D-AMINO ACIDS IN NON-GELLING COMPONENTS OF GELATIN

As a possible cause of the non-gelling property of the sol fraction of gelatin, we considered that higher D-amino acid content should result in decreased formation of helices. The sol fractions were extracted f rom gelatin gels and hydrolyzed to amino acid mixtures. The rates of r eaction with D-amino acid oxidase (D-AOX) were recorded for the hydrol yzates. For a comparison, residual gels were also treated similarly. T he sol fractions always gave higher results than the residual gels for the three types of gelatin examined. The result also showed that the rates obtained from the sol fractions were in the order: limed ossein > limed hide > acid pigskin. To examine the reliability of this proced ure the D-form content for each amino acid in the sol from the limed h ide gelatin mas compared with that of the residual gel. The contents i n tile sol mere higher than those in the residue for most of the amino acids which racemized. The results indicate that the increased racemi zation of amino acids on the extraction of gelatin from raze materials is a cause of the non-gelling property.