出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/07/12 15:02:15」(JST)
Gelatin (or gelatine) is a translucent, colorless, brittle (when dry), flavorless solid substance, derived from the collagen mainly inside pig skin (hide) and cattle bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar way are called gelatinous. Gelatin is an irreversibly hydrolysed form of collagen, and is classified as a foodstuff. It is found in some gummy candies as well as other products such as marshmallows, gelatin dessert, and some ice cream and yogurt. Household gelatin comes in the form of sheets, granules, or powder. Instant types can be added to the food as they are; others need to be soaked in water beforehand.
Gelatine is classed as a food in its own right and not subject to the food additives legislation in Europe. Gelatin has its own E number: 441.[1]
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Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, boiled crushed bones, connective tissues, organs and some intestines of animals such as domesticated cattle, chicken, and pigs. The natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily. Gelatin melts to a liquid when heated and solidifies when cooled again. Together with water, it forms a semi-solid colloid gel. Gelatin forms a solution of high viscosity in water, which sets to a gel on cooling, and its chemical composition is, in many respects, closely similar to that of its parent collagen.[2] Gelatin is also soluble in most polar solvents.
Gelatin solutions show viscoelastic flow and streaming birefringence. If gelatin is put into contact with cold water, some of the material dissolves, but not all. The solubility of the gelatin is determined by the method of manufacture. Typically, gelatin can be dispersed in a relatively concentrated acid. Such dispersions are stable for 10–15 days with little or no chemical changes and are suitable for coating purposes or for extrusion into a precipitating bath.
Gelatin gels exist over only a small temperature range, the upper limit being the melting point of the gel, which depends on gelatin grade and concentration (but is typically less than 35°C) and the lower limit the freezing point at which ice crystallizes. The upper melting point is below body temperature, a factor which is important for mouthfeel of foods produced with gelatin.[3]
Mechanical properties of gelatin gels (for example the gel strength, which is quantified using the Bloom test) are very sensitive to temperature variations, previous thermal history of the gel, and time. The viscosity of the gelatin/water mixture increases with concentration and when kept cool (≈ 4 °C).
The worldwide production amount of gelatin is about 300,000 tons per year (roughly 600 million lb).[citation needed] On a commercial scale, gelatin is made from by-products of the meat and leather industry. Recently, fish by-products have also been considered because they eliminate some of the religious obstacles surrounding gelatin consumption.[3] Gelatin is derived mainly from pork skins, pork, horse, and cattle bones, or split cattle hides; contrary to popular belief, horns and hooves are not used.[4] The raw materials are prepared by different curing, acid, and alkali processes which are employed to extract the dried collagen hydrolysate. These processes[5] may take up to several weeks, and differences in such processes have great effects on the properties of the final gelatin products.[6]
Gelatin can also be prepared in the home. Boiling certain cartilaginous 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 or gel. This process is used for aspic.
While there are many processes whereby collagen can be converted to gelatin, they all have several factors in common. The intermolecular and intramolecular bonds which stabilize insoluble collagen rendering it insoluble must be broken, and the hydrogen bonds which stabilize the collagen helix must also be broken.[2] The manufacturing processes of gelatin consists of three main stages:
If the physical material that will be used in production is derived from bones, dilute acid solutions are used to remove calcium and similar salts. Hot water or several solvents may be used for de-greasing. Maximum fat content of the material should not exceed 1% before the main extraction step. If the raw material is hides and skin, size reduction, washing, removing hair from the hides, and de-greasing are the most important pretreatments used to make the hides and skins ready for the main extraction step. Raw material preparation for extraction is done by three different methods: acid, alkali, and enzymatic treatments. Acid treatment is especially suitable for less fully crosslinked materials such as pig skin collagen. Pig skin collagen is less complex than the collagen found in bovine hides. Acid treatment is faster than alkali treatment and normally requires 10 to 48 hours. Alkali treatment is suitable for more complex collagen, e.g., the collagen found in bovine hides. This process requires longer time, normally several weeks. The purpose of the alkali treatment is to destroy certain chemical crosslinkages still present in collagen. The gelatin obtained from acid treated raw material has been called type-A gelatin, and the gelatin obtained from alkali treated raw material is referred to as type-B gelatin. Enzymatic treatments used for preparing raw material for the main extraction step are relatively new. Enzymatic treatments have some advantages in contrast to alkali treatment. Time required for enzymatic treatment is short, the yield is almost 100% in enzymatic treatment, the purity is also higher, and the physical properties of the final gelatin product are better.
After preparation of the raw material, i.e., reducing crosslinkages between collagen components and removing some of the impurities such as fat and salts, partially purified collagen is converted into gelatin by extraction with either water or acid solutions at appropriate temperatures. All industrial processes are based on neutral or acid pH values because though alkali treatments speed up conversion, they also promote degradation processes. Acid extract conditions are extensively used in the industry but the degree of acid varies with different processes. This extraction step is a multi stage process, and the extraction temperature is usually increased in later extraction steps. This procedure ensures the minimum thermal degradation of the extracted gelatin.
