[Degradation of the constituents in solubilization process of donkey skin]

Dry donkey skin, defatted in advance with hair scraped off, was separately solubilized by heating in sealed tubes at 130 degrees C for 2, 4, 6, 8h. The resultants were clarified and dried as Ejiao, whose yield appeared to reach maximum after 4h heating. Absorptivities of all four Ejiao preparations were in good approximation to standard gelatin. However, their intrinsic viscosity declined in order of prolonged solubilization process, indicating that depolymerization of donkey skin gelatin had taken place. In addition, significant degradation of dermatan sulfate, another constituent of Ejiao, was detected electrophoretically and photometrically.