Modeling oil migration in two-layer chocolate–almond confectionery products Original Research Article

Migration of oil from high oil content fillings into the surrounding chocolate coatings results in product quality changes of filled confections. The objective of this study was to evaluate the mass transfer of liquid oil in two-layer model confectionery samples prepared from four almond products and dark chocolate. Experimental data were acquired using magnetic resonance imaging (MRI). The spatial and temporal experimental data of the liquid oil signal of the almond product and chocolate were modeled using a Fickian diffusion model. Solutions to the diffusion model were derived using both Laplace transform analytical solution and a finite difference numerical solution. For both methods, the boundary condition between the two layers incorporated a partition coefficient. MatLab’s nlinfit routine coupled with the diffusion equation solution provided estimates of the diffusion coefficients, Da (almond products) and Dc (chocolate), and the partition coefficient. The diffusion coefficient values for the chocolate region ranged between 3 × 10−11 m2/s and 6 × 10−11 m2/s; the diffusion coefficient values for the almond products were an order of magnitude greater than that of chocolate.