Aldehyde contents by MBTH method in gelatin have variation gelatin by gelatin. It has negative effect on photographic specificity, solubility in pharmaceutical capsule and browning by Maillard reaction in food. It was found that, aldehyde contents were changed by oxidation of gelatin in previous report. In case of strong oxidation, we find partially increased aldehyde as reducing sugars. Fatty acids were changed to aldehyde by oxidation, heat and light sources as well known in food science. Gelatin also contain many kind of fatty acid. We investigate morphological change of fatty acid to aldehyde by addition of fatty acid with oxidation.