(492b) Determination of Effective Diffusion Coefficient of Water in Marshmallow

Dried marshmallows are a common component in breakfast cereals. Control of the drying process is important since a difference in the water activities of the various components decreases overall product quality; a relatively high water activity in the marshmallows results in wet cereal flakes at equilibrium, and relatively low activity results in dry flakes. Quantifying the effective diffusion coefficient allows for better understanding of the drying process and can lead to improvements in product quality. The effective diffusion coefficient of water in marshmallow (Dwm) was determined by using a combined experimental-computational approach. Marshmallow samples were placed in a desiccator using calcium sulfate, and sample weights were recorded until there was minimal change (<0.2%, dry basis) over a period of twelve hours. An axisymmetric finite-difference model was developed to simulate the experiment by accounting for internal mass transfer by diffusion and external mass transfer by natural convection. By minimizing the root-mean-square error between the experimental and simulation data, Dwm was determined to be 9.49 x 10^-11 ± 0.56 x 10^-11 m^2/s. Results also indicated that the experimental drying process is limited by internal diffusion (Bi > 1).