<P> Gelatin or gelatine (from Latin: gelatus meaning "stiff", "frozen") is a translucent, colorless, brittle (when dry), flavorless food ingredient that is derived from collagen obtained from various animal body parts . It is commonly used as a gelling agent in food, medications, drug and vitamin capsules, photographic films and papers, and cosmetics . </P> <P> Substances containing gelatin or functioning in a similar way are called "gelatinous". Gelatin is an irreversibly hydrolyzed form of collagen, wherein the hydrolysis results in the reduction of protein fibrils into smaller peptides, which will have broad molecular weight ranges associated with physical and chemical methods of denaturation, based on the process of hydrolysis . It is found in most gummy candy, as well as other products such as marshmallows, gelatin desserts, and some ice creams, dips, and yogurts . Gelatin for recipe use comes in the form of powder, granules, or sheets . Instant types can be added to the food as they are; others need to be soaked in water beforehand . </P> <P> Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs, and fish . During hydrolysis, the natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily . Its chemical composition is, in many aspects, closely similar to that of its parent collagen . Photographic and pharmaceutical grades of gelatin generally are sourced from cattle bones and pig skin . Gelatin has proline, hydroxyproline and glycine in its polypeptide chain . Glycine is responsible for close packing of the chains . Presence of proline restricts the conformation . This is important for gelation properties of gelatin . </P> <P> Gelatin readily dissolves in hot water and sets to a gel on cooling . When added directly to cold water, it does not dissolve well, however . Gelatin also is soluble in most polar solvents . Gelatin solutions show viscoelastic flow and streaming birefringence . Solubility 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 . </P>

What part of the pig is used to make gelatin