This process includes several steps such as filtration, evaporation, drying, grinding, and sifting. These operations are concentration-dependent and also dependent on the particular gelatin used. Gelatin degradation should be avoided and minimized, therefore the lowest temperature possible is used for the recovery process. Most recoveries are rapid, with all of the processes being done in several stages to avoid extensive deterioration of the peptide structure. A deteriorated peptide structure would result in a low gelling strength, which is not generally desired.
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: Common examples of foods that contain gelatin are gelatin desserts, trifles, aspic, marshmallows, candy corn, and confections such as Peeps, gummy bears and jelly babies. Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as jams, yogurt, cream cheese, and margarine; it is used, as well, in fat-reduced foods to simulate the mouthfeel 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 used as a fining agent for wine and beer.[7] Beside hartshorn jelly, from deer antlers (hence the name "hartshorn"), isinglass was one of the oldest sources of gelatin.
Special kinds of gelatin indicate the specific animal that was used for its production. For example, Muslim halal or Jewish kosher customs may require gelatin from sources other than pigs, like cows and/or fish and from animals slaughtered ritually. Muslims do not eat foods or use products that contains pork gelatin. There are many companies that specify the source of the gelatin used, and advise consumers via the nutrition information and/or their hotline.[citation needed] Likewise, Hindu customs may require gelatin-alternatives from sources other than animals. Many Hindus are vegetarian. The few Hindus who are not vegetarians don't mind gelatin from all the sources but cow, which is considered sacred. Vegans and strict vegetarians choose not to eat foods containing gelatin made from animals.Romani people are cautious of gelatin products that may have been made from horses, as their culture forbids consuming horses.
Some dietary or religious customs forbid the use of gelatin from certain animal sources, and medical issues may limit or prevent its consumption by certain people.
Alternatives to gelatin include non-animal gel sources such as agar-agar (a seaweed), carrageenan, pectin, konjak, and guar gum.
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.[11]
Several Russian researchers offer the following opinion regarding certain peptides found in gelatin: "gelatin peptides reinforce resistance of the stomach mucous tunic to ethanol and stress action, decreasing the ulcer area by twice."[12]
Gelatin is also a topical haemostatic. A piece of gelatin sponge of appropriate size is applied on bleeding wound, pressed for some time and tied in bandage. Haemostatic action is based on platelets damage at the contact of blood with gelatin, which activates the coagulation cascade. Gelatin also causes a tamponading effect - blood flow stoppage into a blood vessel by a constriction of the vessel by an outside force.[13]
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,[14] found that gelatin supplementation relieved knee joint pain and stiffness in athletes.[15]
Oral gelatin consumption have been claimed to have beneficial therapeutic effect on hair loss in both men and women.[16][17][18][19][20][21][22][23]. In addition there are scientific publications that present evidences that consumption of oral gelatin has beneficial effect for some fingernail changes and diseases.[24][25][26][27][28]
Strict regulations apply for all steps in the gelatin manufacturing process. Gelatin is produced from natural raw materials which originate from animals that have been examined and accepted for human consumption by veterinary authorities. Hygienic regulations with respect to fresh raw materials are ensured and each batch of raw material delivered to the manufacturing plant is immediately checked and documented. (Citation Needed)
In addition to the raw material quality, also the production process itself is an effective quality assurance measure. In the production process a comprehensive monitoring system ensures that potential risks are minimized. (Citation Needed)
The U.S. Food and Drug Administration (FDA), with support from the TSE (Transmissible spongiform encephalopathy) Advisory Committee, has since 1997 been monitoring the potential risk of transmitting animal diseases, especially bovine spongiform encephalopathy (BSE), commonly known as Mad Cow disease. The FDA study concluded: "...steps such as heat, alkaline treatment, and filtration could be effective in reducing the level of contaminating TSE agents; however, scientific evidence is insufficient at this time to demonstrate that these treatments would effectively remove the BSE infectious agent if present in the source material."[29]
The Scientific Steering Committee (SSC) of the European Union (EU) in 2003 stated that the risk associated with bovine bone gelatin is very low or zero.[30][31] In 2006 the European Food Safety Authority (EFSA) stated that the SSC opinion was confirmed, that the BSE risk of bone-derived gelatin was very small, and removed support for the 2003 request of excluding the skull and vertebrae of bovine origin older than 12 months from the material used in gelatin manufacturing.[32]
All reputable gelatin manufacturers today follow the Quality Management System according to ISO 9001 to comply with all required physical, chemical, microbiological and technical production and quality standards. In this way all process steps follow international laws and customer-specific quality parameters and are guaranteed and documented. For pharmaceutical grade gelatins strict regulations from the Food and Drug Administration (FDA), the European CPMP's regulation and European Pharmacopoeia must be met. A detailed overview of the regulatory requirements for gelatin production can be found in the Gelatine Handbook, page 99-101.[33]
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| リンク元 | 「chunky」「gelatine」「ゼラチン質」「ゼラチン状」 |
| 拡張検索 | 「gelatinous ascites」「gelatinous drop-like corneal dystrophy」 |