## 3 Results and Discussion
### Influence of the Oral Coating Formed by Peanut Lipid on Baijiu Aftertaste
After the formation of the mouth coating, spitting out the baijiu washes away part of the lipid and flavor substances, similarly to swallowing. To ensure sufficient compound-lipid contact in the oral cavity, the rinsing time of baijiu was 15 s, much longer than the actual consumption process. This would lead to a significant loss of highly hydrophobic compounds; however, their physicochemical properties allow them to persist in the mouth coating. The dynamic changes in the compounds at equidistant time nodes differed from the control group and did not change linearly, indicating that the release of baijiu flavor substances in the oral cavity was strongly and unevenly affected by the mouth coating forming by peanut lipid [20]. The influence of lipid on baijiu's aftertaste was mainly in the initial drinking stage. Without lipid, crucial aroma compounds of baijiu were rapidly consumed within the first 30 s, faster than that in the lipid-containing system. Compared with the lipid-free system, the reductions in ethyl heptanoate, ethyl lactate, nonanal, 2,3,5-trimethylpyrazine, ethyl octanoate, tetramethyl pyrazine, butyric acid, phenylacetaldehyde, nonanol, isovaleric acid, phenol, octanoic acid, p-cresol, and 4-ethylphenol in the lipid-coating system were no longer significant. Ethyl heptanoate, ethyl lactate, and ethyl octanoate are the key esters in baijiu [1]. In the experiment conducted on wine, an enzymatic hydrolysis reaction was believed to break down esters into corresponding acids and alcohols [23]. However, in baijiu, the high concentration of ethanol inactivates the enzyme, preventing the esterase reaction [16]. In this experiment, the decrease in esters were not significant. In both the lipid-containing system and the oil-free system, the compound intensities at 0 s had significant differences (\(t\)-test, \(p<0.05\)), but at 120 s, the release intensities of all compounds were no longer significant (\(t\)-test, multiple \(t\)-test, \(p>0.05\), Figure 5). This indicates that the lipid can reduce the release speed of the important compounds in baijiu and prolong the aftertaste's duration. The oral coating formed by peanut lipid can retain the compounds and slowly release them during the subsequent aftertaste. Figure 5: Intensity changes in bajiu aroma compound in the vivo experiment under the influence of mouth coating formed by peanut lipid. Moreover, the ethanol in baijiu could also be retained by mouth coating. Due to the Marangoni effect of ethanol, the presence of ethanol can sustain the continuous release of flavor substances in baijiu at a stable flow rate until they are consumed [14,15]. Given that ethanol exhibits surface activity, in the water (saliva)-ethanol solution, it preferentially resides at the air/liquid interface, thus diminishing the surface tension. During the dynamic process, the headspace becomes diluted, and the ethanol at the interface commences to evaporate. As the surface ethanol concentration declines, some depletion regions will emerge at the liquid surface with higher surface tension, promoting the molecules in the adjacent low surface tension regions to migrate towards the high surface tension regions. Driven by the surface tension gradient, the ethanol molecules in the lower layer ascend to supplement the liquid surface. Simultaneously, they carry the aroma molecules to escape into the gas phase at a constant rate. In the relevant dynamic equilibrium experiment, when the alcohol content of the system exceeds 6% ABV, the headspace concentration of the ethanol solution is higher than that of the aqueous solution with the same compound concentration. Moreover, its headspace concentration remains essentially stable as the ethanol concentration declines [24]. Consequently, even during the aftertaste stage, the continuous rinsing of the oral cavity by saliva, which dilutes the ethanol concentration, can still maintain the aftertaste intensity and duration of the baijiu aroma compounds to a certain degree.