Gelatin

Gelatin is a protein produced by the partial hydrolysis of collagen, the fibrous protein that lends strength to skin, tendon, bone, and other connective tissues in animals. In its dry state it is roughly ninety-eight to ninety-nine percent protein, and its amino-acid makeup is distinctive: glycine accounts for about a third of the residues, with proline and hydroxyproline also present in large amounts ^[1]. When gelatin is dissolved in warm water and then cooled, its chains partly reassemble into collagen-like triple helices held together by hydrogen bonds, forming a network that traps water as a gel; gentle warming melts the gel again, so the change is thermally reversible.

Commercial gelatin is made chiefly from the skins of pigs, the hides of cattle, and the bones of both, and it can also be prepared from fish and other marine sources. Manufacture begins with a pretreatment of the raw material, either with acid, which yields so-called type A gelatin, or with alkali such as lime, which yields type B; the conditioned collagen is then extracted with hot water, and the solution is filtered, concentrated, dried, and milled into granules or sheets ^[1]. The strength of the resulting gel is graded by a measure known as the Bloom value.

Gelatin has a broad range of applications ^[1][2]. In food it acts as a gelling, thickening, and stabilizing agent in products such as gummy candies, marshmallows, aspic, desserts, and some yogurts. In pharmacy it forms the hard and soft capsule shells that enclose many medicines and supplements, and it serves as a stabilizer in certain vaccines, as a component of hemostatic sponges, and, historically, as a plasma volume expander. Beyond medicine it holds the light-sensitive silver halide crystals in photographic film and appears in cosmetics and various industrial goods.

Gelatin is closely related to, but distinct from, the products marketed as hydrolyzed collagen or collagen peptides ^[2][3]. Those are made by breaking gelatin or collagen down further into much smaller peptides that dissolve readily and no longer form a gel, and they are sold as supplements aimed at skin and joint health. Research on such peptides has reported that specific fragments, including prolyl-hydroxyproline, can appear in the blood after ingestion and can influence connective-tissue cells in laboratory models, although the clinical significance is still being studied ^[3]. As a food protein, gelatin is considered incomplete, since it lacks the essential amino acid tryptophan and is low in several others.

Gelatin is regulated as a food ingredient and pharmaceutical excipient rather than as a drug, and it is generally recognized as safe for these uses. Because it is derived from animal tissue, it is unsuitable for vegetarians or for certain religious diets unless sourced accordingly, and plant or microbial gelling agents such as agar, pectin, and carrageenan, along with cellulose-based capsule materials, are used as alternatives. Concern about the possible transmission of animal diseases has prompted controls on source materials and processing.

Very safe as a food-grade protein, with only minor GI complaints like fullness or mild upset in some people. It is not a complete protein, being low in some essential amino acids, so it should not replace higher-quality protein sources. Source and quality matter for purity, and those with specific animal-product restrictions should check the source.