# Volatile Organic Compounds in Breads Prepared with Different Sourdoughs
## 3 Results
### Volatile Organic Compounds of Bread  
In Table 5, the volatile organic compounds (VOCs) of bread prepared with different sourdoughs are shown. Alcohol, aldehydes, and acetic acid were the prevalent VOCs (>100 mg/g) found in all samples. The total alcohol concentration ranged between 140.88 ng/g in S2 (25.34% of VOCs) and 401.20 ng/g (37.32% of VOCs) in S3. The alcohols present in bread were ethanol, 3-methyl-1-butanol, 2-methyl-1-butanol, 1-pentanol, 1-hexanol, 2-phenylethanol, and 2-ethyl-1-hexanol. The ethanol concentration ranged between 58.45 ng/g in S2 and 202.73 ng/g in S1, and alcohol was present at the highest concentration in all types of bread. [PERSON] et al. [41] showed a concentration that ranged between 140 ng/g and 4970 ng/g, depending on the day of bread storage. This compound is derived from the metabolism of _Saccharomyces cerevisiae_, which is able to transform fermentable glucides in ethanol that evaporates during baking. The remaining part of ethanol can participate in secondary fermentation reactions, such as glycolysis of pyruvate acid, which leads to short-chain alcohols, short-chain fatty acids, esters, and carbonyl compounds [11]. [PERSON] et al. [12] showed that the ethanol content increased in sourdoughs supplemented with yeast. Ethanol is produced by LAB at a higher rate by heteroferrattative species than homoferrattative species in rye sourdoughs [42], and ethanol influences bread flavor with an odor described as strong, alcoholic, ethereal, and medicinal with a perception threshold in water of 100,000 ppb [3]. The concentration of 3-methyl-1-butanol ranged between 30.24 ng/g in S2 and 97.46 ng/g in S3, a concentration lower than that reported by [PERSON] et al. [43] at 6313 ng/g and 8768 ng/g depending on the commercial baker's yeast used to prepare bread. This compound is characterized by an odor described as banana, fruity, and almonds, and its odor threshold ranges between 250 and 300 ppb in water [3]. Its concentration increases in sourdoughs supplemented with yeasts [8]. The concentration of 2-methyl-1-butanol ranged between 3.43 ng/g in S2 and 13.30 ng/g in S3, and the amounts of 2- and 3-methyl-1-butanol increased in sourdoughs with added yeast [8]. The formation of 3-methyl-1-butanol and 2-methyl-1-butanol could be derived during fermentation from flour amino acids (leucine and isoleucine, respectively) via the Ehrlich pathway in yeast cells [44]. The concentration of 2-phenylethanol ranged between 4.26 ng/g in S2 and 18.96 ng/g in S3, while [PERSON] et al. [43] showed a concentration that ranged between 32 and 178 ng/g in breads prepared with different types of commercial yeasts. This compound gives the odor of flowers and rose [45], but the perception threshold in water was in the range of 750 to 1100 ppb [3]. Furthermore, it was reported that it was positively correlated with the flavor of wheat crumb [46], and it could be derived from the fermentation of phenylalanine via the Ehrlich pathway in yeast cells [44]. Prolonged dough fermentation and the presence of _Saccharomyces cerevisiae_ increase the concentration of 2-phenylethylanol [47]. The concentration of hexanol ranged between 33.60 in S2 and 65.72 ng/g in S3. [PERSON] et al. [48] showed a concentration that ranged between 42.5 ng/g and 53.4 ng/g in wheat bread crumb depending on the quantity of yeast added and fermentation temperature, while [PERSON] et al. [43] showed a range between 360 and 589 ng/g depending on the commercial bakery yeast used. Apart from ethanol, 1-hexanol was the dominant alcohol in all sourdough breads. [PERSON] and [PERSON] [8] showed that this compound was present in sourdough prepared both with starter cultures and starter cultures and sourdough yeasts. This compound influences the odors of ethereal, oil, alcohol, green, fruity, sweet, woody, and floral compounds. It originates from fermentative reactions and/or lipid oxidation, and its odor perception threshold in water is in the range of 2500 ppb [3,48]. Furthermore, [PERSON] et al.