Determination of Linalool in Different Hop Varieties Using a New Method Based on Fluidized-Bed Extraction with Gas Chromatographic-Mass Spectrometric Detection

Abstract

Linalool, an important substance in hoppy, aromatic beer, is one of the most aromatic components of essential oils in hops. Linalool concentration, among those of other substances, could be used to distinguish among hops varieties. As such, an effective, repeatable, and high-throughput method is required; a new method based on fluidized-bed extraction combined with detection by gas chromatography–mass spectrometry was developed and is presented in this study. This method is faster than the reference method, which uses steam distillation; it also reduces the possibility of thermal changes. Because this method saves organic solvent, energy, and sample amount, it can be considered a green method. Good repeatability of the method (8.0 mg/kg) was achieved with 3-hepten-1-ol as an internal standard. The detection limit of linalool is 1.0 mg/kg, and the limit of quantification is 3.5 mg/kg. Good agreement was achieved between the results of the new and steam-distillation methods. In addition, 59 samples of hops from four important Czech varieties (Agnus, Premiant, Saaz, and Sládek) from the 2013 harvest were analyzed, and the content of linalool was correlated with the content of bitter acids in xyz 3-D projection; four separate and clearly limited clusters that corresponded to the four tested varieties were obtained.