Selective extraction of bitter acids and volatile compounds from hops (Humulus lupulus L.) using sub- and supercritical CO2 and subcritical R134a

Abstract

This study investigates the extraction of bioactive compounds from Polaris variety hops using pressurized fluid systems with carbon dioxide (CO₂) and 1,1,1,2-tetrafluoroethane (R134a) as solvents. The effect of hop particle size on extraction yield was evaluated under subcritical CO₂ conditions (100 bar, 10 °C), with kinetic modeling via the Weibull equation. Optimal yields were observed with particles between 500 and 1000 μm. R134a extraction employed a central composite design to examine temperature and pressure effects, with temperature showing a significant influence on yield. Chemical characterization included volatile organic compounds (VOCs), bitter acids (α- and β-acids), and total phenolic content. Subcritical CO₂ favored selective extraction of α-acids and monoterpenes, while supercritical conditions enhanced the solubility of less volatile compounds. R134a demonstrated selectivity for moderately polar compounds, such as esters and alcohols, with temperature-dependent efficiency.