Comparison of aromatic compounds in two different red wines by using GC-High resolution TOFMS with the integrated data analysis of msFineAnalysis AI [GC-TOFMS Application]

Introduction

Experiment

Two typical red wines, produced in Bordeaux and Bourgogne, which are generally available in a supermarkets were used as test samples. 2 mL portion of the wine samples were added to 15mL glass vial and immediately sealed. The SPME fiber was inserted into the headspace of the glass vial and the fiber was exposed for 20 min at room temperature. All extracted compounds in the SPME fiber were introduced into GC by heating at injection port of GC for 1min. The details of measurement condition were shown in Table 1. To use the differential analysis functionality, each sample was measured for three times using EI ionization. Then those measurement results were applied to msFineAnalysis AI (JEOL Ltd.) together with the measurement results by PI ionization.

Table 1. Measurement condition

Results

Total Ion Current Chromatograms (TICCs) obtained as a result of measuring the aromatic components of Bordeaux and Bourgogne wines by EI ionization are shown in Fig.1. In addition, the volcano plot obtained as a result of performing a difference analysis using Bordeaux wine as Sample A (blue) and Bourgogne wine as Sample B (red) is shown in Fig.2. In the volcano plot of msFineAnalysis AI software, the horizontal axis represents the intensity ratio between two samples (Log2(B/A)), and the vertical axis represents statistical reproducibility (-log10(p-value)). By using this volcano plot, it becomes easy to understand the difference in components. The plots in the area with a blue background shown in Fig. 2 are characteristically detected peaks in Sample A, and conversely, those with a red background are the characteristically peaks in Sample B.

Table 2. Integrated qualitative analysis results for the characteristic compounds for Sample A (Bordeaux)and Sample B (Bourgogne)

The characteristic compounds in each sample (Bordeaux : Sample A and Bourgogne : Sample B) were identified and listed in Table 2. Totally 14 compounds (9 from Bordeaux, 5 from Bourgogne) were identified. Concerning 8 of 14 compounds, the molecular ions were identified, and the exact m/z values of those molecular ions agreed with the exact m/z values of the estimated compounds. In addition, the EI fragment coverage values for those compounds that are calculated from the relationship between the elemental composition of fragment ions and those of molecular ion were also high values. This means the validity of the compound identification is much higher than by simple library search alone.
It is known that several 'carboxylic acid esters' are the typical aromatic compounds that characterized the aroma of wine. Many kinds of methyl and/or ethyl esters of low fatty acids were detected from both of Bordeaux and Bourgogne wine. This means that the esters of low fatty acids strongly contribute the aroma of wines.
The comparison of TICC by EI and PI for Hexanoic acid ethyl ester that was detected from both of Bordeaux and Bourgogne wines is shown in Fig 3. The position of the Hexanoic acid ethyl ester in the volcano plot is also shown in Fig.4. By using the differential analysis functionality of msFineAnalysis, the detailed data analysis and confirming information is available for each peak.

It is interesting to note that esters of fatty acids with a relatively large number of carbon atoms were detected as the characteristic compounds of Bourgogne wine.
Several compounds such as Propylene Glycol and Methyl salicylate in Bordeaux wines and 3,4,4a,5,6,7-hexahydro-1,1,4a-trimethyl-2(1H)-Naphthalenone in Bourgogne wines were detected as characteristic compounds for only one of the two types of wine.
The TICC's of EI and PI measurements for 3,4,4a,5,6,7-hexahydro-1,1,4a-trimethyl-2(1H)-Naphthalenone is shown in Fig.5.　Although the peak corresponding to 3,4,4a,5,6,7-hexahydro-1,1,4a-trimethyl-2(1H)-Naphthalenone was detected as a shoulder peak beside of a huge peak, it was clearly detected using the chromatographic deconvolution functionality of msFineAnalysis AI. The mass spectra of 3,4,4a,5,6,7-hexahydro-1,1,4a-trimethyl-2(1H)-Naphthalenone measured by EI and PI is shown Fig. 6.

In total 14 compounds were found as characteristic compounds from only Bordeaux and only Bourgogne wine in this study. It is suggested that those compounds contribute the characteristic aroma and taste for both wines.

Conclusion

In this MSTips, we introduced an example of difference analysis by using msFineAnalysis AI concerning aroma components in wines from different production areas.
By using msFineAnalysis AI, qualitative analysis for GC-TOFMS is expected to be more accurate and efficient.

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