# Bread Biopreservation through the Addition of Lactic Acid Bacteria in Sourdough
## 3 Results and Discussion
### Analysis of Volatile Organic Compounds  
The VOC profile varies mainly due to compounds produced during fermentation, enzymatic reactions, lipid oxidation, and thermal shock, according to [PERSON] et al. [38]. The three main pathways for VOC formation are fermentation, in which mainly acids, alcohols, esters, and ketones are produced; lipid oxidation, in which mainly ketones and aldehydes are produced; and the Maillard reaction, which gives rise to pyrazines, pyridines, and pyrroles [39]. These compounds are widely studied in sourdough breads to find new possibilities to improve odor and flavor [38]. A total of 56 compounds were identified in this study and all volatile compounds are described in Table S1. A total of 42 VOCs were identified in the doughs at T0 (Figure 3a), including acids (2), alcohols (8), aldehydes (15), alkanes (3), esters (5), ketones (7), and terpenes (2). At a general level, the major compounds were alcohols and aldehydes. The relative percentage of alcohols varied between 22% and 50.8% of the total compounds detected, depending on the sample. In addition, there was a higher concentration in SB1 and SB2. It is remarkable that the presence of 1-butanol and 3-methyl exists in all the samples except in SBC. The relative percent area of all volatile compounds identified at T0 is described in Table S2. This compound is produced in the metabolism of leucine and phenylalanine by yeasts, according to [PERSON] et al. [38]. In addition, a significant presence of 1-octen-3-ol was also observed in SB1 and SB2. These two compounds were also detected in sourdough fermented by _L. plantarum_ PON100274 for 8 h [40]. In addition, as [PERSON] et al. [41] demonstrated, 1-butanol is described as a compound that positively influences the aroma, while 3-methyl has a negative impact. Figure 3: _Cont._  
Regarding aldehydes, they varied between 24.6% and 39% of the total number of compounds identified. These compounds begin to be produced during kneading, when the fatty acids in the flour bind with oxygen, according to [PERSON] et al. [38]. It is worth noting the presence of hexanal in SB\({}_{1}\), that of 2-nonenal in dough control, and that of decanal in SBC. In [PERSON] et al. [42], the presence of hexanal was also observed in the sourdough fermented by _L. plantarum_. These compounds are the majority in wheat flour [41]. On the other hand, a considerable presence of terpenes was also seen, varying between 12% and 22.6% depending on the dough. The presence of d-limonene in SBC and the presence of linalool in SBC, SBC\({}_{\text{p}}\), and SB\({}_{2}\) is also noteworthy. Regarding acids, they were only detected in SBC\({}_{\text{p}}\), and both the amount of propionic acid and hexanoic acid was considerable, a consequence of the addition of propionate. In the doughs after fermentation (Figure 3b), a total of 49 VOCs were identified, among which were acids (1), alcohols (9), aldehydes (16), alkanes (1), esters (15), ketones (5), and terpenes (2). In general, the major compounds were alcohols, aldehydes, and esters. The latter increased during fermentation, due to lipid metabolism and yeast growth, according to [PERSON] and [PERSON] [43]. In addition, there was also an increase in the percentage of  
Figure 3: The relative percentage of volatile organic compounds. (**a**): doughs at T0; (**b**): fermented doughs; (**c**): baked breads. BC: bread control; SBC: sourdough bread control; SBC\({}_{\text{P}}\): sourdough bread control with propionate; SB\({}_{1}\): sourdough bread with _L. plantarum_ 5L1 inoculum (0.5%); SB\({}_{2}\): sourdough bread with _L. plantarum_ 5L1 inoculum (5%). Different lower-case letters indicate a significant difference in compound concentrations between treatments (\(p\geq 0.05\)). ketones in SB\({}_{2}\), an overall decrease in the concentration of terpenes, and a reduction in acids in SBC\({}_{\text{P}}\). The relative percentage of alcohols with respect to the rest of the compounds varied between 15.54% and 36.15%, being the highest in dough control.