Characterization of soft gelatin capsules by thermal analysis

Thermal analysis of soft gelatin capsule was used as a diagnostic tool to evaluate the effect of temperature and humidity stress conditions as well as formulation water, propylene glycol and ethanol on the softening of the gelatin shells. Results obtained using modulated and conventional DSC given as DeltaT(m) (change in gel-sol transition temperature) were compared with the results obtained using manual hardness tester given as % hardness loss. No difference between the two methods was observed in their ability to determine the extent of softening due to formulation water, propylene glycol and ethanol content. Thermal analysis and shifts in the reversible heat flow determined using MDSC provided additional insight into the structural changes and extent of deformation within the gelatin network upon exposure to formulation ingredients, temperature and humidity. Modulated thermal analysis is, therefore, a useful tool for screening the variables influencing the hardness of gelatin capsules.