Extraction conditions affecting supercritical fluid extraction (SFE) of lycopene from watermelon

Lycopene, a carotenoid linked to protection against certain forms of cancer, is found in produce such as papaya, red-fleshed tomatoes, grapefruit and watermelon. The preparation of a supercritical CO2 (SC-CO2) watermelon–lycopene extract could serve as a food grade source of this carotenoid. This study established preliminary conditions for enhancing SC-CO2 extraction of lycopene from watermelon. Freeze-dried watermelon was extracted with SC-CO2 and ethanol as an organic co-solvent. The lycopene concentration was determined by HPLC, with absorbance measured at 503 nm. In an initial set of experiments, the effects of extraction temperature (70–90 °C), pressure (20.7–41.4 MPa) and co-solvent ethanol addition (10–15%) were evaluated. A lycopene yield of 38 μg per gram of wet weight was obtained at 70 °C, 20.7 MPa, and 15% by volume ethanol. The extraction of fresh (non-freeze-dried) watermelon yielded 103 ± 6 μg lycopene per gram fresh fruit weight. Of the parameters tested, temperature had the most effect on lycopene yield. Thus, in another set of experiments, the temperature was varied from 60–75 °C at an extraction pressure of 20.7 MPa in the presence of 15% ethanol. Studies showed that freeze-dried watermelon flesh loses lycopene in storage. In accounting for lycopene storage losses, lycopene yields at 60 °C extraction temperature were 14% greater than those obtained at 70 °C.