High Speed Analysis of α-Acids and β-Acids in Hops by using UHPLC

Significance of the Topic

Accurate quantification of hop-derived α-acids and β-acids is essential for controlling beer bitterness and flavor consistency. Conventional spectrophotometric IBU assays may overestimate bitterness in complex matrices, while traditional HPLC methods provide specificity at the expense of analysis time. A high-speed UHPLC approach can enhance throughput and reliability in brewery quality control and hop profiling.

Objectives and Study Overview

The study aimed to develop and validate a rapid UHPLC method for simultaneous determination of α-acids and β-acids in hop samples, compare results with conventional HPLC and standard IBU measurements, and demonstrate applicability to beer and hop analysis following EBC and ASBC guidelines.

Methodology and Instrumentation Used

• Sample Preparation
  Beers were processed according to EBC 9.47 for iso-α-acid analysis; hop pellets were extracted using standardized solvents and spiked for recovery tests.
• Analytical Methods
  Iso-α-acids, α-acids, and humulinones in beer were separated using standard HPLC (45 min runtime) versus UHPLC (5 min runtime) with EDTA addition to improve peak shape. IBU was determined by solvent extraction and UV detection at 275 nm per ASBC Beer-23A. Hop α/β-acids were quantified under UHPLC conditions aligned with EBC 7.7 and ASBC Hops-14.
• Instrumentation
  
  • Shimadzu Nexera XR UHPLC system
  • Shimadzu UV-1900i UV-Vis spectrophotometer
• Standards and Calibration
  Reference materials included DCHA-Iso, ICS-I4, International Calibration Extract 4, and DCHA-Humulinones. Calibration followed official EBC and ASBC protocols.

Main Results and Discussion

• Analysis Time Reduction
  UHPLC reduced runtime from 45 min to approximately 5 min without requiring pH adjustments.
• Chromatographic Performance
  EDTA in the mobile phase enhanced the resolution of iso-α-acid isomers. Hop α/β-acid homologues were clearly separated.
• Correlation with IBU and HPLC Data
  UHPLC quantification of hop acids correlated closely with conventional HPLC and IBU values; IPA beers displayed elevated α-acid and humulinone content, consistent with their characteristic bitterness.
• Method Precision and Recovery
  Spike-and-recovery tests (n=6) yielded acceptable accuracy and repeatability, confirming method robustness.

Benefits and Practical Applications

The high-speed UHPLC method offers significant advantages for brewery quality control and hop breeding programs:

• Rapid throughput for routine analysis
• Enhanced specificity and reduced interference compared to spectrophotometric assays
• Elimination of pH meter requirement simplifies mobile phase preparation
• Applicability to a wide range of beer styles and raw hop materials

Future Trends and Potential Uses

• Integration of UHPLC with mass spectrometry for structural profiling of hop compounds
• Automation and real-time monitoring of brewing processes
• Development of standardized high-speed protocols across breweries
• Expansion to other brewing ingredients and flavor-active compounds

Conclusion

A rapid UHPLC approach using Shimadzu Nexera XR enables accurate, high-throughput analysis of hop α-acids and β-acids, outperforming traditional HPLC and IBU methods in speed and selectivity. This technique supports improved quality control, flavor consistency, and efficient resource utilization in brewing and hop research.

Reference

• Hirao Y., Uchida A. Shimadzu Corporation: High Speed Analysis of α-Acids and β-Acids in Hops by UHPLC
• European Brewery Convention (EBC) Methods 7.7, 9.47
• American Society of Brewing Chemists (ASBC) Beer-23A, Hops-14