Gelatin (also gelatine) is a translucent brittle solid, colorless or slightly yellow, nearly tasteless and odorless, that is created by prolonged boiling of animal connective tissue.
It is a protein product derived through partial hydrolysis of the collagen extracted from skin, bones, cartilage, ligaments, etc. The natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily. Gelatin melts when heated, and solidifies when cooled again. Together with water it forms a semi-solid colloidal gel.
On a commercial scale, gelatin is made from by-products of the meat and leather industry, mainly pork skins, pork and cattle bones, or split cattle hides. Contrary to popular belief, horns and hooves are not commonly used. The raw materials are prepared by different curing, acid, and alkali processes, sometimes over many weeks, to extract the dried collagen hydrolysate. The worldwide production amounts to 250,000 tons per year.
Household gelatin comes in the form of sheets, granules, or powder. Instant types can be added to the food as is, others need to be soaked in water beforehand. Special kinds of gelatin are made only from kosher animals, or from fish, to comply with Jewish kashrut laws. Vegetarians may substitute similar jellying agents such as agar, sometimes incorrectly referred to as "vegetable gelatins". There is no chemical relationship, and gelatin cannot be derived from vegetable sources. The name is colloquially applied to all types of gels and jellies, but in the legal sense 'gelatin' only refers to the animal protein product.
Due to the mad cow disease (BSE) and its link to the Creutzfeldt-Jakob disease, there has been much concern about using gelatin derived from possibly infected animal parts. A study released in 2004, however, demostrated that the gelatin production process destroys most of the BSE prions that may have be present in the raw material.
Probably best known from cooking as a jellying agent, different types and grades of gelatin are used in a wide range of food and non-food products:
Common examples of foods that contain gelatin are trifles, jelly, aspic, marshmallows, peeps, or gummy bears. Gelatin may be used as a stabilizer, thickener, or texturizer in foods like ice cream, yoghurt, cream cheese, margarine, etc. — most importantly in fat-reduced foods to simulate the mouth feel of fat, and to create a volume without the calories.
Gelatin sometimes makes up the shells of pharmaceutical capsules in order to make them easier to swallow. It can be used as carrier, coating, or separating agent for other substances, making beta-carotene water-soluble for example which gives a yellow color to many soft drinks. Cosmetics may contain a non-gelling variant of gelatin under the name of "hydrolyzed collagen". Gelatin is closely related to bone glue, and is used as a binder in match heads and sandpaper. As a surface sizing it smoothes glossy printing papers or playing cards, and it keeps the wrinkles in crepe paper.
It is used to hold silver halide crystals in an emulsion in virtually all photographic films and photographic papers. Despite some efforts, no suitable substitutes with the stability and low cost of gelatin have been found.
Gelatin is used for the clarification of juices and beverages such as apple juice or vinegar. Isinglass, from the swim bladders of fish, is still in use as a fining agent for wine and beer. Beside hartshorn jelly, from deer antlers, it was one of the oldest sources of gelatin.
Gelatin is used by synchronized swimmers to hold their hair in place during their routines as it will not dissolve in the cold water of the pool. It is frequently referred to a "knoxing", a reference to Knox brand gelatin. Though common usage, the owners of the trademark object to the genericized use of the term.
See also: gelatin dessert