Preparation of Amidated Gelatins and Their Physicochemical Properties

Abstract

To learn of possible contributions of amide side-groups of asparagine and glutamine residues to viscoelastic properties of food proteins, lime-processed gelatin, which has lost these amide side-groups, was amidated by reaction with ammonia and the water soluble carbodiimide, 1-ethyl-3-dimethylaminopropyl carbodiimide (EDC). Depending on the quantity of EDC used, 13 to 40.3% of carboxyl side-groups of gelatin was amidated without intra- and inter-molecular cross-linkages, as judged from analyses of free-amino groups, gel-filtration chromatography, and sodium dodecyl sulfate-polyacrylamide gel-electrophoresis. The amidated gelatins had higher isoionic points as expected, but their regeneration of the triple helical structure of collagen was prevented as judged from analyses of circular dichroism. Gels made from amidated gelatins showed fairly high viscosity but low gel strength.