Sugar diffusivity in agar gel/milk bilayer systems

To study sucrose and lactose transfer between a dairy product and a fruit layer, this system was modelled with milk on the top of a gel containing 1.5% agar, 0.5% citric acid and different concentrations of sucrose (22.8, 43.3 and 61%). Average disaccharide concentrations at different locations were determined for the system after different diffusion times. Experimental data were fitted to a Fickian diffusion model with separate diffusivities in the milk and the agar gel phases, with correlation coefficient r(2) >0.98. The values of diffusivity estimated were close to those in aqueous solutions containing identical sucrose concentrations.