Investigations on Oxidized Gelatins

Paper presented at a “Symposium on Photographic Gelatin” organized by the Scientific and Technical Group of the Royal Photographic- Society in Wadham College, Oxford. 2-6 September 1985.

Abstract

Starting from a native, inert bone gelatine three gelatins differing in the degree of oxidation were prepared. Photographic tests indicated an increase in fog and reduced grain growth restraining power with increasing degree of oxidation. Oxidation does not change the aldehyde concentration, but it reduces the gold-binding capacity and lowers the concentration of methionine and of tyrosine and causes hydroxylation of proline to hydroxyproline. Ornithine has been detected in all gelatins, while cysteine was found absent with the usual analytical methodes. The latter, however, has been found in a hydrolyzate prepared from bones. Addition small amounts of cysteine to an oxidized gelatin restores the properties to values similar to those of the initial native gelatin. Therefore, it is assumed that the native gelatin could contain small, not-detectable traces of cysteine which have been oxidized by the hydrogen peroxide treatment.

Notes

Paper presented at a “Symposium on Photographic Gelatin” organized by the Scientific and Technical Group of the Royal Photographic- Society in Wadham College, Oxford. 2-6 September 1985.