This study focuses on the diffusion phenomena in ethanol-water systems. The diffusion coefficient of ethanol-water systems has a strong concentration dependency originating from intermolecular interactions and the association of molecules in solution. Recently, it has been suggested that flavor variation in whiskey is partly due to different storage conditions that can affect molecular structure variation. To evaluate the molecular structure variation, diffusion coefficient measurements are considered effective. To quantitatively evaluate the variations in the diffusion process and measure the mass diffusion coefficient, the analysis method was improved to measure the concentration field more precisely. Two ethanolic solutions were prepared in this study: one preserved under normal conditions and the other was stored under isothermal conditions for 496 days. By comparing diffusion processes occurring under different storage conditions, the different diffusion coefficients were determined and the effect of storage conditions was discussed. The diffusion coefficient of the ethanolic solution stored under an isothermal condition was smaller than that of the solution stored under normal conditions.
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