# Characterization of the Aroma Profile of Food Smoke at Controllable Pyrolysis Temperatures
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline
**No.** & **RI** & **Compound** & **Odor Description 1** & **Quantifier Ion _m/z_** & **Identification** \\ \hline furans & & & & & \\
5 & 1445 & furfural & sweetish, woody, almond-like, & & 97 & RI, MS \\
6 & 1553 & 5-methyl-furfural & spicy, caramel-like, maple-like & 111 & RI, MS \\ lactones & & & & & \\
7 & 1600 & butylolactone & creamy, oily, fatty, caramel-like & 42 & RI, MS \\
8 & 1742 & 2-(5H)-furanone & butter-like & 55 & RI, MS \\ phenols & & & & & \\  & & & & & \\
9 & 1838 & guaiaicol & spicy, clove-like, vanilla-like, & & \\  & & & & phenolic, medicinal, leathery, & 109 & RI, MS \\  & & & & woody, smoky & & \\
10 & 1933 & creosol & spicy, clove-like, vanilla-like, & & \\  & & & & phenolic, medicinal, leathery, & 138 & RI, MS \\
11 & 1982 & phenol & musty, phenolic, plastic-like, & & 94 & RI, MS \\  & & & & medicinal, herbal, leathery & & \\
12 & 1982 & _o_-cresol & musty, phenolic, plastic-like, & & 108 & RI, MS \\  & & & & medicinal, herbal, leathery & & \\
13 & 2007 & 4-ethylguaiaicol & spicy, smoky, bacon-like, phenolic, & & 137 & RI, MS \\  & & & & clove-like & & \\
14 & 2058 & _p_-cresol & phenolic, narcissus-like, animalic, & & 107 & RI, MS \\  & 15 & 2143 & eugenol & sweetish, spicy, clove-like, woody & & 164 & RI, MS \\
16 & 2237 & syringol & smoky, phenolic, balsamic, & & 154 & RI, MS \\  & & & & & \\
17 & 2317 & _trans_-isoeugenol & sweetish, spicy, caramation-like, & & & \\  & & & & phenolic, floral & & \\
18 & 2522 & vanillin & sweetish, vanilla-like, creamy, & & & \\  & & & chocolate-like & & \\ \hline \end{tabular} \({}^{1}\) Odor descriptions from The Good Scent Company (2021).  
\end{table} 
Table 1: _Cont._structures released from hemicelluloses and celluloses during thermal degradation [35]. As part of the primary pyrolysis from cellulose and cellobiose, furans are formed already at low temperatures and are not expected to have higher transformation rates with increased temperatures [36]. Furfural and its homologs may also play an important role in the development of food smoke flavor and their odor is described as sweetish and caramel-like [2; 32]. Phenols are released during thermal degradation of lignin, which shows its peak at about 350 \({}^{\circ}\)C [6; 12; 13; 14; 15]. Consequently, we expected an increased phenol content in our studies from the pyrolysis temperature of 450 \({}^{\circ}\)C. In our study the substance class phenols showed a very strong increase in peak area with increasing pyrolysis temperature over the entire temperature range (150-900 \({}^{\circ}\)C) observed (Figure 1). The peak area at a pyrolysis temperature of 900 \({}^{\circ}\)C was significantly higher than at 600 \({}^{\circ}\)C and 750 \({}^{\circ}\)C. No significant difference between 600 \({}^{\circ}\)C and 750 \({}^{\circ}\)C might be attributed to fluctuations in the smoking process. However, an increase trend could be obtained from the results of previous studies; a temperature dependence in phenol production in smoke can be deduced. The results of certain research show a proportional increase in phenol content in smoke when the temperature is increased up to 400 \({}^{\circ}\)C and 600 \({}^{\circ}\)C, respectively [37; 31]. Investigations at a higher pyrolysis temperature range (400-1050 \({}^{\circ}\)C) reinforced this increase in phenol area in the lower temperature range and showed a peak at 600-700 \({}^{\circ}\)C [16]. The phenols form the most important group of substances regarding the formation of the typical smoke aroma, and primarily exhibit smoky, woody and spicy odor notes [6]. The substances guaiacol, \(p\)-cresol, syringol, isoeugenol, \(o\)-cresol and eugenol, which were also investigated here, were shown to be suitable marker substances for food smoke [38]. Figure 1: Absolute peak areas with standard deviation of the substance classes carbonyls, furans and lactones in food smoke depending on pyrolysis temperature.