Crosslinking of gelatin by aqueous peroxydisulfate

Abstract

Abstract Aqueous gelatin (5%) is crosslinked in the presence of 0.040–0.020 M peroxydisulfate at 70°C., but in 0.40 M peroxydisulfate, gelatin initially is crosslinked and then redissolves to give a solution of reduced viscosity. The rate of crosslinking depends on the concentration of peroxydisulfate, the nature of peroxydisulfate's cation, and the pH range of the solution during crosslinking. Addition of silver ion to gelatin–peroxydisulfate solutions increases the rate of crosslinking, whereas addition of hydroquinone inhibits crosslinking. Further, induced decomposition of peroxydisulfate is observed in the presence of gelatin. Acetylated and esterified gelatins are crosslinked by aqueous peroxydisulfate, but the ability of deaminated gelatin to crosslink is greatly reduced. Crosslinking is believed to proceed via sulfate and hydroxyl free‐radical attack of gelatin, with in situ generation of reactive intermediates that crosslink with other reactive sites in gelatin. Possible sites of crosslinking in gelatin have been suggested in light of viscosity data, chemical and amino acid analyses, and peroxydisulfate's known mode of decomposition.