quickly in high voltage gradient operations as a consequence of
electrochemical reactions.
Assiry et al. (2003) compared the ascorbic acid degradation
kinetics in a buffer solution of pH 3.5 using conventional and ohmic
heating. The kinetics of degradation can be described adequately by
a first order model for both conventional and ohmic treatments, but
unlike conventional heating, the temperature dependence of
degradation for some ohmic treatments cannot be represented by
the Arrhenius relation. Electrode reactions, electrolysis of the solution,
as well as reactions between electrode materials and the
electrolysis products may all influence the reaction mechanism and
the kinetic parameters. These researchers observed a brown color to
the buffer solution, indicating the presence of ferric chloride. Insoluble
brown deposits were also observed on the electrode surfaces,
indicating the possible formation of iron(III) oxide or ferric chloride.
The results obtained in present study confirm the importance of
using either inert coatings on electrodes and sensors or high
frequency electric currents to control electrochemical reactions.
Further studies of the ohmic heating process should be conducted
to achieve a better understanding of the mechanisms involved in
the ascorbic acid degradation in the presence of oxygen and
metallic ions. In addition, other parameters should be evaluated to
compare both heating technologies. For example, studies of the
inhibition of enzymatic activity, the destruction of microorganisms
and the degradation of other important compounds (such as
anthocyanins and phenolic compounds) can be performed to
evaluate the potential of the ohmic heating process as an alternative
in the heat treatment of foods.