Supercritical fluid-assisted extraction of hop cone residue from craft breweries

Abstract

This study aimed to use supercritical fluid-assisted extraction in hop cone residue from craft breweries and define the best extraction parameters. Yield, compounds extracted, in vitro chemical and cell-based antioxidant activities, and antimicrobial and cytotoxic potentials were evaluated. The variables studied were temperature (40–60 °C), pressure (10–20 MPa), and ethanol percentage as co-solvent (5–10%) using a Taguchi experimental design (11 runs). The extracts showed inhibitory action towards Gram-positive and Gram-negative bacteria, mainly Proteus mirabilis and Enterococcus faecalis (MICs = 5–10 mg/mL). Furthermore, up to the maximum tested concentration (400 μg/mL), the extracts showed no hepatotoxicity on a healthy porcine liver cell line (PLP2), indicating safety for food and pharmacological applications. Lower temperatures (40 °C), pressures (10 MPa), and ethanol percentages (5%) resulted in higher concentrations of some compounds (alpha-copaene, γ-elemene, γ-muurolene, α-muurolene, caryophyllene oxide) and higher antioxidant activity in cell-based assays, but lower yields. At the same time, lower temperatures (40 °C) and pressures (10 MPa) but higher ethanol percentages (10%) resulted in higher concentrations of other compounds (nerolidyl acetate, linalyl isobutyrate, α-acorenol, and geranyl isovalerate) and increased antioxidant activity in chemical systems. Our results support that the hop cone residue can be used to obtain supercritical fluid-assisted extracts with biological potentialities that might virtually be upcycled into multifunctional ingredients for the food and pharmacological industries. Using 40 °C, 10 MPa, and 5 or 10% ethanol percentage as process parameters is advisable.