# Characterization of the Aroma Profile of Food Smoke at Controllable Pyrolysis Temperatures
## 3 Results and Discussion
### Effect of Pyrolysis Temperature on the Area and Ratios of Individual Phenols and Lactones
Looking at the same temperature range, these findings do not coincide with ours. However, pure smoke and smoked products are only comparable to a limited extent, since various factors influence the absorption of food smoke compounds into the product matrix, such as the moisture of the surface, the casing and the nature of the product matrix [5; 41; 42]. Figure 4: Absolute peak areas with standard deviation of individual phenols in food smoke depending on pyrolysis temperature. (**a**) Gunaicol, (**b**) syring, (**c**) phenol, (**d**) crossol, (**e**) +ethyl-guasicol, (**f**) \(p\)-crossol, (**g**) eugenol, (**h**) \(o\)-crossol, (**f**) vnullin and (**j**) _trans-isocugenol_. Different letters indicate a significant difference in absolute peak area of a substance between different pyrolysis temperatures (\(p<0.05\), \(n=3\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Pyolysis temperature [°C]** & \multicolumn{4}{c}{**Relative Peak Area [\%]**} \\ \hline  & **gaiaacol** & **synignol**ol**ol & **phenol** & **creosol** & **4-ethyl-gaiaacol** \\ \hline
150 & 17.17 \(\pm\) 6.39 & 35.10 \(\pm\) 12.10 \({}^{\rm ab}\) & 3.79 \(\pm\) 1.06 \({}^{\rm ab}\) & 13.79 \(\pm\) 4.20 & 10.39 \(\pm\) 1.88 \\
300 & 11.82 \(\pm\) 3.92 & 36.38 \(\pm\) 10.59 \({}^{\rm ab}\) & 2.96 \(\pm\) 0.66 \({}^{\rm ab}\) & 11.66 \(\pm\) 3.08 & 10.84 \(\pm\) 2.18 \\
450 & 7.43 \(\pm\) 0.80 & 40.72 \(\pm\) 1.38 \({}^{\rm b}\) & 2.88 \(\pm\) 0.23 \({}^{\rm a}\) & 10.29 \(\pm\) 0.63 & 10.88 \(\pm\) 0.37 \\
600 & 7.94 \(\pm\) 0.64 & 38.24 \(\pm\) 1.04 \({}^{\rm b}\) & 3.16 \(\pm\) 0.21 \({}^{\rm a}\) & 10.94 \(\pm\) 0.42 & 11.15 \(\pm\) 0.24 \\
750 & 8.15 \(\pm\) 0.79 & 37.37 \(\pm\) 0.97 \({}^{\rm b}\) & 3.16 \(\pm\) 0.21 \({}^{\rm a}\) & 11.16 \(\pm\) 0.41 & 11.51 \(\pm\) 0.12 \\
900 & 9.41 \(\pm\) 0.78 & 31.95 \(\pm\) 1.05 \({}^{\rm a}\) & 4.73 \(\pm\) 0.21 \({}^{\rm b}\) & 12.11 \(\pm\) 0.42 & 11.82 \(\pm\) 0.21 \\ \hline
**Pyolysis temperature [°C]** & \multicolumn{4}{c}{**Relative Peak Area [\%]**} \\ \multicolumn{4}{c}{_P-_**cresol**} & **evgenol** & **o-_cresol** & **vanillin** & **trans-isogenized** \\ \hline
150 & 1.93 \(\pm\) 0.35 \({}^{\rm a}\) & 2.52 \(\pm\) 0.09 \({}^{\rm a}\) & 1.62 \(\pm\) 0.49 \({}^{\rm b}\) & 2.18 \(\pm\) 1.38 & 1  
Lactones, such as carbonyls and furans, are also associated with hemicellulose and cellulose degradation, which take place from 200 to 260 \({}^{\circ}\)C and from 280 to 320 \({}^{\circ}\)C, respectively [6; 13; 14; 15]. During the pyrolysis of hemicellulose, the glycosidic bonds and C-C bonds in the pyranose ring are dissolved first, releasing subunits. These are dehydrogenated at a temperature of 275-290 \({}^{\circ}\)C, resulting in the formation of furfural. These dehydration processes also produce compounds with keto groups and y-lactones, such as the 2-(5H)-furanone and butylolactone studied here [12]. 2-(5H)-Furanone increased significantly during the increase in temperature (Table 3). These increases occurred in steps when the pyrolysis temperature was raised from 150 \({}^{\circ}\)C to 300 \({}^{\circ}\)C, and another increase occurred when the pyrolysis temperature was raised from 600 \({}^{\circ}\)C to 750 \({}^{\circ}\)C (Figure 5a). Butyrolactone is significantly higher at pyrolysis temperatures of 300 \({}^{\circ}\)C, 600 \({}^{\circ}\)C and 900 \({}^{\circ}\)C compared to temperatures of 150 \({}^{\circ}\)C and 450 \({}^{\circ}\)C (Figure 4b). A linear increase with increasing pyrolysis temperature cannot be deduced. Considering the relative peak areas to analyze the ratio of 2-(5H)-furanone and butylolactone to each other of both lactones, only the temperatures 300 \({}^{\circ}\)C and 150 \({}^{\circ}\)C differed significantly.