# Volatile Organic Compounds in Breads Prepared with Different Sourdoughs
## 3 Results
### Volatile Organic Compounds of Bread
[42] showed that hexanol was produced more by heteroferrattative than homoferrattative bacteria in the dough. Pentanol ranged between 6.17 ng/g in S2 and 14.48 ng/g in S3. [PERSON] et al. [48] showed a range of concentrations of 19.6 to 24 ng/g in bread crumb depending on temperature fermentation and the quantity of yeast added to prepare the bread, while [PERSON] et al. [43] showed a range of concentrations between 78 and 129 ng/g depending on the commercial bakery yeast used. This compound influences the odors of oil, sweet, balsamine, and chemical mint, and the perception threshold in water is 4000 ppb, a very high concentration [3,49]. It originates both by fermentative reactions and lipid oxidation [3,48], and it is present in the crust and crumb of bread [50]. Finally, the 2-ethyl-1-hexanol concentration ranged between 4.73 in S2 and 5.81 ng/g in S4, and the concentration ranged between 4.52 ng/g and 8.89 ng/g in bread crumb depending on the yeast quantity and temperature of fermentation [48] or between 9 and 27 ng/g depending on the commercial bakery yeast used [43]. This compound influences the odor of green/vegetables [11,47,51], and it was found in the crust and crumb bread [50]  
The aldehydes ranged between 185.01 ng/g (33.29% of total VOCs) in S2 and 454.95 ng/g (42.38% of total VOCs) in S4. The identified aldehydes were 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, hexanal, 3-furfural, heptanal, benzaldehyde, octanal, benzenactaldehyde, and nonanal. 2-Methylpropanal ranged between 2.33 in S3 and 12.78 ng/g in S4, while the 3-methylbutanal concentration ranged between 23.24 in S1 and 110.69 ng/g in S4. [PERSON] et al. [43] showed a concentration that ranged between 11 and 47 ng/g in the crumb of bread prepared with different types of commercial yeasts, while [PERSON] et al. [48] showed a concentration that ranged between 5 and 10.8 ng/g, a concentration that depends on the fermentation temperature of the dough. The 2-methylbutanal concentration ranged between 9.13 in S2 and 29.37 ng/g in S4. [PERSON] et al. [52] showed a concentration that ranged between 1 and 5 ng/g, and this compound was found in the crumb and crust [53]. 2-Methylpropanal, 2-methylbutanal and 3-methylbutanal are Strecker aldehydes derived by amino acid conversion by yeast; in particular, 2-methylpropanal derives from valine, 2-methylbutanal from isoleucine, and 3-methylbutanal from leucin. These aldehydes are characterized by a malty and fruity odor with a very low odor threshold in water that ranges between 0.1 and 2.3 ppb [3,49,52]. The concentration of hexanal ranged between 59.59 ng/g in S2 and 103.69 ng/g in S4. A previous report indicated a concentration that ranged between 222 ng/g and 393 ng/g in the crumb of bread prepared with different commercial yeasts or 11.8 ng/g to 20.1 ng/g in bread prepared with different quantities of _Saccharomyces cerevisiae_ and at different fermentation temperatures [43,48], while [PERSON] et al. [52] showed a concentration that ranged between 13 ng/g and 26 ng/g depending on the storage time of bread. This compound is present in the crust and crumb [50,53], and it influences fresh, green, fatty, aldehyde, grass, leafy, fruity, and sweaty odors [3,11,49], with a measured odor threshold in water of 4.5-5 ppb [3,47,48]. This aldehyde is derived from lipid oxidation [44,48,52]and the fermentative metabolism of microbes [48]. Lipid oxidation compounds are often characterized as being off-flavor; therefore, the high level of hexanal in fermented bread might result in a lower acceptance of bread [48]. Furthermore, its presence in sourdough and bread was reported [3; 52]. The furfural concentration ranged between 16.73 ng/g in S2 and 94.66 ng/g in S4. [PERSON] et al. [41] showed a concentration that ranged between 20 and 190 ng/g depending on the concentration and composition of sourdough used to prepare the bread. This molecule gives burnt, sweet, woody, almond, bread, and rancid odors to bread, and its odor threshold in water is approximately 3000-23,000 ppb [3; 48].