SIMULTANEOUS DIFFUSION of CITRIC ACID and ASCORBIC ACID IN PREPEELED POTATOES

The study of the simultaneous diffusion of chemical preservatives in vegetable tissues permits the determination of the time required to complete this process and the concentration distributions of the preservatives.
The individual or simultaneous diffusion of citric and ascorbic acids in pre-peeled potatoes was analyzed; the effect of pH decrease on the diffusive flux of ascorbic acid and the interaction between both acids was considered as the multicomponent diffusion problem.
Potato spheres of different radii were immersed in individual solutions or mixtures of citric and ascorbic acids in concentration ranging from 0.5% to 2% W/V for different immersion times and agitation conditions. the residual concentration of citric acid was determined by titrable acidity (22058 AOAC method) and that of ascorbic acid by 2–6 dichlorophenol-indophenol method.
Experimental data were fitted to the mathematical models and the effective diffusion coefficients were determined for citric (D_e= 4.3 ± 0.2 × 10^?10 m²/s) and ascorbic acids (D_e= 5.45 ± 0.4 × 10^?10 m²/s) diffusing individually. When mixtures of two acids were used, multicomponent analysis was adopted and interaction coefficients were evaluated (D₁₂= 6.67 ± 0.8 × 10^?11 m²/s and D₂₁= 8.33 ± 0.8 × 10^?11 m²/s); they were an order of magnitude lower than binary diffusion values.
The pH effect on the diffusive flux of ascorbic acid was decoupled from the interaction of both acids during simultaneous diffusion by studying the diffusion of the first acid in potatoes preacidified with the second acid.