Mass transfer during osmotic dehydration of pineapple

The diffusion coefficients of water and solutes are important parameters in the analysis, design and opti-misation of an osmotic dehydration process. This work estimated by Fick’s Law the diffusion coefficients of water and sucrose during the osmotic dehydration of slices of pineapple fruit in sucrose solution at different temperatures. In addition, it analysed the effect of the change in thickness (shrinkage) during the process, and the use of higher order terms in the analytical solution. The model results were in good agreement with experimental data of water loss and solid gain. The best fit was found when the shrink-age was considered in a simple model based on the solution of Fick’s Law. The equilibrium water content ranged between 34 and 36 % for a 60 % w/w sucrose solution and was practically independent of temperature. Equilibrium sugar content increased from 45 to 54 % as the temperature rose from 30 to 50°C. Thickness variation was found to be independent of temperature and was only dependent on water content. Key Words: pineapple, osmotic dehydration, diffusion coefficient