High Speed Analysis of α-Acids and β-Acids in Hops

Significance of the topic

The rapid and reliable determination of α-acids, β-acids and iso-α-acids in hops is critical for beer quality control, flavor consistency and emerging health applications. Traditional HPLC analyses require ca. 30 minutes per run. A five-minute high-speed method enhances sample throughput, reduces solvent costs and supports timely decision-making in breweries and analytical laboratories.

Objectives and overview

The study aimed to develop and validate a high-speed HPLC method for simultaneous quantitation of α-acids, β-acids and iso-α-acids in hop pellets. Key goals included:

• Reducing analysis time to approximately five minutes per injection.
• Maintaining low system backpressure despite using methanol.
• Achieving accurate quantitation and high recovery rates for different hop varieties.

Methodology and instrumentation

• Instrument: Shimadzu Nexera XR UHPLC system.
• Column: Shim-pack Velox C18 core-shell (50 × 3.0 mm I.D., 1.8 µm).
• Mobile phases: A – 10 mmol/L sodium phosphate buffer (pH 2.6) with 0.2 mmol/L EDTA; B – methanol.
• Gradient: B conc. 80% at 0 min to 90% at 3 min, return to 80% by 5 min.
• Flow rate: 0.7 mL/min, column temperature 40 °C, injection volume 2 µL.
• Detection: UV at 314 nm (α- and β-acids); UV at 270 nm added for iso-α-acids.
• Sample preparation: 10 g hop pellets ground, extracted with methanol/diethyl ether in acidified conditions, phase separation, filtration through 0.22 µm.
• Standards: International Calibration Extract 4 dissolved in methanol; grouped into α- and β-acid homologues.

Main results and discussion

• Chromatographic separation achieved within five minutes with clear grouping of α-acids and β-acids peaks and baseline resolution.
• Maximum system backpressure ≈ 26 MPa, demonstrating the column’s ability to handle methanol without excessive pressure.
• Quantitation of two hop pellet samples (Hop A and Hop B) showed α-acid concentrations of 5.1% and 9.5%, β-acid concentrations of 14.3% and 24.0%, with recovery rates of 98–102% for α-acids and 90–97% for β-acids. Relative standard deviations were ≤ 2.4%.
• Simultaneous iso-α-acid analysis by spiking Hop A extract with 200 mg/L yielded a 99.7% recovery, validating the extended detection method at 270 nm and gradient adjustment to 60–100% B.

Benefits and practical applications

• High throughput through five-minute runs supports large-scale screening in brewing QA/QC.
• Core-shell column enables low backpressure and sustained column life even with high organic solvent content.
• Simultaneous multi-component analysis streamlines workflow and reduces instrument downtime.
• Robust quantitation and recovery make the method suitable for routine quality control of hops and hop extracts.

Future trends and potential applications

• Integration with mass spectrometry for enhanced specificity and trace-level detection of hop-derived compounds.
• Adoption of green solvents or aqueous-rich mobile phases to reduce environmental footprint.
• Development of on-line sample preparation or automated extraction modules to further accelerate analysis.
• Application to novel hop varieties and bioactive components for functional food and nutraceutical research.

Conclusion

The described five-minute HPLC method using a Shim-pack Velox C18 core-shell column on a Nexera XR system provides accurate, reproducible and high-throughput analysis of α-acids, β-acids and iso-α-acids in hops. It offers significant improvements over conventional protocols and is readily adaptable for routine brewery quality control and research purposes.

References

1. American Society of Brewing Chemists. ASBC Methods of Analysis, Hops-14.
2. European Brewery Convention. EBC Analytica, Method 7.7.