## 3 Results and Analysis
### Sensory Analysis of Koumiss in Different Regions
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**VOCs**} & \multirow{2}{*}{**Cas**} & \multirow{2}{*}{**Threshold**} & \multicolumn{3}{c}{**OVA**} \\ \cline{3-6}  & & & **YL** & **TC** & **ALTw** & **ALTe** \\ \hline Ethyl caprate & 110-38-3 & 0.02 e & 1446.87 \(\pm\) 120.65 a & 723.31 \(\pm\) 83.19 b & 221.12 \(\pm\) 16.59 c & 112.28 \(\pm\) 77.99 c \\ Ethyl caprylate & 106-32-1 & 0.022 g & 1012.47 \(\pm\) 122.04 a & 689.41 \(\pm\) 105.23 b & 175.70 \(\pm\) 73.23 c & 131.04 \(\pm\) 52.17 c \\ Ethyl laurate & 106-33-2 & 3.5 f & 223.23 \(\pm\) 0.26 a & 1.47 \(\pm\) 0.09 b & 0.17 \(\pm\) 0.09 c & 0.08 \(\pm\) 0.07 c \\ Octanoic acid & 124-07-2 & 0.5 e & 22.46 \(\pm\) 6.41 a & 9.11 \(\pm\) 1.32 b & 10.09 \(\pm\) 7.06 b & 1.50 \(\pm\) 1.18 c \\
9-Decen-1-0, 1-oct-acetate & 50816-18-7 & 0.1 g & 84.30 \(\pm\) 6.87 a & 38.32 \(\pm\) 2.55 b & 17.07 \(\pm\) 12.64 c & 9.42 \(\pm\) 8.68 c \\ Decanoic acid & 334-48-5 & 0.5 e & 11.09 \(\pm\) 3.39 a & 3.89 \(\pm\) 0.57 b & 4.13 \(\pm\) 2.98 b & 0.32 \(\pm\) 0.06 c \\
1-Hexanoic acid & 142-62-1 & 0.2 e & 5.22 \(\pm\) 0.24 a & 2.05 \(\pm\) 0.49 b & 1.39 \(\pm\) 0.66 b & 0.41 \(\pm\) 0.04 c \\ Ethyl tetradacanoate & 124-06-1 & 0.5 e & 1.25 \(\pm\) 0.18 a & 0.93 \(\pm\) 0.14 b & 0.04 \(\pm\) 0.03 c & 0.03 \(\pm\) 0.03 c \\ acetic acid & 64-19-7 & 1.2 e & 0.39 \(\pm\) 0.07 bc & 0.61 \(\pm\) 0.11 a & 1.87 \(\pm\) 0.50 a & 0.16 \(\pm\) 0.12 c \\ Phenethyl alcohol & 60-12-8 & 0.045 e & 20.93 \(\pm\) 12.99 b & 55.18 \(\pm\) 8.97 b & 30.53 \(\pm\) 20.69 b & 79.29 \(\pm\) 31.91 a \\ Ethyl hexanoate & 123-66-0 & 0.005 f & 61.38 \(\pm\) 41.7 a & 52.67 \(\pm\) 8.05 b & 9.33 \(\pm\) 5.50 c & 12.59 \(\pm\) 2.81 c \\
3-Methyl-1-butanol & 123-51-3 & 0.25 e & 2.21 \(\pm\) 1.15 c & 7.05 \(\pm\) 1.36 b & 4.44 \(\pm\) 3.62 bc & 13.86 \(\pm\) 2.75 a \\
3-methylbutyl octanoate & 2035-99-6 & 0.125 f & 1.01 \(\pm\) 0.29 a & 0.56 \(\pm\) 0.17 b & 0 & 0 \\ ethyl butanoate & 105-54-4 & 0.025 f & 2.37 \(\pm\) 1.06 b & 5.43 \(\pm\) 0.82 a & 0.1 \(\pm\) 0.17 c & 0.31 \(\pm\) 0.31 c \\ (E,E)-2,4-Heptdienal & 4313-03-5 & 0.1 f & 0.87 \(\pm\) 0.34 a & 0.93 \(\pm\) 0.58 a & 1.87 \(\pm\) 1.55 a & 0.62 \(\pm\) 1.07 a \\ Hexanal & 66-25-1 & 0.005 f & 2.27 \(\pm\) 1.62 a & 1.75 \(\pm\) 0.50 a & 3.01 \(\pm\) 1.40 a & 2.31 \(\pm\) 1.07 a \\ benzoic acid & 66-85-0 & 0.5 e & 0.30 \(\pm\) 0.30 b & 0.96 \(\pm\) 0.27 a & 1.14 \(\pm\) 0.72 a & 0 \\ Acetion & 513-86-0 & 0.04 e & 3.61 \(\pm\) 0.20 b & 5.74 \(\pm\) 1.38 b & 12.12 \(\pm\) 11.74 a & 6.06 \(\pm\) 2.44 b \\ Ethyl valerate & 539-82-2 & 0.025 f & 5.17 \(\pm\) 0.61 a & 2.66 \(\pm\) 0.37 b & 3.42 \(\pm\) 1.61 ab & 3.98 \(\pm\) 1.82 ab \\ Ethyl 2-methylbutanoate & 7452-79-1 & 0.018 f & 3.22 \(\pm\) 1.18 a & 0.93 \(\pm\) 0.16 b & 0.48 \(\pm\) 0.16 b & 0.44 \(\pm\) 0.26 b \\ \hline \hline \end{tabular} Note: The significant differences (\(p<0.05\)) in the OVA values of different volatile compounds in koumiss from various regions are represented by letters a, b, c, and d. The letter e refers to the threshold value as per reference [16]. The letter f refers to the threshold value as per reference [39] with milk as the solvent. The letter g refers to the threshold value as per reference [40].  
\end{table} 
Table 3: OVA content of volatile substances in koumiss from different regions. YL region, which may be a manifestation of excessively high levels of Octanoic acid and n-decanoic acid. For the milky attribute, the ALTw region had the highest score, with an intensity of 4.2. The ALTe region had the highest score for the floral attribute, which was related to the content of phenylethanol. Interestingly, the sensory profile characteristics of kouniss in different regions are quite different. These phenomena indicate that the metabolic capacity of flavor substances produced in the fermentation process of kouniss differs due to different fermentation conditions and other factors, which provides a theoretical basis for establishing and differentiating kouniss fermentation techniques with specific sensory characteristics.