MODIFIED GELATIN AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To obtain a modified gelatin low in reduction of an effective silver amount used in a physical aging and also low in physical suppressing property in a process for producing a halogenated silver particle emulsion for taking a photograph by blocking an imidazole group on the terminal of a histidine residue constituting a part of a gelatin. SOLUTION: This modified gelatin is obtained by blocking at least one group, preferably >=80% of terminal imidazole groups of histidine residues constituting a part of gelatin. Preferably, a method for adding a compound of the formula: O(COR)2 (R is an alkyl) (e.g. diethylpyrocarbonate) in an amount of about 100-500μmol/g based on the gelatin to an aqueous solution of the gelatin adjusted into pH at about 5-7 and subjecting the resultant aqueous solution to N-alkoxyformylation reaction at about the melting point of the gelatin is exemplified as the blocking method.