Optimization of lycopene extraction from tomato processing by-products with essential oils and effect of extract on oxidative stability of refined olive oil

Lycopene, a lipophilic antioxidant, was extracted from a Moroccan industrial tomato peels by-product using essential oils (EOs) as eco-friendly solvents. Peppermint essential oil (PEO), rosemary essential oil (REO), verbena essential oil (VEO), and thyme essential oil (TEO) were used as solvents. The highest extraction yield was obtained with REO. Response surface methodology (RSM) combined with a Box-Behnken design was used to maximize the extraction yield of lycopene. Optimal conditions were determined as follows: a solvent-to-material ratio of 35:1 (mL/g), a time of 60 min and a temperature of 60 °C. As a plant-based antioxidant, the lycopene extract was added to refined olive oil (ROO) to evaluate its oxidative stability during 5 months of storage at 40 °C. ROO enriched with lycopene extract at a concentration of 1 mg/g showed the lowest degree of oxidation, as evidenced by the lowest values of peroxide value, p-anisidine value, total oxidation value, free acidity, and specific extinction coefficients K₂₃₂ and K₂₇₀, compared to ROO containing 0.5 mg/g of lycopene extract and ROO containing 0.2 mg/g of BHA + BHT. The results of this study demonstrate that EOs are effective solvents for producing a value-added lycopene extract that can be an effective alternative to synthetic antioxidants. The study also highlights the synergistic effect of lycopene extract on ROO oxidation stability, shelf life and nutritional value.