Optimization of operating parameters for supercritical carbon dioxide extraction of lycopene by response surface methodology

An experimental design was developed to investigate the effect of operating temperature, operating pressure and extraction time on lycopene yield and extract antioxidant activity (IC50) during supercritical carbon dioxide extraction from tomato pomace. The statistical analysis of the experiment indicated that individual factors such as pressure and temperature, and interactive factors such as pressure with temperature and time had significant effects on lycopene yield. The central composite design showed that the polynomial regression models developed were in good agreement with the experimental results, with R2 of 0.97 and 0.94 for lycopene yield and extract antioxidant activity, respectively. The optimal condition for lycopene extraction within the experimental range of the variables studied was at 57 °C, 40 MPa, and 1.8 h. At this condition, the predicted amount of lycopene extracted was 28.64 mg in 100 g dried tomato pomace (corresponding to 93% lycopene recovery). In order to investigate the effect of experimental extraction condition on the antioxidant activity of the extract, IC50 was used as an index, which is the concentration that gives 50% reduction in the absorbance of the hydroxyl free radical. The analysis of the results relating to extract antioxidant activity showed that the individual effects of pressure and time, as well as their interactive effects, were significant. The statistical model gave the optimal point for antioxidant activity at 57 °C, 53 MPa, and 1.8 h of extraction, at which the value of 1/IC50 was 12.31 ml/mg (i.e. IC50 = 0.081 mg/ml).