# Shedding Light on the Volatile Composition of _Broa_, a Traditional Portuguese Maize Bread
## 3 Results and Discussion
### Characterization of the Volatile Composition of Maize Flows
Thus, the different granulocyte of the commercial flour was probably not the main reason for its higher content in aldehydes and alcohols. Ultimately, the lower content of lipid oxidation derivatives in the traditional maize flours may also be caused by their higher amounts in antioxidant compounds [11]. Consequently, the total carotenoids content and major soluble phenolic compounds present in maize flours (ferulic and \(p\)-coumaric acids, diferuloyl putrescine, coumaroyl feruloyl putrescine, dicoumaroyl spermidine and _bis_-diferuloyl putrescine) were quantitated (Supplementary Table S3) and correlated to their volatile composition (Supplementary Table S4). Results showed strong negative correlations among several volatile compounds derived from lipid oxidation [15; 17], namely 1-hexanol, 2-pentylfuran, 1-octanol, 1-nonanol, 2-undecenal and pentadecane, and some phenolic compounds, such as ferulic acid, diferuloyl putrescine, coumaroyl feruloyl putrescine and _bis_-diferuloyl putrescine, whereas no positive correlations were found. Similarly, pantolactone, also possibly derived from lipid oxidation reactions [15], showed very strong and negative correlations (R < -0.70, \(p\) < 0.01) not only with diferuloyl putrescine, but also with total carotenoids' content. Hence, phenolic compounds in traditional maize flours and, to a lesser extent, carotenoids, may have inhibited lipid oxidation reactions, and contributed to their longer preservation. In fact, ferulic acid has been approved in certain countries as a food additive to prevent lipid oxidation [69]. As the differences between the traditional and commercial maize flours were high, it was not possible to detect any dissimilarities among the traditional maize varieties. Thus, a second analysis was performed, excluding the commercial sample and benzaldehyde, once it was not detected in the traditional maize varieties. The analysis was performed considering the first 5 components obtained by the PCA, which explained 91.3% of the total variance. The optimal number of clusters obtained by the elbow point and silhouette methods now corresponded to 3 clusters. The resulting dendrogram is presented in Figure 3 and the compounds that significantly contributed to discriminate the clusters are presented in Table 3. Samples from cluster 1 (F3, F5, F6, F9 and F11) were distinguished from cluster 2 (F2, F4, F7, F8, F10) by their lower contents in ketones (\(\alpha\)-ionone, 6-methyl-5-hepten-2-one and geranylacetone), derived from carotenoids' oxidation [40; 59] and higher pontolactone contents (Supplementary Figure S3). Geranylacetone, \(\alpha\)-ionone and 6-methyl-5-hepten-2-one showed strong and positive correlations among them (R > 0.7, \(p\) < 0.05) (Supplementary Table S2). Therefore, a higher content of carotenoids and/or higher carotenoids' oxidation reactions led to an increase in these compounds. Indeed, strong and positive correlations were found between total carotenoids' content and both \(\alpha\)-ionone and geranylacetone (Supplementary Table S4). In addition, all the samples from cluster 2 were yellow kernels, showing higher total carotenoids' content (Supplementary Table S3), corroborating the results from a previous study [40]. The concentrations in geranylacetone and \(\alpha\)-ionone can also be influenced by the expression of genes encoding carotenoid cleavage dioxygenases [60; 61]. Ultimately, higher amounts in compounds that inhibit carotenoids' oxidation, such as ferulic and \(p\)-coumaric acid or other phenolic derivatives, can also contribute to lower concentrations in these compounds. In fact, moderate negative correlations were found between geranylacetone and \(p\)-coumaric acid and between 6-methyl-5-hepten-2-one and ferulic acid (Supplementary Table S4). Figure 2: Representative scheme of lipid oxidation reactions [15; 17; 20; 28; 35] occurring in maize flour samples.