In order to investigate the effect of phytic acid on the improvement of disintegration time (DT) of gelatin-based film sheets, gelatin film sheets and succinylated gelatin film sheets with various concentrations of phytic acid were dipped and stored in polyethylene glycol (PEG) 400 at 60 degrees C. The DT and near infrared (NIR) spectral changes were measured after storage. Gelatin showed a tendency to prolong DT caused by the formation of insoluble thin membranes due to the cross-linking of gelatin molecules, whereas succinylated gelatin did not show prolongation of DT. We also observed the preventive effect of phytic acid on the prolongation of DT of gelatin film sheets as the phytic acid concentration increased. From NIR measurements, it was considered that the -OH groups of phytic acid were coordinated with the hydrogen bonding position of gelatin molecules by replacing H2O or glycerin molecules. It was also thought that structural changes in the gelatin-water-glycerin complexes caused by phytic acid interfered with the access of peroxide or aldehyde generated from PEG 400 to the free epsilon-NH2 groups and prevented the cross-linking of gelatin molecules. On the other hand, because the free epsilon-NH2 groups of succinylated gelatin are protected by acid amidation, the cross-linking of succinylated gelatin was not observed.