Extraction of antioxidant compounds from blackberry (Rubus sp.) bagasse using supercritical CO2 assisted by ultrasound

• Supercritical CO2 extraction was applied to recover bioactive from blackberry residues.
• Ultrasound was applied during SFE to increase extraction rate and yield.
• Ethanol and water were used as cosolvents in SFE to enhance the recovery of antioxidants and anthocyanins from the blackberry bagasse.
• Four anthocyanins were identified and quantified in the extracts by UPLC.
• Images obtained by SEM showed changes caused by SFE and ultrasound in the sample's microstructure.

Supercritical carbon dioxide extraction (SFE) was performed to recover bioactive components from blackberry (Rubus sp.) industrial residues. Ultrasound was applied during the extractions in order to enhance rate and yield. Moreover, water and ethanol at different proportions were used as cosolvents to improve the extraction of polar compounds from the residues. The extraction global yields were measured at all performed conditions (pressure, temperature, ultrasound power and cosolvent). The extracts were evaluated in terms of their antioxidant activity, measured using two methods, phenolic content, monomeric anthocyanins, and anthocyanin profile. The application of ultrasound in SFE helped increasing the extraction rate at the beginning of the process, which could be observed on the extraction curves at 15 MPa, the lowest pressure applied. Scanning electron microscopy (FESEM) was used to analyze the blackberry bagasse undergoing SFE with and without ultrasounds and showed that ultrasound disturbs the cell walls, enhancing the release of the extractable compounds. The extracts have shown high antioxidant activity and phenolic contents when obtained at higher temperatures. Regarding anthocyanins, the use of water as cosolvent resulted in a significant increase. Four major anthocyanins were identified and quantified by ultra performance liquid chromatography (UPLC).

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