Gelatin
For the art collective, see Gelitin.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,
connective tissue or
bones. It has many uses in food, medicine, and manufacturing. Substances that contain or resemble gelatin are called
gelatinous. Gelatin is also known as
E number E441.
Gelatin is a
protein product produced by partial
hydrolysis of
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 (roughly 500 million lbs).
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.
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,
nature gum,
carrageenan,
pectin, or
konnyaku sometimes referred to as "vegetable gelatins" although 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 currently refers 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
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
* Gelatin typically constitutes the shells of pharmaceutical
capsules in order to make their contents easier to swallow.
Hypromellose is the vegetarian counterpart to gelatin, but is more expensive to produce.
*
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.
Other uses
* 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 a 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). After being applied to scalp hair, it can be removed with rinsing and some shampoo.
* It is commonly used as a biological substrate to culture adherent cells
Although gelatin is 98–99% protein by dry weight, it has less nutritional value than many other protein sources. 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). It contains no
tryptophan and is deficient in
isoleucine,
threonine, and
methionine. 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 one of the few foods that cause a net loss of protein if eaten exclusively. Several people died of malnutrition in the 1970s while on popular 'liquid protein' diets.
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. In fact, 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.
Gelatin has also been claimed to promote general joint health. A study at
Ball State University, sponsored by
Nabisco (the former parent company of Knox gelatin[
1]), found that gelatin supplementation relieved knee joint pain and stiffness in athletes. These results remain yet to be replicated by other researchers.
Due to
Bovine spongiform encephalopathy (BSE), also known as "mad cow disease", and its link to the
Creutzfeldt-Jakob disease (CJD), 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.
