Gelatin is a macromolecular hydrocolloid, which is the product of partial hydrolysis of collagen. According to its properties and uses, it can be divided into photographic gelatin, edible gelatin and industrial gelatin. According to different uses, the quality requirements for gelatin are also different. When used as a binder, the main requirement is the bonding strength. When used in photography, food, medicine and other fields, the purity of the product is emphasized.
Collagen molecule is a helix formed by three polypeptide chains intertwined with each other. Through the process of processing, the collagen molecule helix is denatured and decomposed into an α-component of a single polypeptide chain (α-chain) and a β-group composed of two α chains. It can be divided into the γ-component composed of three α chains, and the molecular chain fragments between and smaller than the α-component or larger than the γ-component. It can be seen that gelatin is a polydisperse system with a certain molecular weight distribution, and its molecular weight distribution varies with different process conditions, which affects the physical and chemical properties of gelatin.