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download articleGelatin
Gelatin is a popular gelling agent. Gelatin is obtained from bones, skins and tissue of animals. Usually by-products from a slaughterhouse of cows, pigs and fish is used. Since 2001 the bones of cows may not be used anymore for feed and food in the EU. These bones may only be used for gelatin for technical applications.
Gelatin is
water soluble and digestible and is a gel that is strong, flexible and transparent.
Production process of gelatin
Reception, examination, sorting, cutting en purification
The bones, tissues and/or skins of cows and pigs are delivered from the slaughterhouse. The rotten and unusable parts are removed during the examination. Afterwards, the bone parts are sorted by size. After
sorting there are 3 fractions. The A and B fraction are stored to be further processed to gelatin. The C fraction consists of too small particles. This fraction cannot be used for the production of gelatin. In order to make skins and tissues more workable they are cut in pieces with a diameter of several centimeters. Afterwards, the undesired parts of bones, tissues and skins are hosed with a powerful jet of water.
Degreasing and roasting
The fat content is reduced to 2% by
soaking the parts in hot water. The fat melts and can be sucked from or skimmed off the water surface. Subsequently, the low fat pieces are dried and roasted by
heating them at a
temperature of 100°C for 30 minutes.
Purifying with acid and lye
Afterwards the minerals are removed from the bone pieces and bacteria are killed.
This is reached by
washing the pieces several times with acid (4% hydrochloric acid with a
PH below 1.5). In this process, the calcium carbonates are dissolved from the pieces. These calcium carbonates are further processed to dicalcium phosphate. After the acid purification the material is called oseine.
After the purification with acid the oseine is neutralized by washing it several times with water. Afterwards it is washed several times with a sodium hydroxide or a potassium hypochlorite solution to kill micro-organisms. It is washed a several times in order to neutralize it and to rinse it from remainders. The total purification process with acid and lye takes 12 to 20 hours.
Loosening protein compounds
Collagen, the protein of which gelatin is made, has strong compounds in the material. These compounds are to be loosened, which can be achieved by soaking it in lime milk. By soaking them for 20 to 40 days in this lime
milk the collagen can melt during the extraction. After the treatment with calcium carbonates it is crudely purified on a vibrating filter.
Extraction
In order to convert the loosened collagen into gelatin the oseine is heated, which is also called
extraction or
melting. The bones, tissues and skins are boiled in water. The water that is added has a starting temperature of 55°C. Later in the process water of 95°C is added. The higher the temperature is the lower the gelling capacity of the gelatin. Therefore, it is extracted three times at increasing temperatures. By lightly acidifying the solution the collagen more rapidly converts into gelatin, which increases the efficiency. Acidifying can happen by adding sulphuric acid. After all the collagen has been concerted into gelatin, after about 15 hours, it has a gelatin solution with 5% gelatin.
Filtering
After the extraction the solution is separated from bone pieces. This solution is very turbid. After filtration a clean and clear crystal gelatin is obtained.
Neutralizing
Because the gelatin solution is lightly acidified during the
boiling process it is now neutralized. It can be neutralized by adding sodium hydroxide. Sodium hydroxide splits in the water into sodium ions and hydroxide. The hydroxide together with the hydrogen forms water.
Demineralization
In demineralizing the liquid is tempered. Metals and residual salts are also removed. These elements could originally be part of the solution or added later during the process, like with extracting and neutralizing. These elements can be removed from the gelatin by means of an ion exchanger.
Concentrating and sterilizing
Afterwards the mass is concentrated by means of evaporation under
vacuum. The gelatin solution is concentrated from a concentration of 5% to 22%. Next it is sterilized in order to kill all micro-organisms and thus to guarantee the storage life. Sterilization at a temperature of 140°C for 4 seconds gives the desired result.
Additions
Sometimes additions are added to the gelatin. These additions can be coloring or flavoring agents or
sweeteners. During this phase of the process the additions can be mixed in the (still warm) gelatin. For the production of jelly sugar,
sugar is mixed with gelatin powder.
Cooling
The concentrated gelatin solution is then cooled in a scraped heat exchanger. In this heat exchanger the mass is cooled to 4°C. Gelation of the gelatin occurs when it is cooled. The gelatin is pressed through the heat exchanger through a template and leaves the heat exchanger as spaghetti.
Drying
The strings of gelatin are dried by blowing sterile and warm
air over it. The sterile air is necessary to prevent infection.
Grinding
In order to obtain gelatin powder the final production step is grinding. The size of the powder can be settled in the
grinding process.
Gelatin sheets
Gelatin is also available in thin sheets of gelatin. After the step with the additions the gelatin mass flows in a very thin layer on a plate. Afterwards it is cooled off by gelatin gelates. The plate can be cut into sheets with the desired sizes. These sheets are dried by means of sterile and hot air.
Packing
The sheets of gelatin and the gelatin powder are usually packed in plastic bags that are sealed. For the industry the gelatin is packed in large bags. Dry gelatin can be stored for several years.
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