Extrusion affects supercritical CO2 extraction of red pepper (Capsicum annuum L.) oleoresin

Carotenoids provide red colour and antioxidant properties in formulated foods. High-value, carotenoid-rich oleoresin can be extracted from red pepper using SuperCritical (SC) carbon dioxide (CO2). Densifying the solid substrate can overcome process limitations of batchwise operation to increase the extraction vessel load of red pepper. However, there is no information in literature on the effect of densifying treatments on the bioactive components of vegetable matrices. This work evaluated the effect of extrusion as a densification process on the yield and quality of SC–CO2–extracted red pepper oleoresin. A 23-factorial experimental design was used to study the effects of substrate pretreatment (control or extruded) and extraction temperature (40 or 60 °C) and pressure (30 or 50 MPa) on SC-CO2 extraction yield, and the extractable colour (ASTA units), carotenoid content, antioxidant activity (inhibition of a DPPH radical), and oxidative index (p-anisidine value) of the extracts. Extrusion had a significant (p ≤ 0.01) but negative effect on all responses. Independent of substrate pretreatment, SC-CO2 extraction yield and carotenoid yield where maximized at the extreme conditions of 60 °C and 50 MPa. The extractable colour and antioxidant activity correlated positively (p ≤ 0.05), and their oxidative index correlated negatively (p ≤ 0.05) with the carotenoid content of the SC-CO2 extracts.