[Moisture sorption of gelatin powder and collagen fibers]

Moisture sorption properties of gelatin powder and collagen fibers were investigated on the basis of the moisture sorption isotherm, the differential heat of moisture sorption, the decrease in entropy of moisture sorption and the parameter constants of the applicable isotherm equation. The amount of moisture sorbed on collagen fibers was larger than that on gelatin powder. The water molecules were absorbed on gelatin itself rather than on the active sites of gelatin. They were adsorbed on the polar groups of constitutive amino acids at amounts of moisture sorbed up to one or two monolayers and then were absorbed into collagen fibers at higher monolayers. They were kept loosely in gelatin and tightly in collagen. The structural stability of collagen to moisture was higher than that of gelatin.