Gelatin is a substance usually made from animal parts, notably bones and ligaments, but also the skins. These parts are processed to release the collagen in them, and gelatin is derived from that. Gelatin is used for foods such as molded gelatin desserts and marshmallows, to make capsules for medicine, and to clarify wine and beer and for food preservation. Kosher gelatin is the same as all other gelatin, except that the source of the collagen must be kosher.
Gelatin was originally made by boiling calves’ feet in huge kettles for hours. Eventually the liquid was strained off and the bones and hooves were discarded. The resulting liquid would sit for 24 hours, after which time a layer of fat would have risen to the top. This fat would be skimmed off and thrown away, and then flavoring and sweetener would be added to the liquid. Finally, the gelatin was poured into bowls or molds and allowed to set before serving.
In the mid-1800s, Charles Knox, along with others, began to prepare and sell sheets of dried gelatin. They taught housewives how to use these to prepare gelatin dishes, instead of having to go through the entire preparation process themselves. The idea caught on and Knox’s wife published a recipe book for gelatin shortly before the end of the century.
At the time, there was not much concern with making kosher gelatin commercially. Although Knox and others had some success with the sales and marketing of plain gelatin, those who wanted to ensure their food was kosher did not have a ready commercial source of the product. Women continued to make kosher gelatin at home, by the same laborious process that had been used for many years.
The essential difference between kosher gelatin and all other gelatin is that the kosher gelatin must be made from kosher sources. There cannot be any so-called unclean animals or parts from animals not butchered according to kosher law in the gelatin. Making kosher gelatin uses essentially the same process as has been used for hundreds of years, with some modern updates, but only kosher ingredients are involved.
In the 21st century, kosher gelatin is readily available from commercial sources. Different manufacturers use different sources for the collagen that is the basis for the gelatin. They may use deep sea fish, cattle or plant-based collagen, all of which are kosher. Which type of kosher gelatin is used is largely a personal preference. The most important thing for Jewish people wishing to eat only kosher products is that the gelatin must be labeled as kosher, because if it doesn’t say it on the package, no matter which collagens were used, it isn’t kosher.