Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

摘要

Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmoti-cally dehydrated in sucrose solutions at 50,60, and 70 °Brix and at 35,45, and 55 ℃. Other experiments were done in a 70 °Brix sucrose solution at 35 ℃ with tomato slices of 4,6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20,40,80,160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh_s = 1.3 Re~(0.5) Sc_s~(0.15) and Sh_w = 0.11 Re~(0.5) Sc_w~(0.5), respectively. The effective diffusion coefficients of water (4.97 10~(-11) - 2.10 10~(-10) m~2/s) and sucrose (3.18 10~(-11) - 1.69 10~(10) m~2/s) depended only on temperature through an Arrhenius-type relationship.