## 3 Results and Discussion
### Evolution of VOC Profiles During Successive Kefir Grain Passages

Table 4: Older activity values (OAVs) of the volatile organic compounds detected in the different kirai-like beverages obtained from the third keir grain passage (48–72 h). \begin{table}
\begin{tabular}{l l c c c c c c c c c} \hline
**No.** & **Compound** & **Dev1-72 h** & **Dev2-72 h** & **Dev3-72 h** & **Dev4-72 h** & **Dev5-72 h** & **Dev6-72 h** & **Dev7-72 h** & **Dev8-72 h** & **Dev9-72 h** \\ \hline
21 & Benzaldehyde & 0.81 & 0.32 & 0.41 & 0.49 & – & 0.56 & 0.71 & – & 0.57 \\ \hline
22 & Furural & 0.01 & – & – & – & – & – & – & – & 0.07 & – \\ \hline \multicolumn{11}{c}{} & \multicolumn{8}{c}{Ketones} \\ \hline
23 & 2.6-Dimethyl-4-heptanone & _7.73_ & _7.91_ & _9.36_ & _12.36_ & _11.64_ & _12.09_ & _6.73_ & _2.55_ & _12.82_ \\ \hline
24 & 2-Heptanone & – & – & – & – & – & – & – & – & – \\ \hline
25 & 4-Methyl-2-hexanone & – & – & – & – & – & – & – & – & – \\ \hline \multicolumn{11}{c}{} & \multicolumn{8}{c}{Esters} \\ \hline
26 & 2-Methylbutyl acetate & 2.81 & – & – & – & – & – & 3.56 & – & – \\ \hline
27 & 2-Phenylethyl acetate & 0.96 & 0.52 & 0.68 & – & 0.56 & 0.76 & 0.76 & – & – \\ \hline
28 & Ethly 3-phenyl/propanoate & 10.71 & – & – & – & – & – & – & – \\ \hline
29 & Ethly butanoate & – & – & – & – & – & – & – & 211.11 \\ \hline
30 & Ethly decanoate & – & – & 4.10 & 3.45 & – & 2.75 & 2.45 & – & 2.65 \\ \hline
31 & Ethly dodecanoate & – & – & 0.06 & 0.06 & – & 0.06 & 0.05 & – & 0.03 \\ \hline
32 & Ethly hexadecanoate & – & – & 0.19 & 0.15 & – & – & – & – & – \\ \hline
33 & Ethly hexanoate & 74.29 & 125.00 & 32.86 & 16.43 & – & – & 10.00 & – & – \\ \hline
34 & Ethly octanoate & 84.00 & 20.00 & 84.00 & 106.00 & – & 86.00 & 56.00 & – & 140.00 \\ \hline
35 & Heayl acetate & – & – & 0.19 & – & – & – & – & – & – \\ \hline
36 & Methyl benzoate & 461.54 & – & 557.69 & – & – & – & 269.23 & – & 384.62 \\ \hline
37 & Pentyl acetate & – & 1.16 & 11.40 & – & 7.44 & 10.00 & – & – & – \\ \hline \multicolumn{11}{c}{} & \multicolumn{8}{c}{Furans} \\ \hline
38 & 2.5-Dimethyl-4-hydroxy-3(2H)- & 24.00 & 21.00 & 38.00 & _37.00_ & – & 29.00 & 30.00 & 31.00 & 40.00 \\ \hline \multicolumn{11}{c}{} & \multicolumn{8}{c}{**Number of VOCs with OAVs \(\geq\) 1.0**} \\ \hline \end{tabular}
\end{table} 
Table 4. _Cont._The volatile compounds with OAVs > 1.0 identified in these six beverages included 1-pentanol (present in all six beverages), 1-hexanol (Bev7-24 h and Bev2-48 h), 2-phenylethanol (Bev7-24 h Bev2-48 h, and Bev8-48 h), 2-undecanol (Bev7-48 h and Bev8-48 h), (E)-2-nonenal (Bev7-24 h and Bev8-48 h), and 4-hydroxy-3-methoxybenzaldehyde (vanillin) (all six). Other compounds included 2,6-dimethyl-4-heptanone (all six), pentyl acetate (Bev7-24 h), methyl benzoate (Bev1-24 h, Bev7-24 h, Bev2-48 h, and Bev8-48 h), ethyl octanoate (Bev1-24 h, Bev2-24 h, Bev2-48 h, and Bev7-48 h), ethyl decanoate (Bev7-48 h), ethyl hexanoate (Bev1-24 h and Bev7-48 h), and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (all six). As a result, these beverages are characterized by fruity, sweet, floral, rose-like, creamy vanilla-like, and caramel-like aromas. However, additional unpleasant resinous notes were detected in Bev7-24 h and Bev2-48 h, while fatty notes were present in Bev7-24 h and Bev8-48 h. Furthermore, all six beverages exhibited pungent, fermented, bready, yeasty, fused, oily, winey, and solvent-like odor descriptors. In contrast, Bev8-72 h, Bev3-72 h, Bev7-72 h, Bev3-24 h, Bev4-72 h, Bev1-72 h, Bev8-24 h, and Bev9-72 h were the most distinct beverages (Figure 4), each containing 7, 14, 13, 10, 14, 11, 7, and 17 volatile compounds, respectively, with OAVs considerably greater than 1.0 (Tables 2-4).