Application of Response Surface Methodology to Supercritical CO2 Extraction: Case Study on Coextraction of Carotenoids and Oil from Rosehip Shells and Seeds

Response surface methodology (RSM) is an experimental strategy widely used as a research tool in investigation. We reviewed 89 papers that used RSM to study the extraction of oils or minor lipids, using supercritical (SC) CO₂, and observed that most of these studies have not contributed to an understanding of the extraction phenomenon, by neglecting prior knowledge on mass transfer or equilibrium relationships. We used the extraction of carotenoids from rosehip shells and oil from the seeds, as a case study to illustrate an improved strategy to apply RSM to oil-aided SC-CO₂ extraction of high-molecular-weight nonpolar solutes, such as carotenoids. We selected the temperature and density to characterize the effect of solvent conditions, the specific CO₂ consumption to characterize the interaction of solvent time and solvent power, and the percentage of seeds in the composite substrate to characterize the cosolvent effect of the oil. A rotatable central composite design was applied sequentially in three blocks, where the third block allowed incorporating quadratic coefficients to adequately describe the non-linear behavior of the responses.