The effects of various parameters of supercritical carbon dioxide (SC-CO2) fluid extractions of tomato
skins on the extraction yields and antioxidant activities of lycopene-rich extracts were investigated. A
Box–Behnken design was applied to study the effects of three independent variables (temperature ranging
from 40 to 100 C, pressure ranging from 20 to 40 MPa, and flow rate ranging from 1.0 to 2.0 mL/min)
on lycopene yield. The model showed good agreement with the experimental results, by the coefficient of
determination (r2 = 0.9834). Temperature, pressure, and the quadratic term for the temperature of SCCO2
extraction were large significantly positive factors affecting lycopene yield (P < 0.05). The maximum
total lycopene content of 31.25 lg/g of raw tomato was extracted at the highest temperature of 100 C,
40 MPa and 1.5 mL/min. TEAC assay was applied to assess the antioxidant activity of lycopene-rich
extracts from SC-CO2 fluid extraction. The effects of SC-CO2 fluid extraction parameters on the antioxidant
activities of the extracts differed with the yield. For each unit of lycopene extract, the antioxidant
activity level was constant below 70 C, but then gradually decreased above 70 C due to isomerization
occurring as a result of the higher temperature. The ratio of all-trans-lycopene to the cis-isomers changed
from 1.70 to 1.32 when the operating temperature was adjusted from 40 to 100 C, indicating an
increased bioavailability due to the generation of the cis-isomers. No significant effects of pressure or
flow rate of SC-CO2 fluid extraction on the antioxidant activity were observed.