Extraction of phenolic compounds from dry and fermented orange pomace using supercritical CO2 and cosolvents

This work investigated the supercritical fluid extraction (SFE) of phenolic compounds from the pomace generated in the industrial processing of orange (Citrus sinensis) juice in Brazil. The effect of the biotransformation of the pomace, performed through solid-state fermentation using Paecilomyces variotii, in the phenolic content and antioxidant activity of the extracts was also evaluated. SFE was carried out at pressures of 15, 25 and 35 MPa and temperatures of 40, 50 and 60 °C, using pure ethanol and ethanol:water (9:1 v/v) as cosolvents. The extracts were evaluated in terms of global extraction yield, total phenolic content (TPC), phenolic profile by HPLC, and antioxidant activity through DPPH and ORAC assays. Additionally, a low pressure extraction was performed (Soxhlet) for comparison to SFE, using ethanol as solvent. The results of SFE showed that high pressures improved the global extraction yield, which ranged from 2.01 to 2.62%, and TPC (18-21.8 mg GAE/g dry extract). Nevertheless, the increase of pressure decreased the antioxidant activity of the extracts. The use of ethanol 90% as cosolvent enhanced the extraction of antioxidant compounds. The biotransformation process improved the TPC and provided extracts with higher antioxidant activities by both DPPH and ORAC assays.