdered medicines. Health-conscious consumers may use plain gelatin as a protein supplement.

Halachic Considerations of Collagen and Gelatin

Clearly, gelatin is an industrial marvel and an incredibly useful ingredient in the manufacture of many processed foods and confections. But the kosher consumer faces a dilemma when encountering foods containing gelatin, since most gelatin is made from animal products derived from non-kosher or non-kosher-slaughtered animals.

As mentioned earlier, gelatin is made by extracting collagen from the bones and skins of animals, and the skins or scales of fish. There are several questions that must be addressed in order to understand the halachic status of gelatin.

According to halacha, the meat of animals or fish designated as tamei (i.e., from a non-kosher species), such as pigs, horses, catfish and shark, may not be consumed. So, too, the meat of an animal that is tahor (i.e., from a kosher species) but was not slaughtered according to the laws of shechita is a nevela and also prohibited.

Knowing these laws, a host of questions arise:

1. Do these prohibitions also apply to the bones and hides of the animal?
2. If the prohibitions of nevela and tamei were to apply to the skins and bones, can their status be altered through the process used to manufacture gelatin?
3. If the animal source for the gelatin is kosher, does the gelatin retain the properties inherent to its source? Namely, is such gelatin considered a meat product when sourced from an animal, rendering it forbidden to be cooked with milk or, if fish-sourced, can it be cooked with meat?

Let’s briefly address these questions one-by-one and see what our poskim have to say.

(1) Kosher Status of Animal Hides and Bones

The question of whether or not the bones of a non-kosher animal carry the same prohibition as the meat is discussed by Chazal.[3] The Shulchan Aruch maintains that the bones of a prohibited animal are kosher and count as part of the permitted food in constituting a majority of sixty kosher parts. The Rema concurs that the bones are not prohibited but holds that they do not count as part of the kosher percentage when mixed with other kosher food.

On the other hand, the Shach distinguishes between bones that retain some moisture and those that are totally desiccated. He holds that bones of non-kosher animals that retain any fluids are not kosher; only dry bones are accepted as kosher. According to some rabbinic authorities, collagen is contained within the natural liquid of bones, which the Shach prohibits.

It is worth noting that the Shulchan Aruch refers only to the actual bone and not to the bone marrow, which is considered to be meat. Furthermore, kosher bones processed with non-kosher meat or bone marrow are rendered non-kosher.

The halacha according to the poskim is clear: in order to produce gelatin from a non-kosher animal bone, the bone must be cleaned and dried and contain no marrow or soft tissue. Gelatin manufacturers would need to strictly adhere to these requirements. We cannot assume that their manufacturing process is sufficient to produce a gelatin which rabbinic authorities would consider kosher. Then, too, there is the Shach’s opinion that the collagen in the bone is prohibited as part of the animal’s fluids. For all of these reasons, most reputable kosher certifying agencies prohibit the consumption of gelatin from a non-kosher animal.

Even sourcing gelatin from a kosher animal poses logistical problems. Aside from the prohibitions of tamei and nevela, as previously noted, we are concerned with the prohibition of treifa – the Torah’s prohibition of consuming animals that possess certain injuries or disorders. Since most inspections conducted to determine if the animal is treifa occur after the slaughter and skinning of the animal, the hides must be tracked to ensure that treifa hides are not mixed with kosher hides. For this reason, gelatin productions require meticulous supervision.

Finally, as with any kosher food, gelatin must be produced on kosher equipment. When the processing is done in a non-kosher plant (as is usually the case), the equipment must be thoroughly cleaned and kosherized before the production can begin.

(2) Effect of Processing on the Status of Meat

In reference to the question as to whether or not the processing alters the status of the meat, we may cite a similar question discussed in the Gemara.[4] It used to be a common practice to make cheese curd by adding the skin of a calf’s stomach to milk,[5] or by letting the milk sit in a calf’s stomach. According to the Rema, the cheese was permitted only if the stomach had been salted and dried so that it resembled a piece of wood before the milk was added. The Shach cautions that although one may use such milk products, it is not proper to do this l’chatchila.

The Pri Megadim qualifies the Rema’s leniency by noting that his psak applies specifically to the stomach of an animal, which contains less meat flavor. He adds that the Rema allowed this only when the stomach was removed from the milk within 24 hours and was not heated with the milk. If the stomach stays for a period of over 24 hours, or if it is heated with the milk, it would absorb the meat flavor which would render it forbidden for use.

