Rapid Characterization of Hops (Humulus lupulus) Using DART-MS and Chemometrics

Hops represent a key ingredient in beer and are often utilized to impart specific flavors. The popularity of hoppy beers (e.g., India Pale Ales) is raising expectations for stability, quality, and unique organoleptic properties of hops. Evaluation of hops is typically performed by sensory evaluation, requiring a trained human panel, and often yielding subjective results with limited throughput. Here, we present the use of ambient mass spectrometry (AMS) as an alternative approach to enable objective and rapid chemical fingerprinting of hops for quality screening reflective of sensory. Twelve hop samples were sourced from three different suppliers across four different farms located in Washington and Oregon (U.S.A.) over two growing seasons. The samples included three commercial cultivars, Cascade, Centennial, and Strata. The hop samples were extracted using an 80% ethanol solution and chemical fingerprints were acquired by Direct Analysis in Real Time Mass Spectrometry (DART-MS). The resulting data were used to train and validate predictive multivariate statistical models. Additionally, authentic standards of important hop compounds (hop alpha-acids, terpenes) were used to putatively annotate DART-MS signals and traditional sensory analysis was performed to support that the DART-MS data is reflective of sensory attributes. The results demonstrate the potential of this approach for rapid evaluation of hops quality. Ultimately, implementation of this tool could have applications for quality assurance programs and rapid phenotyping of hops by producers.