The annual global market for gelatin is approximately 325 thousand metric tons. Europe is the largest user of gelatin at 133 thousand metric tons. 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. Gelatin is derived mainly from pork skins, pork and cattle bones, or split cattle hides; contrary to popular belief, horns and hooves are not used. The raw materials are prepared by different curing, acid, and alkali processes which are employed to extract the dried collagen hydrolysate. These processes may take up to several weeks, and differences in such processes have great effects on the properties of the final gelatin products.
How Gelatin is Manufactured?
An explanation of the production of gelatins will help in understanding the properties and the characteristics which exist among the several types and grades.
Gelatin is derived from collagen, an insoluble fibrous protein which is the principal constituent of connective tissues and bones. Collagen is distinctive in that it contains an unusually high level of the cyclic amino acids proline and hydroxyproline. Collagen consists of three helical polypeptide chains wound around each other and connected by intermolecular cross-links.
Gelatin is recovered from collagen by hydrolysis. There are several varieties of gelatin, the composition of which depends on the source of collagen and the hydrolytic treatment used.
The principal raw materials used in gelatin production today are cattle bones, cattle hides, and porkskins. Extraneous substances, such as minerals (in the case of bone), fats and albuminoids (found in skin), are removed by proper pretreatment to give purified collagen. These pre-treated materials are then hydrolyzed to gelatin which is soluble in hot water.
Gelatin recovered from bone is used primarily in pharmaceutical applications: some is used for photographic purposes. The so-called green bone from the slaughter of cattle is cleaned, degreased, dried, sorted, and crushed to a particle size of about 1-2 cm. The pieces of bone are then treated with dilute hydrochloric acid to remove mineral salts. The resulting sponge-like material is called ossein. From this point on in the manufacture of Type B gelatin, both cattle hides and ossein receive similar treatment.
Cattle hides are available from trimming operations in leather production. Cattle hides are usually dehaired chemically with a lime/sulfide solution followed by mechanical loosening.
For the production of Type B gelatin, both ossein and cattle hide pieces are subjected to lengthy treatment with an alkali (usually lime) and water at ambient temperature. Depending on previous treatment, the nature of the material, the size of the pieces, and the exact temperature, liming takes 5-20 weeks, usually 8-12. The process is controlled by the degree of alkalinity of the lime liquor as determined by titration with acid, or by making test extractions.
Ossein usually requires more liming than cattle hides. Additional lime is added to maintain an excess, thereby compensating for any consumed. After conditioning, the raw material is thoroughly washed with cold water to remove excess lime; the pH adjusted with acid; and the product extracted with hot water to recover the soluble gelatin.
When porkskins are utilized for production of Type A gelatin they are washed with cold water and then soaked in cold dilute mineral acid for several hours until maximum swelling has occurred. Hydrochloric acid and sulfuric acid are most commonly employed. The remaining acid is then drained off and the material is again washed several times with cold water. The porkskins are then ready for extraction with hot water.
The pH, time, temperature, and number of extractions varies from processor to processor depending on product needs, type of equipment employed, time of operations, and economics. Extraction procedures are closely controlled in the manufacture of both type A and type B gelatin since they influence both quality and quantity. Although continuous extraction is used by some processors, most methods still employ discrete batch fractions. Extraction is normally carried out in stainless steel vessels equipped with provisions for heating and temperature control.
The number of extractions varies, 3-6 is typical. The first extraction generally takes place at 50-60-degrees C. The final extraction is carried out close to the boiling point. Extracts are kept separate, analyzed, and subsequently blended to meet various customer specifications.
Earlier extractions have higher molecular weights, higher viscosity, higher gel strength, and the least color. The later extractions are made at increasingly higher temperatures; the resulting product has lower molecular weight, lower gel strength, and greater color.
The dilute gelatin solutions from the various hot water extractions are filtered, deionized, and concentrated by cross-flow membrane filtration and/or vacuum evaporation. The gelatin solution is then chilled and either cut into ribbons or extruded as noodles, and the gelled material is deposited as a bed onto an endless, open weave, stainless steel belt. The belt is passed through a drying chamber, which is divided into zones in each of which the temperature and humidity of the drying air is accurately controlled. Typical temperatures range from about 30-degrees C in the initial zone up to about 70-degrees C in the final zone. The air is usually conditioned by filtration, dehumidification and tempering.
Drying involves progressive increases in air temperature, often with exhaustion of moist air and replenishment with conditioned air. Drying time is 1-5 hours, depending on the quality and concentration of the material and the exact conditions employed. The rate of drying is carefully controlled to avoid melting and case hardening. The gelatin leaves the dryer with a moisture content of about 10%. The dried bed is then broken into pieces that are ground to the required particle size.
Dried gelatin is tested for quality and gel strength according to standard methods developed by the Gelatin Manufacturers Institute of America.
Throughout the entire process, strict attention is paid to Good Manufacturing Practices to ensure the purity of the gelatin.
Although gelatins are sometimes referred to as edible, pharmaceutical, photographic or technical, these terms refer only to their uses, and not to the methods of manufacture. Same manufacturing process is generally followed for all these types of Gelatin.
(The above information and data are derived from the web sites of various Gelatin manufactures associations like http://www.gelatine.org/, http://www.gelatin-gmia.com/, http://www.sagma-gelatina.com, http://www.gmap-gelatin.com/ )