The critical temperature of gelatin from jelly to glue is usually 30-34℃. Above this temperature, gelatin will melt and become soft and sticky, that is, gelatin will melt at high temperature. Gelatin has no fixed structure and relative molecular weight, and will be partially degraded by collagen in connective tissues such as animal skin, bone, muscle membrane and muscle charm, and become white or yellowish, translucent and slightly shiny flakes or powder particles.
It is a colorless, odorless, nonvolatile, transparent and hard amorphous substance, which is soluble in hot water but insoluble in cold water, but it can slowly absorb water, swell and soften, and gelatin can absorb 5- 10 times the weight of water.