## 2 Results and Discussion
### Exploring the Volatile Compounds Associated with Baking
#### 2.2.6 Sulfur-Containing Compounds  
Sulfur compounds had not been previously reported in broas [27], possibly due to their low concentrations. Usually, foods from cereals show very low contents in sulfur-containing compounds due to the low amounts of sulfur amino acids [20]. However, sulfur-containing Maillard odorants constitute the most powerful aroma compounds of foods, even though they are present at trace levels [14; 15]. These compounds have traditionally been associated with unpleasant and noxious off-flavors [13; 14]. Still, they contribute to positive flavor characteristics at low concentrations (<1 ug kg\({}^{-1}\)), giving tropical, fruity, and savory aromas to foods [13]. They are considered \"character-impact compounds\" of bread crust, popcorn and toasted cereal grains [13; 15].  
Dimethyl sulfide (S2), dimethyl disulfide (S3), and, in particular, dimethyl trisulfide (S8) may be extremely relevant for the aroma of _broas_. At low levels, they all show positive aroma characteristics. Dimethyl trisulfide (S8) has an extremely low OT of 0.01 ug L\({}^{-1}\)[43] and, when present at low concentrations, is associated with tropical fruit and grapreruit aromas [13]. The most abundant sulfur compound detected _in broas_ was dimethyl disulfide (S3), an important contributor to maize flavor [24]. Dimethyl sulfide (S2) is considered a flavor impact compound of sweet maize and conveys the typical flavor impression of canned maize when present at reduced levels [13]. Methanethiol (S1) was the second most abundant sulfur-containing compound and may also significantly impact the aroma of _broas_. It has been described as a possible contributor to the aroma of sweet maize [13].  
Another sulfur-containing compound detected in _broas_ was the very well-known methtional (S7) [68], possibly also one of the most relevant volatiles for the aroma of _broas_. It is a potent [5] and desired odorant [21], with a characteristic potato-like aroma [7; 59]. It has been considered a key odorant of fried foods [43], wheat, rye [7] and Chinese white [49] bread. It may be responsible in part for typical popcorn [33], maize tortilla chips [43] and taco shell [32] aroma characteristics. Furthermore, it has flavor-modifying characteristics since it has been shown to suppress flavor and aroma [59]. Other aliphatic sulfur compounds detected in _broas_ were 1-methylthiophene (S4) and methylthio-2-propanone (S5). These compounds have not been described in similar foods, and their impact on the overall aroma of _broas_ is unknown.  
Regarding aromatic sulfur heterocycles derivatives, it was possible to detect three thiazoles and six thiophenes. Thiazoles usually confer green, vegetable-like, cocoa and nutty aromas to foods [20], while thiophenes contribute to sulfurous, nutty and fatty aromas [51]. Among them, 2-acetylthiazolc (Tz2) may have high importance in the aroma of _broas_. It has been described as a key volatile of popcorn and maize flour extrudates [40].  
It was possible to detect sixiophenes in _bros_. Still, they have not been so commonly described in similar foods, and it was not possible to find information regarding their OTs in the literature.  
Another sulfur heterocycle compound detected in _bros_ was an oxathiane derivative (S6), which may refer to 1,2-, 1,3- or 1,4-oxathiane. However, considering their polarities (Log P of 1.14, 0.43 and 0.36, respectively) and the \({}^{2}\)t\({}_{\text{R}}\) of S6 (1.10 s), it was tentatively identified as 1,2-oxathiane. This compound has not been described in foods, but oxathiane derivatives have been ascribed as important aroma compounds. The most relevant example is 2-methyl-4-propyl-1,3-oxathiane, a key aroma compound of passion fruit, with a low OT of 3 \(\upmu\)g L\({}^{-1}\)[13]. Recently, this compound and 2,4,4,6-tetramethyl-1,3-oxathiane have been detected in wines [76]. Although the impact of oxathiane on the aroma of foods is currently unknown, it may impact the aroma of _bros_, and this compound is worth further study.