## 5 Conclusions  
In this work, extraction tests on dried and ground tomato peels were performed by an innovative system using Norflurane as a solvent in subcritical conditions, with the purpose of extracting lycopene and \(\beta\)-carotene from tomato pomace. Low extraction yields of 0.005 \(\pm\) 0.001 mg/mg and 0.074 \(\pm\) 0.002 mg/mg for lycopene and \(\beta\)-carotene, respectively, were obtained after 2 h of process.  
To improve lycopene and \(\beta\)-carotene extraction yields, oleaginous co-matrices, ground tomato seeds, and wheat germ flour, were used. To exploit the presence of lipid fractions with a twofold function of co-solvents and preserving/stabilizing agents towards carotenoids, tomato seeds or wheat germ flour were mixed with tomato peels or layered in the upper part of the extraction bed.  
In general, the layered arrangement of the matrices provided a more significant enrichment of oils in both lycopene and \(\beta\)-carotene, in comparison with peels alone or peels mixed with the co-matrices inside the extraction chamber.  
When the layered configuration was used, a significant improvement of the extraction performances was observed, and lycopene yields of 0.132 \(\pm\) 0.010 mg/mg and 0.123 \(\pm\) 0.008 mg/mg were reached in 2 h of process, using tomato seeds and wheat germ flour, respectively, as co-matrices. In both cases, the improvement in \(\beta\)-carotene recovery resulted in being much higher than that observed for lycopene, and yields of 0.733 \(\pm\) 0.037 and 0.842 \(\pm\) 0.043 mg/mg were obtained in the presence of tomato seeds and wheat germ, respectively, after 2 h of process. Lycopene concentration in the oily extracts was approximately 0.3 mg/g\({}_{\rm oil}\) while the enrichment in \(\beta\)-carotene resulted to be more pronounced, with concentrations of 0.733 mg/g\({}_{\rm oil}\) and 0.952 mg/g\({}_{\rm oil}\) in wheat germ and tomato seed oils, respectively.  
The good affinity of the two carotenoids with the co-solvents, and their key role in the extraction improvement, were confirmed by a solubility study based on Hansen Theory. The relative solubilities estimated for the two carotenoids in Norflurane were quite similar to those evaluated with respect to CO\({}_{2}\): this attested the fundamental role of the strongeroperating conditions used in sc-CO\({}_{2}\) processes, which usually ensure better extraction performances than those obtained using Norflurane.  
Although the state of the art shows better results with supercritical CO\({}_{2}\) in terms of effective solubility of lycopene and extraction yields, the continuous solvent regeneration and recirculation, the milder operating conditions required by the Norflurane process investigated in this work, and the optimization of the process through the choice of suitable co-matrices and reactor configurations could compensate these low solubilities and ensure satisfactory performances by means of an economically more-convenient extraction system.  
Conceptualization, I.G. and R.N.; methodology, R.C.C., M.G., I.G. and R.N.; validation, R.C.C., M.G. and I.G.; investigation, R.C.C., L.V. and I.G.; formal analysis, R.C.C. and M.G.; visualization, R.C.C. and I.G.; data curation, R.C.C., M.G., L.V. and I.G.; writing--original draft, R.C.C.; writing--review and editing, R.C.C.; supervision, I.G. and R.N.; project administration, I.G. and R.N. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.