## 4 Discussion  
Extraction efficiencies, for both lycopene and \(\beta\)-carotene, in the presence of lipid co-solvents were significantly higher, of two orders of magnitude, than those obtained with peels alone. When the selected co-matrices were mixed with peels inside the extraction chamber, a simultaneous extraction of oil and carotenoids was observed, and the presence of solubilized oil in Noroflurane enhanced the release of carotenoids in the total extract. Furthermore, the layered arrangement of the matrices in the extraction bed showed to have a large effect on the extraction performances, which was more marked for \(\beta\)-carotene. By this configuration, solvent percolation occurred first through the co-matrix, during which Noroflurane enriched with oil, and then through the peel layer. In this way, all the available co-solvent that dissolves in Noroflurane came into contact with skins, enhancing the recovery of carotenoids, and functional extracts, rich in lycopene and \(\beta\)-carotene, were obtained. [PERSON] et al. [41] studied the lycopene solubilization in Jojoba oil, using 10% lycopene oleoresin, and found a lycopene concentration equal to 0.7 mg/100 g\({}_{\rm oil}\). [PERSON] et al. [42] measured a lycopene concentration value of 0.75 mg/100 g\({}_{\rm oil}\) using fresh peels or 10% lycopene oleoresin after a continuous 7 h stirring at 20 \({}^{\circ}\)C with a (1:1) mass ratio. In literature, the solubility in edible oils of \(\beta\)-carotene was reported equal to 0.08% at room temperature, 0.2% at 60 \({}^{\circ}\)C, and 0.8% at 100 \({}^{\circ}\)C [43]. As shown in Table 4, the quantity of lycopene extracted by Noroflurane with co-solvents is of the same order of magnitude as that obtained by running extractions with several combinations of common organic solvents at 35 \({}^{\circ}\)C for 1 h, using an excess of solvent (solid mass-to-solvent volume ratio of 1:30) to compensate the low solubility of carotenoids [40]. Extraction kinetics of lycopene and \(\beta\)-carotene were studied (trials #6 and #7), and the lycopene yield (approximately 10%) obtained in 2 h of process was quite similar to that reported by [PERSON] et al. [27], when the extraction was carried out using sc-CO\({}_{2}\) (at 90 \({}^{\circ}\)C, 20 MPa, with a solvent flow rate of 3 mL/min and 3 h of process time) and tomato peels and tomato seeds were mixed in the same mass ratio used in this work (37:63 \(w\)/w). The final yields obtained during trials #6 and #7 were slightly higher than those measured after 2 h continuous runs (trials #4/LSP and #5/LWGFP). It could be due to the intermittent conduction of the process, necessary for the sampling operations, that tended to improve the contact between Noroflurane and the matrix after each restart. The lycopene concentration measured in both TS and WGF oils was approximately constant (0.3 mg/g) during the process time and higher than the lycopene solubility value of 0.75 mg/100 g found in rapeseed oil by [PERSON] et al. [42]. Moreover, the concentration values of \(\beta\)-carotene in both oils were quite close to the theoretical values (0.95 mg/g and 1.21 mg/g in TS and WGF oils, respectively), defined as ideal concentrations obtainable if all the oil and carotenoids were completely extracted during the process. Furthermore, a decreasing trend during the last phases of the process was observed, owing to a lowering of the \(\beta\)-carotene extraction rate compared with that of oil. Data obtained with the extraction process investigated in this work allowed calculating the average effective solubilities of lycopene and \(\beta\)-carotene in Noroflurane. In the following Table 6, the calculated solubilities were compared to the values reported by various authors in literature, who investigated sc-CO\({}_{2}\) as an extracting solvent, without and with the presence of co-solvents. These data are not easily comparable due to the widely diversified process conditions, such as different feedstocks and various solvent flow rates fed to the extraction bed.