(E)-2-Nonenal in Beer with the Atomx and GC/MS SIM Detection

Significance of the Topic

Aged beer develops an off-flavor described as cardboard or papery, primarily due to the formation of (E)-2-nonenal. Monitoring this marker is critical for quality control in breweries and for ensuring product consistency over shelf life.

Objectives and Study Overview

This study evaluates the performance of the Teledyne Tekmar Atomx automated VOC preparation system using a modified soil method to extract and concentrate (E)-2-nonenal from beer. Detection and quantification are performed with GC/MS in Selected Ion Monitoring mode across five commercial pale lager lots.

Methodology and Instrumentation

Sample Preparation

• Beer samples: 10 mL degassed, spiked where indicated, with 6 g NaCl to enhance volatility.
• Standard solutions: (E)-2-nonenal in 5% ethanol at 0.27–5.4 ppb.

Atomx Soil Method

• Trap material: Tenax in Trap 1A.
• Purge/desorb cycle: 200 °C valve oven, 210 °C transfer line, purge at 70 °C for 10 min, desorb at 225 °C, bake at 230 °C.
• Flows: purge 25 mL/min, dry purge 50 mL/min, bake 200 mL/min.

GC/MS Settings

• Column: Rtx-VMS (20 m×0.18 mm, 1 µm film), He constant flow at 0.9 mL/min.
• Inlet/transfer line: 230 °C, split ratio 60:1.
• Oven program: 95 °C initial, ramp 3.5 °C/min to 145 °C, then 15 °C/min to 240 °C, 3 min hold.
• MS: source 230 °C, quad 150 °C; SIM ions at m/z 55, 70, 83, 96, 111; dwell 100 ms.

Key Results and Discussion

SIM total ion chromatograms of unspiked and spiked beer showed clear (E)-2-nonenal peaks with minimal interference. Quantified concentrations in five lots ranged from 0.082 to 0.463 ppb, demonstrating good sensitivity at mid-ppt levels. Triplicate analyses confirmed method reproducibility.

Benefits and Practical Applications

• High sensitivity and selectivity for trace-level off-flavor markers.
• Automated sample prep reduces manual steps and variability.
• Applicability in routine quality control in breweries.

Future Trends and Possibilities

Advancements may include integration with headspace SPME, real-time monitoring via portable GC/MS, and expansion to other volatile off-flavor compounds. Data analytics and predictive models could further enhance shelf-life forecasting.

Conclusion

The Teledyne Tekmar Atomx with a modified soil method coupled to GC/MS SIM delivers a robust approach for detecting (E)-2-nonenal in beer at sub-ppb levels. Its automation and sensitivity make it a valuable tool for maintaining flavor stability in brewing operations.

Reference

1. Scherer R., Wagner R., Kowalski C.H., Godoy H.T. (2010) Determination of (E)-2-nonenal in Brazilian beers using headspace SPME-GC-MS. Cienc. Tecnol. Aliment. 30(Suppl.1):161–165.