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

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.

Determination of 2-Pentanol Enantiomers via Chiral GC-MS and Its Sensory Evaluation in Baijiu

“…Soy sauce aroma-type Baijiu (SSB), strong aroma-type Baijiu (STB), light aroma-type Baijiu (LTB), and rice aroma-type Baijiu (RTB) are the four basic aroma types, which are popular among consumers because of their unique flavors [ 24 , 25 ]. 2-Pentanol, also known as secondary amyl alcohol, is considered to be an important volatile substance in Moutai [ 26 ], Yanghe Daqu [ 27 ], Wuliangye [ 28 ], and red wine [ 29 ], etc. ; it has an asymmetric chiral carbon atom and exists in two different stereoisomers, as shown in Figure 1 , and its enantiomers are widely used in medicine, such as (S) -2-pentanol is a key chiral intermediate required for the synthesis of several potential anti-Alzheimer’s disease drugs [ 30 ].…”

A Miniature Four-Channel Ion Trap Array Based on Non-silicon MEMS Technology

“…Mass spectrometry is an important material analysis method nowadays. It has been widely used in many research fields, such as chemical analysis, drug metabolism, clinical medicine, environmental protection, food safety, anti-terrorism, public emergencies, and military technology [ 1 , 2 , 3 , 4 , 5 ]. Although the conventional desktop mass spectrometer has a relatively high technical maturity, it has the disadvantages of large size, high power consumption, and high price, which cannot meet the growing demand.…”

Comment on Hu et al. Determination of 2-Pentanol Enantiomers via Chiral GC-MS and Its Sensory Evaluation in Baijiu. Foods 2022, 11, 2584

“…Some of the papers devoted to an GC-MS analysis of volatile organic compounds, including 2-pentanol, contain information that the compounds were identified by comparing their mass spectra with the mass spectra in the database [ 11 , 12 , 13 , 14 , 15 ], and sometimes with the similarity indexes [ 14 , 16 ], retention indexes [ 16 , 17 , 18 ] or exemplary ions that have been mentioned [ 15 ], whereas sometimes no data have been provided [ 19 ]. In my opinion, at least a few exemplary mass spectra should be always provided, e.g., in the Supplementary Materials.…”