Science Fair Project Encyclopedia
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 commercial scales, 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 as 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 certain animals or from fish, to comply with Jewish kashrut or Muslim halal laws. Vegetarians and vegans may substitute similar jellying agents such as agar or pectin, sometimes incorrectly referred to as "vegetable gelatins". There is no chemical relationship, agar and pectin are carbohydrates, not proteins. The name 'gelatin' is colloquially applied to all types of gels and jellies, but in the legal sense, it only refers to the animal protein product. There is no vegetable source for gelatin.
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 gelatin desserts or jelly, trifles, 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 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 typically makes up the shells of pharmaceutical capsules in order to make their contents easier to swallow.
- 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.
- 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.
- Gelatin is closely related to bone glue, and is used as a binder in match heads and sandpaper.
- Cosmetics may contain a non-gelling variant of gelatin under the name of "hydrolyzed collagen".
- As a surface sizing it smoothes glossy printing papers or playing cards, and it keeps the wrinkles in crepe paper.
- Blocks of ballistic gelatin simulate human tissue as a standardized shooting target for testing firearms and ammunition.
- 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 as "knoxing", a reference to Knox brand gelatin. Though common usage, the owners of the trademark object to the genericized use of the term.
For decades, gelatin has been touted as a good source of protein. It has also been said to strengthen nails and hair. However, there is little scientific evidence and health claims are suggestive and vague. Much can be attributed to Knox's revolutionary marketing techniques since back in the 1890s, when it was advertised that gelatin contains protein, and lack of protein causes dry, deformed nails.—The human body already produces abundant amounts of the proteins which gelatin can provide to, and dry nails are usually due to a lack of moisture, not protein.
Although gelatin is 98–99% protein by dry weight, the body cannot readily use it. Gelatin is not nutritionally complete and is notable for its exceptionally low nutritional value. It is unusually high in non-essential glycine and proline, but lacks certain essential amino acids and is one of the few foods that cause a net loss of protein if eaten exclusively. It contains no tryptophan and is deficient in isoleucine, threonine, and methionine. Several people died of malnutrition in the 1970s while on popular 'liquid protein' diets.
Gelatin is claimed to generally promote joint health. A study at Ball State University, sponsored by Nabisco (the parent company of Knox gelatin), found that gelatin supplementation relieved knee joint pain and stiffness in athletes. The results remain to be reliably replicated by other researchers.
Due to the mad cow disease known as 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, demonstrated that the gelatin production process destroys most of the BSE prions that may have been present in the raw material (1).
(1) Grobben, A. H.; Steele, P. J.; Somerville, R. A.; Taylor, D. M. Inactivation of the bovine-spongiform-encephalopathy (BSE) agent by the acid and alkali processes used in the manufacture of bone gelatine. Biotechnology and Applied Biochemistry (2004), 39, 329-338.
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