Discrimination of Red Wines with a Gas-Sensor Array Based on a Surface-Acoustic-Wave Technique.

Lin Lin,Yao Yao,Ke Ke

doi:10.3390/mi10110725

Abstract

We applied a thermal-desorption gas-chromatograph mass-spectrometer (TD-GC–MS) system to identify the marker volatile organic compounds (VOCs) in the aroma of red wine. After obtaining the marker VOC, we utilized surface acoustic waves (SAWs) to develop a highly sensitive sensing system as ‘electronic nose’ to detect these marker VOC. The SAW chips were fabricated on a LiNbO3 substrate with a lithographic process. We coated sensing polymers on the sensing area to adsorb the marker VOC in a sample gas. The adsorption of the marker VOC altered the velocity of the SAW according to a mass-loading effect, causing a frequency decrease. This experiment was conducted with wines of three grape varieties—cabernet sauvignon, merlot and black queen. According to the results of TD-GC–MS, the King brand of red wine is likely to have unique VOC, which are 2-pentanone, dimethyl disulfide, 2-methylpropyl acetate and 2-pentanol; Blue Nun-1 probably has a special VOC such as 2,3-butanedione. We hence used a SAW sensor array to detect the aroma of red wines and to distinguish their components by their frequency shift. The results show that the use of polyvinyl butyral (PVB) as a detecting material can distinguish Blue Nun-2 from the others and the use of polyvinyl alcohol (PVA) can distinguish King from the others. We conducted random tests to prove the accuracy and the reliability of our SAW sensors.

Highlights

Red wine has its own unique aroma; according to some authorities 85% of the taste of red wine is sensed by olfaction
After determining the marker volatile organic compounds (VOCs), we used a surface acoustic waves (SAWs) sensing system coated with polyvinyl butyral (PVB), polyvinyl alcohol (PVA), PS, PNVP, P4VP and polymethyl methacrylate (PMMA) on the sensing area to detect the red wine
Because the marker VOCs, which could discriminate King from Blue Nun-2 and Blue Nun-1, were highly polar compounds, we selected highly polar polymers such as PVA, PNVP and P4VP that have a strong affinity based on the van der Waals force

Summary

Introduction

Red wine has its own unique aroma; according to some authorities 85% of the taste of red wine is sensed by olfaction. We know that these VOCs determine the characteristics of red wine aroma; some VOCs, such as vanillin or β damascenone or (E)-β-methyl-γ-octalactone, have a positive correlation with a pleasant aroma, whereas VOC such as 4-ethyl- and vinyl-phenols or 3-(methylthio)-1-propanol or phenylacetaldehyde have a negative correlation, being associated with an unfavorable odor [1]. We can utilize these unique VOC in the aroma of red wine for differentiation and to ensure the accuracy of information such as the origin and the grape variety to protect consumers. We chose the most common grape varieties (cabernet sauvignon and merlot) and a unique variety (black queen) of Taiwan to undertake an analysis of their aromas

Methods

Results

Conclusion