## 3 Results
These higher carbon number ethyl esters are observed at much higher concentrations in the sauce aroma baijius. Furfural is also found in the sauce aroma samples along with succininic acid. Figure 2: PCA scores plot of distilleries using HS-SPME-GCMS data. Shaded areas are the 95% confidence regions. Expanded plots of the major congener areas of the \({}^{1}\)H NMR spectrum are presented in Figures 5 and 6. In Figure 5, we have compared the methyl signals showing lactic acid, 1-propanol, isopentanol, ethyl acetate, and acetic acid. Some peak shape distortion is observed in the peaks of samples 3 and 25, which appears to be a shimming issue. Figure 6 shows the ethyl ester region. 1-propanol appears to be the principal congener alcohol produced in most of the analyzed baijiu samples. This is quite different from Western fermentations of beer, wine, and cider, which have isopentanol as the major alcohol congener. In some baijiu samples, the distribution favors isopentanol (see sample 17 for example). Three carbon congeners such as propanol, propanoic acid and 1,3-propandiol are often a sign of extensive glycerol fermentation. The sauce aroma-style baijiu samples in this study contained higher concentrations of higher carbon number esters, such as butyric and caproate, as well as showed the presence of furfural. Figure 3: PCA scores plot of %ABV using FTIR data. Group 1—above 55%, Group 2—50–55%, Group 3—45–50%, Group 4—40–45%, Group 5—below 40%. Shaded areas are the 95% confidence regions. Utilizing the qNMR calculations described previously, the concentrations of ethanol and the major congeners were calculated for a sub-set of 10 of the baijiu samples, and these parameters are presented in Table 2. The table also contains the location and multiplicity of the peaks that were integrated to perform the calculations. It is noted that some of the baijiu samples (e.g., sample 10) do not contain observable amounts of congeners. This is often a sign of counterfeit spirits that are derived from pure ethanol [29]. Figure 7 shows a superimposed spectrum of suspected counterfeit sample 10 (green) with typical baijiu sample 3 (red). It is obvious to the observer that only ethanol is observed in sample 10, with congeners seen to be missing. Two of the thirty samples analyzed in this study showed no congeners to be present in the product. SPME-GCMS also identified the same two samples as containing very low concentrations of congeners. Figure 4: \({}^{1}\)H NMR spectrum of a typical baijiu sample (sample 3, manufacturer 1, Sauce Aroma) showing the assignment of various congeners that are readily observed and quantified. The numbered assignments are as follows: 1. lactic acid; 2. ethyl lactate; 3. ethyl acetate; 4. ethanol (intense signals off scale); 5. furfural; 6. methanol; 7. acetaldehyde; 8. acetic acid; 9. 1-propanol; 10. isopentanol; 11. maleic acid (internal quantitation standard); 12. water—suppressed with pre-saturation and not shown; 13. higher esters CH\({}_{2}\) adjacent to carboxyl—butyric, caproic etc. ; 13C. \({}^{13}\)C satellites arising from the coupling of intense ethanol signals with 1.1% of protons in the sample. Figure 8 shows the comparison of the ethanol concentrations obtained by qNMR with the stated label values, showing an excellent correlation between the two (R\({}^{2}\) = 0.9939). With confidence in the qNMR calculation and the fact that the NMR technique directly observes and quantifies the ethanol NMR signals in the spectrum, we confirmed that 27 of the 30 baijiu samples had the correct ethanol content on the label to a standard deviation of 0.6 %ABV. However, 3 out of 30 samples had ethanol values that were considerably different to that stated on the label. Two samples from one distiller were 7% higher than stated on the label, and another distiller had a sample that was 11% lower than stated.