# Shedding Light on the Volatile Composition of _Broa_, a Traditional Portuguese Maize Bread
## 3 Results and Discussion
### Characterization of the Volatile Composition of Broas
#### 3.4.3 _Broas_' Sensory Analysis and Volatile Composition
Similarly, B1 belonged to cluster 3, together with B2, B5, B9 and B10, characterized by higher amounts in lipid oxidation products, such as hexanal and heptanal, which were negatively correlated with 'taste and aroma' scores. B11, followed by B3, showed the highest 'taste and aroma' scores. These samples and B4, which showed the fourth highest scores, all belonged to cluster 2 (Figure 5 and Table 4), characterized by lower contents in volatiles from lipid oxidation reactions, in particular octanal, which has a low odor threshold and is considered an off-flavor of foods [17; 24]. Indeed, a significant negative correlation was found between 'taste and aroma' scores and octanal. This cluster was also characterized by lower contents of 3-ethyl-2-methyl-1,3-hexadiene and benzaldehyde, which also showed negative correlations with 'taste and aroma' scores, along with other aldehydes derived from lipid oxidation reactions, namely 2-nonenal (_E_) and 2-undecenal, frequently described as negative contributors to the aroma of breads [20]. These results explain some differences among _broas_ prepared from the traditional and commercial hybrid maize varieties and sustain the previous knowledge of producers regarding the better-quality aspects of traditional maize varieties for _broas_' production [4]. In particular, according to the producers, the _broa_ of traditional maize is softer, sweeter and can be preserved for longer periods than _broas_ produced with hybrid varieties [81]. Indeed, higher contents in pyranones may contribute to traditional _broas_ sweeter taste, and lower contents in aldehydes suggest that lower lipid oxidation reactions were occurring in traditional samples, which can not only explain their longer preservation, but also contribute to their more pleasant flavor. Positive correlations were found between'smell and odor' scores and 2,3-dihydromekorfuran, which was more abundant in _broas_ with higher carotenoids' content, as previously discussed. To the best of our knowledge, 2,3-dihydrobenzofuran has not been described neither in other maize-based foods nor cereal breads and was not detected in maize flours, so it was originated during the bread making process, similar to other furan derivatives [14; 15; 16]. This compound has been described in wines and soy sauce as a product of the Maillard reaction [82; 83] and is associated with musky notes [55]. Very strong and positive correlations were found between the main products of carotenoids' degradation (\(\alpha\)-ionone and geranylacetone) and color scores, which can be explained by the preference for _broas_' yellowish color by the panel of consumers. The 'global appreciation' of _broas_ was greatly influenced not only by 'flavor and aroma', but also by 'texture', which also showed a very strong positive correlation between them (Supplementary Table S11). _Broas_ with higher contents in some volatiles associated with off-aromas, such as octanal, 2-octenal and 2-nonenal, also showed lower scores for texture, whereas samples with higher pyranones content showed higher scores. These findings may be explained by the proteolysis reactions that occur during sourdough fermentation [9; 84]. Briefly, proteolysis produces amino acids and other precursors of aroma compounds during baking, enhancing the formation of volatiles related to better bread flavor [9], while simultaneously improving the dough rheology and bread texture, resulting in a large reduction of elasticity and firmness of the dough [84]. Most of the volatiles commonly described as great contributors for other cereal breads and maize-based foods, such as 2-acetylpyrroline, 2-(methylimino)-3-butanone and 2,3-butanedione [8; 85], were not detected in _proas_. Therefore, their absence can account for the different sensory characteristics of _proas_[81], when comparing to other cereal breads. In particular, 2-acetyl-1-pyrroline, a compound derived from the Maillard reaction, has been referred to as the main compound responsible for the characteristic flavor of wheat bread crust [24; 26; 36].