Recovery of Carotenoids via Novel Extraction Technologies for the Valorization of Tomato By-Products

Tomato processing residues—including peels, seeds, and pomace—are rich in bioactive compounds, such as lycopene, β-carotene, cutin, pectin, and antioxidants, yet are often underutilized. This study evaluates microwave-assisted extraction (MAE) and high-pressure-assisted extraction (HPAE) for the recovery of carotenoids from TP, compared to conventional extraction (CE) using ethyl acetate. Optimal MAE conditions (150 W, 50 °C, 20 min, solid/liquid ratio of 1:10 g/mL) yielded 592.5 mg carotenoids/kg dry weight (dw), exceeding CE yields (505.3 mg/kg dw), while significantly reducing extraction time (20 min vs. 120 min). By contrast, direct HPAE (650 MPa, ambient temperature, solid/liquid ratio of 1:10 g/mL) resulted in lower carotenoid yields (ca. 84 mg/kg dw), but when used as a pre-treatment followed by stirring for 24 h, HPAE enhanced carotenoids extractability to 277.0 mg/kg dw, recovering 55% of carotenoids extracted by CE. Bioaccessibility studies showed low lycopene bioaccessibility across all methods (3.9% for HPAE, 3.4% for MAE, and 1.6% for CE). Incorporation into oils significantly improved bioaccessibility, with olive pomace oil (OPO) achieving 28.1%, compared to 8.1% in corn oil (CO). Overall, MAE and HPAE (as pre-treatment) present efficient strategies that reduce solvent usage and processing time, though they still rely on organic solvents, while strategies to enhance bioaccessibility should further be explored for effective functional ingredient development.