Ethanol content in wine by nearinfrared spectroscopy

Importance of the topic

The accurate determination of ethanol content in wine is essential for process control during fermentation, ensuring product quality, and meeting regulatory requirements. Traditional gas chromatography methods, while accurate, are time-consuming, labor-intensive, and require chemical reagents.

Objectives and study overview

This application note aimed to develop a rapid, reagent-free method using near-infrared spectroscopy (NIRS) to quantify ethanol concentration in red and white wine. The goal was to establish a robust calibration model that correlates NIR spectra with reference values obtained by gas chromatography.

Methodology and instrumentation

The analysis was performed on an OMNIS NIR Analyzer Liquid operating in the 1000–2250 nm range in transmission mode. Samples were pumped through a 2 mm quartz flow-through cell using the OMNIS Sample Robot S. Data acquisition and quantitative model development were completed with OMNIS Software.

• OMNIS NIR Analyzer Liquid (1000–2250 nm)
• 2 mm NIRS quartz flow-through cell
• OMNIS Sample Robot S with built-in peristaltic pump
• OMNIS Software for spectral acquisition and chemometric modeling

Main results and discussion

The NIR spectra of various wine samples were used to build a predictive calibration via a leave-one-out validation approach. The model demonstrated excellent performance with a calibration coefficient (R2) of 0.995, a standard error of calibration (SEC) of 0.080 % vol, and a standard error of cross-validation (SECV) of 0.082 % vol, indicating high accuracy and repeatability in ethanol determination.

Benefits and practical applications of the method

This NIRS-based approach offers several advantages over classical methods:

• Rapid analysis in under 10 seconds without sample preparation
• Chemical‐free operation reduces consumable costs and waste
• Automatable workflow with unattended measurement of up to 175 samples
• Integration capability for at-line monitoring during fermentation and quality control laboratories

Future trends and opportunities

Advancements in NIR instrumentation and chemometric algorithms will further improve sensitivity and robustness. Portable and inline NIR sensors may enable real-time vineyard monitoring. Integration with artificial intelligence and IoT platforms could facilitate predictive quality control and process optimization across the wine industry.

Conclusion

The presented NIR spectroscopy method delivers a fast, accurate, and cost-effective solution for ethanol analysis in wine. Implementation of the OMNIS platform streamlines operations, reduces reliance on consumables, and supports high-throughput automated workflows.

Reference

• Metrohm Application Note AN-NIR-147: Ethanol content in wine by near-infrared spectroscopy