Oil migration in confectionery products results in undesired quality changes of confections such as fat bloom. Oil migration and the resulting bloom formation in chocolate could be an important quality defect in a confectionery product. This study addressed to evaluate mass transfer of liquid oil on two-layer chocolate model systems prepared from hazelnut paste over different dark chocolate formulations by utilizing magnetic resonance imaging (MRI). Through the use of MRI, it becomes easier to predict the rate of migration and the effect of different ingredients on bloom formation. For five chocolate formulations stored at 30 A degrees C over a time frame of 22 days, experimental data acquired through MRI were modeled using a Fickian-based mathematical model to calculate diffusion coefficient (D). Using two different equations for boundary condition at upper chocolate surface, two models were evaluated and logistic type boundary model was shown to fit exhibit a better fit. In addition, associated constants (C-0, beta, t(0)) for time dependent upper boundary conditions were determined. Average diffusivities of all samples varied in the order of 10(-11) m(2)/s. This study addressed the potential use of MRI for visualization and quantification of migration for different chocolate formulations.