## 3 Results and Discussion
### Evolution of VOC Profiles During Successive Kefir Grain Passages
The volatile compounds detected in these beverages included 1-pentanol (present in all eight beverages), 2-methyl-1-propanol (Bev1-72 h and Bev9-72 h), 3-methyl-1-pentanol (Bev3-24 h and Bev7-72 h), 1-dodecanol (Bev3-24 h, Bev3-72 h, Bev4-72 h, and Bev9-72 h), 1-hexanol (Bev4-72 h and Bev9-72 h), 1-octanol (Bev9-72 h), 2-phenylethanol (Bev1-72 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, Bev8-72 h, and Bev9-72 h), 2-heptanol (Bev9-72 h), 2-undecanol (Bev8-24 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, Bev8-72 h, and Bev9-72 h), (E)-2-hexneal (Bev4-72 h and Bev9-72 h), (E)-2-nonenal (Bev3-72 h, Bev4-72 h, Bev7-72 h, Bev8-72 h, and Bev9-72 h), 2-methylbutanal (Bev8-24 h and Bev8-72 h), 4-hydroxy-3-methoxybenzaldehyde (Bev3-24 h, Bev8-24 h, Bev1-72 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, and Bev9-72 h), 2,6-dimethyl-4-heptanone (present in all eight beverages), 2-heptanone (Bev3-24 h), 4-methyl-2-hexanone (Bev8-24 h), 2-methylbutyl acetate (Bev1-72 h and Bev7-72 h), pentyl acetate (Bev3-72 h), ethyl 3-phenylpropanoate (Bev1-72 h), ethyl butanoate (Bev9-72 h), methyl benzoate (Bev3-24 h, Bev1-72 h, Bev3-72 h, Bev7-72 h, and Bev9-72 h), ethyl decanoate (Bev3-72 h, Bev4-72 h, Bev7-72 h, and Bev9-72 h), ethyl hexanoate (Bev3-24 h, Bev1-72 h, Bev3-72 h, Bev4-72 h, and Bev7-72 h), ethyl octanoate (Bev3-24 h, Bev1-72 h, Bev3-72 h, Bev4-72 h, and Bev7-72 h), ethyl octanoate (Bev3-24 h, Bev4-7(Bev3-24 h, Bev1-72 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, and Bev9-72 h), and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (present in all eight beverages). Thus, the broader aromatic profile of these beverages includes fruits, sweet, and caramel-like notes. In addition, several pleasant aromas were identified, such as malt (Bev1-72 h and Bev9-72 h), wine-like (Bev3-24 h and Bev7-72 h), raw carrot (Bev3-24 h, Bev3-72 h, Bev4-72 h, and Bev9-72 h), soapy (Bev9-72 h), honey (Bev1-72 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, Bev8-72 h, and Bev9-72 h), nutty (Bev8-24 h and Bev8-72 h), and creamy vanilla-like (Bev3-24 h, Bev8-24 h, Bev1-72 h, Bev3-72 h, Bev4-72 h, Bev7-72 h, and Bev9-72 h). However, pungent, fermented, bready, yeasts, fusel, oily, winey, and solvent-like odors were also present across all eight beverages. Some samples exhibited unpleasant notes, including resinous (Bev4-72 h and Bev9-72 h), bitter almond-like (Bev4-72 h and Bev9-72 h), and fatty odors (Bev3-72 h, Bev4-72 h, Bev7-72 h, Bev8-72 h, and Bev9-72 h). Additionally, the beverages Bev5-24 h and Bev5-48 h exhibited the poorest aromatic profiles, with only four volatile compounds having an OAV greater than 1.0. These findings confirm that variations in the shaking rate and inoculum proportion can significantly influence the volatile composition, resulting in kefir-like beverages with unique aromatic profiles and distinct sensory characteristics. Relationships Among the Microbiological, Chemical, and Volatile Odorant Compositions of Beverages from the Three Kefir Grain Passages  
To complete the present study, a third PCA was conducted based on the microbiological and chemical compositions [11] and the number of volatile compounds with OAVs greater than 1.0 (Tables 2-4) in the 28 kiwifruit-based beverages. This analysis included the counts of LAB, AAB, and yeasts, as well as the concentrations of citric acid, quinic acid, lactic acid, acetic acid, ethanol, glycerol, and total sugars [11]. Using this approach, the initial 11 independent variables were reduced to three principal components (PC1, PC2, and PC3) with eigenvalues greater than 1.0 (Table S27). These components accounted for 36.31%, 29.90%, and 16.00% of the variance, respectively. Together, the three components explained 82.21% of the total variance (Figure 5A, Table S27). The first principal component (PC1) was positively correlated, in descending order, with the AAB count, lactic acid concentration, and yeast count, and negatively correlated with the citric and quinic acid levels.