Valorisation of tomato peel waste for lycopene encapsulation: Optimization and comparison of two green techniques

Lycopene, a lipid-soluble carotenoid with potent antioxidant properties, is typically found in tomato peels, which are often discarded as by-products in the food industry. This study focused on extracting lycopene using solvent extraction and encapsulating it in polycaprolactone (PCL), a biodegradable polymer, using two different methods: solvent evaporation and supercritical emulsion extraction (SEE). Both methods were used to produce microparticles for nutraceutical applications. An optimization study based on Box-Behnken design and response surface modelling was conducted to assess the effects of emulsification stirring speed, emulsification time, and polymer amount on encapsulation efficiency and particle size. Particle sizes, measured by laser diffraction, ranged between 1.77 ± 0.10 and 2.82 ± 0.17 μm for solvent evaporation, and between 1.12 ± 0.03 and 2.72 ± 0.15 μm for SEE. Encapsulation efficiencies, measured by UV–vis spectroscopy, ranged between 28.45 ± 0.28 % and 89.94 ± 1.70 % for solvent evaporation, and between 66.52 ± 0.64 % and 89.45 ± 1.31 % for SEE. Results show that SEE yields more consistent encapsulation efficiencies compared to solvent evaporation. Additionally, the design of experiments (DoE) approach helped identify optimal conditions that minimize waste and maximize productivity. This work offers a sustainable method for converting agro-industrial waste into valuable nutraceutical products.