Tomato Pomace Valorization: Green Solvent Evaluation, Microwave-Assisted Extraction Optimization, and Life-Cycle Assessment for Carotenoid Recovery

This study investigated the recovery of β-carotene (BC) and lycopene (LYC) from tomato processing waste (TPW) using microwave-assisted extraction (MAE) with green solvents. Sunflower oil (SO), olive oil, limonene, and several deep eutectic solvents were initially screened, after which SO and a capric acid–lauric acid deep eutectic solvent (CLA; 2:1 molar ratio) were selected for further optimization. The optimized MAE conditions for SO were 217 W for 4 min, yielding 2.82 ± 0.24 mg/100 g dry TPW of BC and 3.57 ± 0.27 mg/100 g of LYC, with an energy consumption of 0.014 kWh. For CLA, the selected conditions were 1800 W for 13 min, which resulted in significantly higher recoveries of BC (5.29 ± 0.84 mg/100 g) and LYC (9.80 ± 1.77 mg/100 g), although the energy consumption was higher (0.390 kWh). Vibrational micro-milling reduced the median particle size from approximately 303 to 66.8 μm and improved carotenoid recovery when combined with SO; however, it decreased recovery in CLA under more intensive MAE conditions. Life-cycle assessment (LCA) comparing optimal MAE extraction to conventional solvent extraction and ultrasound-assisted extraction showed that the CLA-based MAE process provided the most favorable overall balance between carotenoid recovery and environmental performance. Therefore, CLA can be recommended as the most effective solvent for the MAE recovery of BC and LYC from TPW, although further validation at a pilot scale and an assessment of solvent recovery are required.