Gelatin (also gelatine) is a translucent brittle solid substance, colorless or slightly yellow, nearly tasteless and odorless, which is created by prolonged boiling of animal skin and connective tissue. It has many uses in food, medicine, and manufacturing.
Physical properties Edit
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 which are employed to extract the dried collagen hydrolysate and which may take several weeks. The worldwide production amounts to 250,000 tons per year.
As for home cooking, boiling certain cartilagenous cuts of meat, or bones, will result in gelatin being dissolved into the water. Depending on the concentration, the resulting broth, when cooled, will naturally form a jelly. This process may for instance be used for the pot-au-feu dish.
Edible gelatins Edit
Household gelatin comes in the form of sheets, granules or as a 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 in order to comply with Jewish kashrut or Muslim halal laws. Vegetarians and vegans may substitute similar gelling agents such as agar, pectin, or konnyaku sometimes incorrectly referred to as "vegetable gelatins." There is no chemical relationship; they are carbohydrates, not proteins. The name "gelatin" is colloquially applied to all types of gels and jellies, but properly used, it should refer solely to the animal protein product. There is no vegetable source for gelatin.
Probably best known as a gelling agent in cooking, different types and grades of gelatin are used in a wide range of food and non-food products:
Food uses Edit
Common examples of foods that contain gelatin are gelatin desserts or jelly, trifles, aspic, marshmallows and confectioneries such as Peeps and gummy bears. Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as ice cream, jams, yogurt, cream cheese, margarine; it is used, as well, in fat-reduced foods to simulate the mouth feel of fat and to create volume without adding calories.
Gelatin is used for the clarification of juices, such as apple juice, and of 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, isinglass was one of the oldest sources of gelatin.
Technical uses Edit
- Gelatin typically constitutes the shells of pharmaceutical capsules in order to make their contents easier to swallow.
- Animal glues such as hide glue are essentially unrefined gelatin.
- 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.
- Used as a carrier, coating or separating agent for other substances, it, for example, makes beta-carotene water-soluble, thus imparting a yellow color to any soft drinks containing beta-carotene.
- 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 "hydrolyzed collagen".
- As a surface sizing it smoothes glossy printing papers or playing cards and maintains 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 commonly used, the owners of the trademark object to the genericized use of the term.
- When added to boiling water and cooled, unflavored gelatin can make an effective home-made hair styling gel that is cheaper than many commercial hair styling products, but by comparison has a shorter shelf life (about a week) when stored in this form (usually in a refrigerator). Some people claim that gelatin/water-based hair gel does not cause hair to thin with constant long-term use, compared to commercial products because it does not contain certain chemicals. After being applied to scalp hair, it can be removed with rinsing and some shampoo. Striking results can be achieved when hair is held in place and a hair dryer is used, to create spikes, the Mohawk hairstyle, etc.
Medicinal properties Edit
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 to support such an assertion, one which may be traced back to Knox's revolutionary marketing techniques of the 1890s, when it was advertised that gelatin contains protein and that lack of protein causes dry, deformed nails. Actually, the human body itself produces abundant amounts of the proteins found in gelatin. Furthermore, 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 notable for its exceptionally low nutritional value. The approximate amino acid composition of gelatin is: glycine 21 %, proline 12 %, hydroxyproline 12 %, glutamic acid 10 %, alanine 9 %, arginine 8%, aspartic acid 6 %, lysine 4 %, serine 4 %, leucine 3 %, valine 2 %, phenylalanine 2 %, threonine 2 %, isoleucine 1 %,hydroxylysine 1 %, methionine and histidine <1% and tyrosine < 0.5 %. These values vary, especially the minor constituents, depending on the source of the raw material and processing technique(3).
Gelatin is unusually high in the non-essential amino acids glycine and proline, (i.e., those produced by the human body), while lacking certain essential amino acids (i.e., those not produced by the human body). Gelatin 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 promote general joint health. A study at Ball State University, sponsored by Nabisco (the former parent company of Knox gelatin), found that gelatin supplementation relieved knee joint pain and stiffness in athletes. These results remain yet to be replicated by other researchers.
It has been claimed that an early procedure for creating gelatin was discovered by a 17th-century Franciscan Abbot who was seeking a way to purify human blood. Having failed in this endeavor, he noted that his method of solidifying fluid might be more useful with water, although the supposed records of this were allegedly lost during the Nazi invasion of France. NNOO!!O!!!!
Safety concerns Edit
Due to Bovine spongiform encephalopathy (BSE), also known as "mad cow disease", and its link to the Creutzfeldt-Jakob disease, there has been much concern about using gelatin derived from possibly infected animal parts. One study released in 2004, however, demonstrated that the gelatin production process destroys most of the BSE prions that may be present in the raw material (1). However, more detailed recent studies regarding the safety of gelatin in respect to mad cow disease have prompted the U.S. Food and Drug Administration to re-issue a warning and stricter guidelines for The Sourcing and Processing of Gelatin to Reduce the Potential Risk Posed by Bovine Spongiform Encephalopathy from 1997.
(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.
(2) Dr. Roland Heynke Gelatin Production and Prion Theory General Information about Gelatin and Mad Cow Disease including references to various studies.
(3) P.V. Stevens. Food Australia. 44(7): 320-324, 1992. Described on Dr Bernard Cole's website 2005-08-11.