These statements were made in reference to dried kosher meat parts which did not carry other prohibitions. The fact that they were dried prevented them from attaining a prohibited status when mixed with milk. This may not be the case when the source is not kosher. There is a rule that states, “that which comes out of a non-kosher source remains non-kosher.” If so, the by-products of a non-kosher animal retain their non-kosher status, and processing does not change that status.

(3) Relationship of Gelatin to Its Source

As to the question regarding whether hides are considered to be meat, Rav Moshe Feinstein zt”l addressed this issue in Igros Moshe,[6] where he writes that according to Torah law, the hides are not considered to be meat but according to rabbinic law, they are prohibited to be cooked with milk.

If the hides are dried and processed, however, the resulting gelatin is not included in this rabbinic prohibition. Therefore, gelatin produced from kosher-slaughtered animal hides may be intentionally used with milk. This ruling would only apply to hides that were cleaned to remove any meat residue. Some poskim disagree with Rav Moshe’s conclusion, most notably Rav Aharon Kotler zt”l, who concludes that gelatin produced from kosher hides is considered to be a meat product.

There is room for leniency, however, when dealing with products that contain gelatin sourced from kosher hides, as gelatin has little or no taste. When mixed with other pareve ingredients, the gelatin is nullified, which would result in a pareve product.[7] Gelatin from non-kosher hides, however, retains its forbidden status.

We have not addressed the question of blood in or on the hides. We know that blood is prohibited for consumption by Torah law – this is why we salt our meats prior to cooking. There is a question about the potential presence of blood that may be absorbed in the hides, which would need to be removed. To satisfy all opinions, kosher hides must be salted prior to processing.

With regards to fish gelatin, the source material must be from a kosher species. The use of fish gelatin with meat foods poses an interesting question. The Shulchan Aruch prohibits the cooking of meat and fish together due to health concerns.[8]

Does gelatin extracted from fish carry this restriction? We tend to be more stringent when dealing with possible health issues than with concerns of issur (prohibited substances). Therefore, there is a question among the commentaries as to whether or not the rule of batel b’shishim (one-in-sixty nullification) applies to unhealthy substances as it does with prohibited substances.

There are many reasons for leniency in the use of fish gelatin together with meat. Many rabbinic authorities hold that the nature of foods in our times may have changed, thus rendering the mixture of meat and fish no longer unhealthy.[9]

Furthermore, there is an opinion that not all fish would be considered a sakana when mixed with meat. It may be that only binita, the species mentioned in the Gemara, is unhealthy.[10] It may also be posited that the unhealthy aspects of fish cooked with meat are only found in the flesh. Since gelatin is made from the skins and/or the scales, it may not have fish flavor and may nor harbor the harmful effects of fish.[11]

With this same reasoning, we can say that fish gelatin can be batel (nullified) with a majority of other food ingredients and can be eaten with meat. For these reasons, some authorities allow the use of products containing fish gelatin with meat; therefore, they also allow products containing animal gelatin to be served with fish. Harav Moshe Heinemann shlit”a, however, is stringent and holds that one should not eat meat together with items made with fish gelatin, such as marshmallows.

The Bottom Line

Gelatin produced from a tahor species of animals or fish, which was properly processed – kosher slaughtered, internally checked (and, in the case of an animal source, salted) and produced using kosher equipment – may be used by the kosher consumer.

---

[1] See https://www.marketsandmarkets.com/Market-Reports/collagen-market-220005202.html.

[2] Note that the use of gelatin in commercial gefilte fish has given way to gelatin substitutes, such as carrageenan (see sidebar, “Gelatin Substitutes”).

[3] Y.D. 99:1.

[4] Y.D. 87:10.

[5] i.e., from a kosher-slaughtered, non-treifah animal.

[6] Y.D. 1:37.

[7] This does not contradict the rule, ein m’vatlin issur lechatchila, as it is a dilution of permitted foods.

[8] Y.D. 116:2.

[9] See Magen Avrohom O.C. 173:1, Teshuvos Chasam Sofer 1:101.

[10] See Pische Teshuvah, Y.D. 116:3.

[11] see Pische Teshuva, Tshuvos Sride Eish 2:67, re: cooking beef in fish oil.