Determination of Trans-2-Nonenal in Barley Grain, Malt and Beer

Significance of the Topic

trans-2-Nonenal is a key aldehyde responsible for rancid butter flavor in stored beer, impacting sensory quality and consumer acceptance. Reliable quantification of this compound in brewing raw materials and final products is crucial for quality control and shelf-life assessment.

Objectives and Study Overview

• Optimize and implement an automated headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC) method for trans-2-nonenal determination in barley, malt, and beer.
• Evaluate five SPME fiber coatings to identify the most efficient extraction phase.

Methodology and Instrumentation

HS-SPME parameters were optimized using a 10 µg standard in water: 100 µm PDMS, 65 µm PDMS/DVB, 85 µm CAR/PDMS, 50/30 µm DVB/CAR/PDMS and 85 µm PA fibers were tested. Extraction was performed at 60 °C for 20 minutes with 1.5 g NaCl, followed by GC-MS identification and automated GC-FID quantification.

Used Instrumentation

• Gas chromatograph Thermo Scientific Trace GC Ultra with FID and MS detectors
• Supelcowax capillary column (30 m × 0.25 mm, 0.25 µm)
• Automated sampler CombiPal (CTC Analytics)
• Laboratory mill, cooled centrifuge, shaker

Main Results and Discussion

• The PDMS/DVB fiber achieved the highest extraction efficiency for trans-2-nonenal.
• Calibration was linear from 0.03 to 3.4 µg L⁻¹ (r = 0.9998); LOD and LOQ for beer were 5 × 10⁻³ and 15 × 10⁻³ µg L⁻¹, respectively.
• Trans-2-nonenal levels in barley ranged 0.28–3.06 µg kg⁻¹; in malt 8.90–38.54 µg kg⁻¹; in beers 1.01–3.44 µg L⁻¹ in dispensed beer, 1.06–4.02 µg L⁻¹ in pale lager, and 3.39–20.28 µg L⁻¹ in nonalcoholic beer.

Practical Benefits and Applications

The automated HS-SPME-GC-FID method offers rapid, sensitive, and reproducible quantification of trans-2-nonenal, supporting quality assurance in brewing, raw material screening, and storage stability monitoring.

Future Trends and Opportunities

• Integration with high-resolution and tandem mass spectrometry for enhanced selectivity.
• Development of on-fiber derivatization techniques to improve detection limits.
• Automation and miniaturization for high-throughput screening in industrial settings.

Conclusion

The validated method using PDMS/DVB fiber provides a robust analytical tool for monitoring trans-2-nonenal in barley, malt, and beer, enabling effective sensory quality control and shelf-life studies.

Reference

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