## 3 Results and Discussion  
### Volatile Profile  
A total of 40 volatile compounds were identified in the analyzed samples (Table 1), of which 3 appeared to be exclusive to grilled samples: furfural, furfuryl alcohol and pyrrole. The volatile profile of raw meat alternatives (RMA), without addition of myoglobin (Mb), consists mainly of hydrocarbons and 2-pentylfuran, which account for 34.0 \(\pm\) 6.7% and 29.7 \(\pm\) 2.2% of the total peak area respectively, followed by alcohols (13.7%) and unsaturated aldehydes (12.0%). Grilling the plant-based meat alternatives (GMA) is associated with a significant decrease in alcohol and cyclic aldehyde content, in favor of the formation of branched aldehydes, ketones, phenols and most notably pyrazines. Despite this shift in volatile fractions, the grilling process does not significantly affect the total peak area of volatiles present in RMA compared to GMA. However, addition of myoglobin (Mb) leads to significant (\(p<0.05\)) formation of various odor-active volatile compounds. Statisticalanalysis further indicates a significant interaction between effects of Mb addition and grilling (%Mb \(\times\) G) on the total peak area, suggesting that a synergetic relationship exists between both factors. A total of 11 saturated and unsaturated aldehydes are identified in the plant-based meat alternatives, supplemented with Mb. Most of these aldehydes are typically associated with (auto-)oxidation of unsaturated fatty acids in food matrices [27]. Due to their low odor thresholds, aldehydes are known to greatly impact the aroma of meat and meat products. Of all classes of chemical compounds, the peak area of saturated aldehydes displays the most pronounced increase with rising Mb concentrations, making them the dominant fraction of the volatile profile in Mb-enriched samples. In RMA + 1.0%Mb and GMA + 1.0%Mb, they respectively make up 36.9 \(\pm\) 1.0% and 30.2 \(\pm\) 1.3% of the total peak area. Hexanal is the most abundant aldehyde in the analyzed samples. In high concentrations, it imparts an unpleasant rancid odor, but at low levels it is characterized by a pleasant, grassy aroma and generally contributes to a desired aroma in meat products [28; 29]. RMA contains high initial levels of hexanal (10.6 \(\pm\) 1.3% of the total peak area), which may originate from the soy protein used to prepare the burgers. This aldehyde is reported as the predominant volatile compound in soybeans, accounting for 40.9% of the total volatile profile of the ingredient [30]. Grilling found to reduce the amount of hexanal in GMA. Hexanal can also be formed as an oxidation product of linoleic acid and is often considered as an excellent indicator of lipid oxidation in metals and meat products rich in n-6 polyunsaturated fatty acids [31]. Addition of Mb in both RMA + Mb and GMA + Mb leads to considerable increases in hexanal content which greatly exceeds the decrease caused by the grilling process in GMA. Additionally, the highest peak areas for hexanal are found in GMA + Mb. This suggests that the addition of Mb has a significant (\(p<\) 0.01) influence on the degree of lipid oxidation in RMA + Mb and GMA + Mb, which is further amplified by the heat of the grilling treatment. Further research is required to determine whether these hexanal concentrations exceed rancid odor thresholds or remain within a desirable range. Among other identified aldehydes, heptanal and nonanal (saturated aldehydes derived from oleic acid), and unsaturated aldehydes exhibit similar, increasing tendencies in relation to Mb concentration. Branched aldehydes (2- and 3-methylbutanal), on the other hand, originate from proteolysis and degradation of amino acids [27], and exhibit an opposite behavior, whereby they decrease as the Mb content increases in both raw and grilled samples.