Gelatin is a kind of protein, which is boiled with animal skins or bones, and the price of gelatin is not expensive.

Gelatin is a water-soluble protein mixture. Collagen in skin, ligaments and tendons is partially hydrolyzed by acid or alkali or boiled in water. It is colorless or yellowish transparent fragments or coarse powder, which swells in water at 35 ~ 40℃ to form gel (water content is 5 ~ 10 times of its own weight). Protein is undernourished and lacks some essential amino acids, especially tryptophan, which is widely used in food and making adhesives, photographic negatives and filters.