Kosher foods are those that conform to certain Jewish dietary laws having to do with both the type of food and how it is prepared. Any food that is labeled kosher must conform to these laws. Jell-O® brand gelatin desserts are not made using kosher ingredients, and so there is actually no kosher Jell-O®. There are, however, other gelatin products that are made according to kosher law, and these are certified by rabbis as being kosher foods.
It is not uncommon for people to think that something as simple as Jell-O® is bound to be kosher, since it does not contain any kind of meat. However, though it can be made from plant products, most of the time gelatin is made from animal bones and hides, which contain collagen, the substance that is the basis of gelatin. If the animals used as the source of collagen are not kosher, the gelatin is not kosher. Kosher Jell-O® does not exist because the gelatin base is not made with kosher ingredients.
Originally, gelatin was made in the home. Women had to boil calves hooves and bones for hours, then let the liquid stand for about 24 hours. Once the liquid cooled, fat would rise to the surface and was skimmed and discarded. The remaining liquid was strained, then mixed with sweeteners and flavorings, and allowed to set to create a gelatin dessert. Around the mid-1800s, gelatin began to be made commercially, and by the early 1900s Jell-O® had gained popularity throughout much of the United States and Canada.
Because Jello-O® is made by rendering animal bones and hides without regard to the kosher status of the ingredients, there cannot be any kosher Jell-O®. The other companies that make gelatin products that are certified as kosher are careful to use only kosher ingredients. Many of these gelatins are made with plant-based products, eliminating any concern about whether they are kosher, since all types of plants are acceptable under kosher law. Others are made from only kosher meat-based ingredients and never include pig by-products or parts from other non-kosher animals, creating kosher gelatins similar in taste and texture to other products on the market, but without the possibility that they might include unacceptable ingredients.
Some boxes of Jell-O® have a small “k” on them, with a circle around it, leading many people to believe that it is kosher Jell-O®. The logic behind this appears to be that, even though the product includes pork bones and hides, these do not constitute meat and are therefore not unclean. Also, some argue that the chemicals used to process the collagen change it enough that it is acceptable under kosher law. Not everybody agrees that such processing creates kosher Jell-O®, so for those people wanting a truly kosher product it is best to purchase products that are certified as kosher, thus eliminating any possible doubt.