Gelatin or gelatine (from Latin: gelatus meaning "stiff", "frozen") is a translucent, colourless, brittle (when dry), flavourless foodstuff, derived from collagen obtained from various animal by-products.
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.
It is found in most gummy candy as well as other products such as marshmallows, gelatin dessert, and some ice cream, dip 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.
When added to boiling water and cooled, unflavored gelatin can make a home-made hair styling gel that is cheaper than many commercial hair styling products, but by comparison has a shorter shelf life (about a week) when stored in this form (usually in a refrigerator). After being applied to scalp hair, it can be removed with rinsing and some shampoo. It is commonly used as a biological substrate to culture adherent cells. It may be used by those who are sensitive to tannins (which can irritate the stomach) in teas, soups or brews. It may be used as a medium with which to consume LSD. LSD in gelatin form is known as "windowpane" or "geltabs." Gelatin is used to make the shells of paintballs, similar to the way pharmaceutical capsules are produced. Gelatin is used as an ingredient in implantable medical devices, such as in some bone void fillers. Gelatin is used in nail polish remover and makeup applications. The gelatin is often tinted in different colours to match a model's natural skin tone. Leaf or sheet gelatin is used directly in food-based model-making, for example to make translucent, edible, diamond-paned windows in gingerbread houses. Gelatin can be used as a binding agent in india ink.
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, 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 respects, closely similar to that of its parent collagen. Photographic and pharmaceutical grades of gelatin are generally sourced from beef bones.
Gelatin forms a viscous solution when dissolved in hot water, which sets to a gel on cooling. Gelatin added directly to cold water does not dissolve well. Gelatin is also soluble in most polar solvents. Gelatin solutions show viscoelastic flow and streaming birefringence. 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.
The mechanical properties of gelatin gels are very sensitive to temperature variations, the previous thermal history of the gel, and time. These 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 human body temperature, a factor which is important for mouthfeel of foods produced with gelatin. The viscosity of the gelatin/water mixture is greatest when the gelatin concentration is high and the mixture is kept cool (≈ 4 °C). The gel strength is quantified using the Bloom test.