Quantifying Ethanol Content in Beer

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Researchers from the Republic of North Macedonia and Kosovo have demonstrated that Fourier transform infrared (FT-IR) spectroscopy combined with chemometric modeling can accurately quantify ethanol in beer, offering breweries a faster, non-destructive alternative to conventional gas chromatography methods. The findings were published in the journal European Food Research and Technology.¹

Ethanol content is a critical quality attribute in beer production.^1,2 It is a colorless liquid and a primary end-product of anaerobic fermentation reactions.² Because of its importance in the beer industry, producers are interested in using methods that can provide accurate alcohol content measurements.

In this study, the researchers used attenuated total reflectance FT-IR (ATR-FTIR) spectroscopy to analyze beer samples across four mid-infrared (MIR) spectral regions between 960 and 1700 cm⁻¹.¹ Their findings revealed that the 1200–1490 cm⁻¹ interval provided the most reliable ethanol predictions, with minimal interference from the complex beer matrix.¹ For comparison, the researchers looked at the results from this region that were obtained by using gas chromatography–flame ionization detection (GC-FID) and found that the results obtained using ATR-FTIR spectroscopy closely matched with those obtained by GC-FID.¹

In addition, the researchers tested a new way to improve predictive performance. Through using partial least squares regression (PLSR) models, the team incorporated different spectral preprocessing strategies and evaluated which method performed better. The best-performing model applied a first-derivative transformation with Savitzky–Golay smoothing using a second-order polynomial and a 21-point window.¹ This configuration achieved a coefficient of determination (R²) of 0.978, with a root mean square error of calibration of 0.578% (v/v) and a prediction error of 0.36% (v/v).¹

Apart from accuracy, the method showed strong analytical sensitivity, with a limit of detection of 0.021% and a limit of quantification of 0.071% (v/v).¹ According to the authors, these performance metrics indicate that FTIR-PLSR might be suitable for routine ethanol analysis in beer.

“The findings confirm that FTIR-PLSR is a suitable and efficient alternative to conventional chromatographic techniques for routine ethanol monitoring in the brewing industry,” the authors wrote in their study.¹

References

1. Rexhepi, F.; Blazhekovikj-Dimovska, D.; Hyseni, B. et al. Rapid and Non-destructive Ethanol Quantification in Beer Using FTIR-ATR Spectroscopy and PLSR Modeling. Eur. Food Res. Technol. 2026, 252 (15). DOI: 10.1007/s00217-025-04975-9
2. Craft Beer & Brewing, Ethanol. Beer and Brewing. Available at: https://www.beerandbrewing.com/dictionary/BVYow0MwFL (accessed 2026-02-12).