## 3 Results
### Carbohydrates and Acids in Fermented Samples
#### 3.5.2 Characteristic VOCs of Soy, Oat and coconut  
A total of 54-untargeted volatile compounds were identified by GC-MS in all three fermented bases. They comprised ketones, esters, acids, aldehydes, alcohol, furans, sulfurs, lactones, terpen, benzenes, and aromatic compounds. 12 of them (ethyl acetate, 2,3-pentanedione, hexanal, ethyl decanoate, \(\alpha\)-pinene, benzaldehyde, 3-carene, acetoin, \(\delta\)-decalactone, \(\gamma\)-octalactone, dimethyl disulfide, and 2-heptanone) were present in the three fermented bases. Some compounds, such as acetone and diacetyl, were identified by FID and also detected by GC-MS, two methods based on different detection principles. Previous studies were taken as references for predominant volatiles of soy [98; 104; 105], oat [40; 101], and coconut [106; 107]. The identification of compounds in this study was compared to their results. Two compounds were present in all three fermented samples, namely hexanal and benzaldehyde. Hexanal is mainly produced through linoleic acid oxidation and it can be further oxidized to hexanoic acid and reduced to 1-hexanol by dehydrogenase enzymes during fermentation processes [101]. Since linoleic acid is the primary fatty acid in oat [101] and soybeans [92], detection of hexanal in fermented soy and oat samples was expected in this study. Hexanal content was significantly higher in these two fermented bases in comparison to fermented coconut samples, where it was found in very low quantities, as previous studies suggested [107]. No significant effect of the different culture combinations was found in any of the bases, which indicates that LGG(r) did not have any effect on its production. [PERSON] et al. detected its presence in soy milk and in soy blends and observed changes in its levels during storage, attributing them to further lipid oxidation [104]. Hexanal is associated with green and beany odors [105], but also related to rancidity [41]. Nevertheless, [PERSON] et al. stated that, since hexanal is present in oat samples with acceptable flavors, perception of rancidity is not directly linked to the presence of hexanal but to its concentration [108]. Regarding benzaldehyde, a compound found in Camembert cheese [109], it was significantly higher in fermented oat samples, followed by coconut and soy samples. [PERSON] et al. and [PERSON] et al. reported its presence in soy milk products and in germinated soy, but stated its minor contribution to soybean aroma [104; 105]. [PERSON] [100], [PERSON] [40], and [PERSON] [101] detected the presence of benzaldehyde in uncooked and cooked oatmeal and attributed it to an almond odor. Its presence could be associated with reducing sugars and amino acids interactions [108]. [PERSON] et al. identified benzaldehyde in coconut milk [110], and fermented coconut samples in this study were the only ones showing significantly different benzaldehyde content between the different culture combinations (Table 12). However, LGG(r) had no significant effect on benzaldehyde production. The main contributors to soy flavor (in addition to hexanal and benzaldehyde) are nonanal, heptanal, octanal, acetic acid, 1-hexanol, 1-pentanol, 1-octen-3-ol, heptanol, 2-pentyl, furan, 2-ethyl furan, 1-octen-3-one [98; 104; 105]. From this list, only hexanal and benzaldehyde were identified in fermented soy samples in this study, and none of the different culture combinations had an effect on their quantity. Nevertheless, other volatile compounds were found in fermented soy samples, and those whose production was affected by LGG(r) are shown in Table 13, 2-heptanone is a product of octanoic acid metabolism and it was detected in low amounts in fermented soy samples, which is aligned with the results from [PERSON] et al. [111]. They found this compound in soy cheese and also in Cheddar cheese. [PERSON] et al. associated it with milk off-flavor [112], but literature highlights its main role in blue cheeses [113].