Rapid extraction of xanthohumol, α- and β-acids from spent hops using pressurized liquids and supercritical fluids

Abstract

The recovery of bioactive compounds from spent hops from dry-hopping was obtained by pressurized liquid (PLE) and supercritical fluids (SFE) with cosolvent. PLE was performed at 10 MPa, with 50, 75, and 100 wt% ethanol in water at 70, 90, and 110 °C. SFE was performed using carbon dioxide with 10 wt% ethanol at 15, 25, and 35 MPa, and 40, 50, and 60 °C. The extracts were evaluated in terms of global yield, total reducing capacity (TRC), antioxidant capacity (ORAC), and content of target compounds. Temperature had little influence on the PLE results, except for α-acids, which were converted to iso-α-acids at 110 °C. The solvent composition impacted TRC, with 75 % ethanol being more efficient in extracting phenolic compounds (30.31 ± 2.86 mg GAE/g spent hops at 110 °C). The kinetics of PLE showed that most compounds are rapidly extracted in the first 6 min. In SFE, pressure was the most important factor, with 25 MPa and 60 °C being the most effective condition (36.21 ± 1.77 % global yield). Higher pressures and temperatures led to the co-extraction of undesired compounds, reducing α- and β-acid yields. The kinetics SFE curves exhibited a similar pattern to those of PLE, revealing that most compounds were quickly recovered in the first 6–7 min. Spent hops from dry-hopping are a promising source of xanthohumol and α- and β-acids, with high antioxidant capacity and potential applications in the food, cosmetic, and pharmaceutical industries.