Extraction of Lycopene from Tomato Peels Using Supercritical Carbon Dioxide and Conjugation of the Extracted Lycopene with TiO2Nanoparticles

Imagine turning tomato peels—waste from a global industry—into a high-tech material that could fight microbes. That's exactly what this study achieves, using nothing more than CO2 and light-activated nanoparticles.

The tomato processing industry churns out mountains of peels, seeds, and vascular tissues—residues that still hide valuable carotenoids like lycopene, a potent antioxidant. Traditionally, extracting these compounds means drowning the waste in organic solvents, a method that guzzles chemicals and leaves behind unusable biomass. But a greener path exists: supercritical carbon dioxide (scCO2). This technique uses CO2 in a state between gas and liquid to gently and efficiently pull lycopene from the peels, making the process both eco-friendly and economically attractive.

In this study, researchers optimized scCO2 extraction by testing different times, temperatures, and pressures. The sweet spot? Tomato peels treated at 50°C and 30 MPa for 2 hours yielded the highest lycopene amounts, as confirmed by UV-vis and HPLC analyses. Then came a twist: they conjugated this extracted lycopene with titanium dioxide nanoparticles (TiO2NPs) using a mild, green approach—no organic-solvent-derived carotenoids involved.

The result was a grain-like hybrid particle, 60–80 nm in size, with a remarkable 95.0 ± 2.1% loading efficiency of lycopene on the TiO2NPs. Characterization via FESEM, DLS, and other techniques showed that lycopene's presence controlled nanoparticle size and formed a protective organic layer. This TiO2NPs-lycopene conjugate could synergistically combine the antimicrobial power of TiO2 with lycopene's antioxidant properties, opening doors for pharmaceutical and nutraceutical applications. It's a win-win: valorizing waste and crafting a novel nanoplatform.

Key Points

• scCO2 extraction at 50°C, 30 MPa, 2h gives highest lycopene yield.
• 95.0 ± 2.1% lycopene loaded onto TiO2 nanoparticles via green method.
• First report of TiO2NPs-lycopene conjugate without organic-solvent carotenoids.