The effects of the transformation processes of tomatoes especially using supercritical CO2 on bioavailability and extractability of lycopene is tried to be investigated. The experimental extraction curves measured on dried vegetable samples, obtained from different transformation processes of tomatoes, have been correlated with an equation of the type of a Langmuir gas adsorption isotherm and with a mathematical model based on differential mass balances written on a section of the extraction bed. In the second case it has been verified, both from literature and experimental data, that only the external mass transfer resistance controls the extraction process and under this hypothesis the model was developed by using a constant value for the mass transfer coefficient.

Lycopene is a carotenoid mainly contained in the fresh tomatoes as red pigment. The importance of this compound is due to its antioxidant activity, which is fundamental in the treatment of cardiovascular diseases, aging degenerations and some cancer forms. Lycopene is very stable inside the vegetable cells of the deep red tomatoes but unfortunately in this situation its bioavailability is very low. On the opposite the assimilation of the carotenoid is really easy from cooked foods especially in presence of oils and fats because of the high solubility of lycopene in non polar solvents. Processing and packaging the fresh tomatoes lead to the degradation of the pigment by oxidation and isomerization. Consequently it is important to define the relations between the concentration of lycopene and the variables (as air, light and heat) influencing the preservation of the active principle during the transformation processes of tomatoes. Thermal processing has been widely employed for concentrating and increasing the bioavailability of lycopene from ripe tomatoes: it has been demonstrated, by different authors,

that this kind of treatment doesn’t produce relevant losses of active principle. A recent process employs high hydrostatic pressures to preserve active principles contained in vegetables and fruits. In this case principle concentrations and antioxidant activity don’t change but the treatment induces structural modifications in the vegetable tissues, which are responsible for a different extractability of the compounds held inside the cells.

Figure 62: Experimental apparatus for extraction with SF-CO2.

Preliminary studies on the tomatoes matrices have been performed in order to determine the treatments that preserve and concentrate better lycopene. Fourteen different samples were treated with THF/MeOH (1:1 by weight) and the solutions were analysed with the UV spectrophotometer,after one day, in order to determine the active principle quantity after the complete release of lycopene from the vegetable matrix. Afterwards, the extraction with SF-CO2 has been carried out on the samples with higher concentrations of carotenoids, since the more concentrated samples can be effective in biological applications. Six samples have been selected to perform the extraction of lycopene.

Table 25: Lycopene concentrations in the tomato matrixes (by UV technique).

The study of the effects of the transformation processes of tomatoes on the extractability of lycopene has great importance. It has been demonstrated by spectrophotometric tests that the concentration of the vegetable matrices leads to higher percentages of recovered lycopene after the extraction with supercritical CO2. The discussion of the experimental data revealed that the concentrated samples treated at high hydrostatic pressures release high percentages of lycopene after the extraction with supercritical CO2 proving the good influence of this new technique on the recovering of the active principle.