During the cherry tomato processing with combined methods,
the mechanisms of lycopene oxidization and trans–cis isomerization were favored, principally into the 13-cis form. When the osmotic pre-treatment was applied, a 10% rate of isomerization
was registered, although it was the non-osmotically dehydrated
samples that underwent the greatest degree of isomerization in
the subsequent drying stage. Regarding to the microwave energy
level, this turned out to be the most relevant parameter for the
changes experienced by the lycopene. In fact, the samples dehydrated at 3 W/g, and especially at 80 C, showed a greater level
of isomerization but a lower percentage of residual total lycopene.
The cherry tomato products showed different optical characteristics depending on the processing conditions applied. When convective drying was carried out at 40 C exclusively with hot air,
the samples showed more reddish tones and less luminosity in
comparison with fresh tomato. On the other hand, when microwave energy was applied there was an increase in luminosity,
and the colour of the samples changed towards more orange tones,
which is related to a greater presence of lycopene cis isomers in
these samples.