Pressurized liquid extraction of bioactive compounds from blackberry (Rubus fruticosus L.) residues: a comparison with conventional methods

• Pressurized liquids are able to recover phenolics and anthocyanins faster than conventional low pressure methods.
• Both temperature and solvent type had significant effect on the antioxidant activity of the PLE extracts.
• The recovery of phenolics is enhanced at high temperatures.
• Two major and two minor anthocyanins were identified in the PLE extracts and quantified through UHPLC.
• The PLE extract obtained with ethanol + water (1:1) at 100 °C had higher quality than those obtained by conventional methods.

Extracts with antioxidant compounds were obtained from residues of blackberries (Rubus fruticosus L.) through pressurized liquid extraction (PLE). The influence of solvent type (water, acidified water pH = 2.5, ethanol and ethanol + water 50% v:v) and temperature (60, 80 and 100 °C) on global yield (X0), total phenolics (TP), monomeric anthocyanins (MA) and antioxidant activity (AA) (by DPPH and ABTS) of the extracts was evaluated. Moreover, anthocyanins were identified and quantified by UHPLC-QToF-MS e UHPLC-UV-Vis, respectively. The best PLE condition was compared to conventional extractions (Soxhlet and maceration). Results showed positive influence of temperature on global yield, TP and AA. Ethanol + water as solvent at 100 °C was chosen as the best PLE condition, providing TP = 7.36 mgGAE/g fresh residue, MA = 1.02 mg C3GE/g fresh residue, AA = 76.03 μmol TE/g fresh residue and X0 = 6.33%. Excepting MA, all other results were over those of conventional extractions. Four anthocyanins were identified by UHPLC in the extracts, and their higher yields were achieved with acidified water as solvent at 60 and 80 °C. PLE has proved to be a promising alternative to recover bioactive compounds from blackberry residues, as well as other food by-products.