A model food system for mass transfer in the acidification of cut root vegetables

The main objective of this work was to assess the adequacy of a 5% agarose gel to simulate the acetic acid acidification process in cut raw root vegetables. The process was well described by a Fickian model, and temperature dependence of diffusivity followed Arrhenius behaviour from 20 to 70°C with an activation energy of 16.8 kJ mol⁻¹. Equilibrium conditions were described with a constant partition coefficient of 0.94. External resistance to mass transfer was measurable under stagnant conditions and the mass transfer coefficients also changed with temperature as in an Arrhenius type equation with activation energy of 17.8 kJ mol⁻¹. Raw turnips and potatoes were acidified for comparison and the acid uptake followed a similar behaviour, although some differences in the parameters were observed. In general terms it was concluded that the 5% agarose gel is a suitable model food for studying acetic acid processing of raw root vegetables with exposed cut surfaces.