## 3 Results and Discussion
### Volatile Composition of Fermented Beverages and Its Relationship with Their Sensory Properties  
Significant differences were detected among the fermented beverages' flavors, as shown in Table 3. RATA results showed that the main differences among samples were due to the beverage type, with the rice beverage and its derivatives exhibiting more cereal, legume, nutty-like, and watery characteristics than the dairy products. The rice beverage used in the present study was mainly characterized by being sweet, watery, and having cereal aroma notes. Similar flavors were reported in a previous study in which up to 90 different plant-based beverages had been characterized using a RATA sensory test and GC-MS-olfactometry [14]. In general, plant-based beverages have been reported to have different kinds of off-flavors, such as beauty and painty aromas or a chalky mouthfeel [36]. However, the sensory profile is quite variable, even within a specific product category [14]. Results of the present research confirmed the presence of some legume and nutty aromas in the rice beverage, also extending to the fermented samples, suggesting that the fermentation process did not diminish the intensity of these flavor notes. Although previous research reported some non-desirable flavors, such as hay-like or astringency, in different rice beverage brands, the sample used in the present study was not characterized by these additional notes. The quality guidelines for USDA specifications report that the flavor profile of yogurt should be \"acid, free from undesirable flavors such as bitter, rancid, oxidized, stale, yeasty and unclean\" [20]. In this study, fermentation reduced sweetness and wateriness and increased sourness, cheese-like, and thickness in dairy milk, but it had no such effect on the rice beverage. Although some flavor trends could be observed in the rice beverages results, the only significant difference was that the fermented LLV beverage had a higher sourness than the original beverage. In general, no significant differences were found between beverages derived from the same raw material but fermented using different bacteria strains. Volatile composition results also suggested that the main differences among samples were due to the beverage type. However, fermentation had a significant role in altering the composition of both dairy milk and rice beverage samples. Table 4 shows the volatile compounds, grouped by chemical families, found in the different samples. Dairy milk and its fermented samples were characterized by having a volatile profile in which different ketones, acids, esters, hydrocarbons, and lactones were present. However, the concentration of total acids (e.g., cheese, fatty, sour) significantly increased during fermentation. These results, as well as the sensory data, corresponded with the volatile composition previously found in milk and yogurt, characterized by the presence of \(\delta\)-decalactone and different organic acids, among others [37; 38]. The concentration of specific volatile compounds such as dimethyl sulfone, octanoic and decanoic acid ethyl esters (apricot, floral, grape, oily, pear), \(\delta\)-decalactone (musty, fatty, fruity), or limonene (lemon, orange, citrus, sweet) significantly increased in the LLV fermented sample, suggesting a deeper transformation of the raw material due to the microbial activity of this bacterial combination. On the other hand, some ketones, such as 2-nonanone, increased in the CH dairy milk fermented sample, providing cheese, coconut, or oily aromas to this beverage. Rice beverage was characterized by a high concentration of aldehydes (e.g., fatty, green, oily, fruity, apple), confirming a previous study in which this chemical family was reported as being predominant in different commercial rice beverages [14]. Fermentation was able to significantly reduce the concentration of aldehydes, ketones, and alcohols in this matrix, as well as increasing the acid content. In general, total volatile compounds increased during fermentation in the dairy milk sample.