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

Abstract

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 α-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.

Keywords:

• Hops
• Humulus lupulus L.
• mass spectrometry
• DART-MS
• chemometrics

Acknowledgements

We would like to thank all participating hop growers in Washington and Oregon for sampling, packaging, and shipping all samples for the two study years to Colorado State University; Wilson Machining in Fort Collins, CO for fabrication of DART-MS steel adapter; Odell Brewing Company for materials for sensory analysis and Odell Brewing Company staff for sensory analysis of all the hop samples.

Author contributions

Katie J. Nasiatka (Conceptualization, Funding Acquisition, Project Administration, Data Curation, Formal analysis, Investigation, Methodology, Original draft, Review and Editing), Harmonie M. Bettenhausen (Project Administration, Formal analysis, Investigation, Methodology, Original draft, Review and Editing), Jacqueline M. Chaparro (Conceptualization, Methodology, Review and Editing), Adam L. Heuberger (Conceptualization, Funding Acquisition, Methodology, Supervision, Review and Editing), Jessica E. Prenni (Conceptualization, Project Administration, Formal analysis, Methodology, Supervision, Original draft, Review and Editing)

Data availability

DART-MS data have been deposited to the MassIVE database (DOI: 10.25345/C5WS8HR32) with the identifier MSV000090797. The complete dataset can be accessed here: https://massive.ucsd.edu/ProteoSAFe/static/massive.jsp.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by Hop Research Council with partial support from the Odell Brewing Company.