Exploring multicomponent equilibrium and cross-diffusion in osmotic dehydration: A new perspective on mass transfer

Abstract

Osmotic dehydration (OD) is often modeled using non-coupled (NC) mass transfer (MT) approaches, where equilibrium levels and diffusion coefficients of the involved species are determined independently and then related to the characteristics of the osmotic solution (OS). However, this approach fails to capture the real interactions between the substances being transferred. This study introduces a more comprehensive framework for analyzing multicomponent equilibrium and cross-diffusion during OD, offering new insights into the MT processes. The proposed theory was applied to the analysis of carrot OD in both binary and ternary systems at 40 °C, using NaCl (0–15 % w/w) and/or sucrose (0–55 % w/w) as solutes. The experimental design was carefully planned to facilitate the identification of interactions between components and included 11 treatments with a total of 28 triplicated kinetics. Water, NaCl, and sucrose kinetics were analyzed using both traditional NC and coupled (C) MT approaches to determine equilibrium levels and diffusion coefficients. The NCMT model required 28 separate diffusion coefficients, one for each solute and composition of the osmotic medium, to explain the MT rates, compared to only 6 in the cross-diffusion model. The cross-diffusion terms were able to explain artificial trends introduced by the NCMT approach, in which diffusion coefficients in the product appeared to vary with the composition of the OS. This allowed for a reinterpretation of MT phenomena during OD. The main diffusivities for water, NaCl and sucrose were found to be 3.73, 20.9 and 5.41 ( × 10⁻¹⁰) m²/s, respectively. The proposed approach could also be applied to other MT operations, such as bioactive impregnation, to deepen our understanding of these processes.