## 3 Results and Discussion
### Key Aroma Compounds in Non-Smoked Bacon Identified via GC-O-Ms
**} & \multirow{2}{*}{**Threshold (ug/kg)**} & \multirow{2}{*}{**Compounds**} & \multicolumn{4}{c}{**Concentration (ug/kg)**} & \multicolumn{4}{c}{**OAV**} \\ \cline{5-10}  & & & **XW** & **MN** & **ZZ** & **XW** & **MN** & **ZZ** \\ \hline
65 & 15.9 & 3-Methyl-butronic acid & 58.97 \(\pm\) 0.99 \({}^{\circ}\) & 12.03 \(\pm\) 0.23 \({}^{\circ}\) & 16.36 \(\pm\) 0.71 \({}^{\circ}\) & 3.71 \(\pm\) 0.06 \({}^{\circ}\) & 0.76 \(\pm\) 0.01 \({}^{\circ}\) & 1.03 \(\pm\) 0.04 \({}^{\circ}\) \\ \hline
66 & 1207 & Pentanoic acid & 15.3 \(\pm\) 0.71 \({}^{\circ}\) & 1.4 \(\pm\) 0.06 \({}^{\circ}\) & 4.1 \(\pm\) 0.23 \({}^{\circ}\) & 0.01 \(\pm\) 0 & - & - \\ \hline
67 & 2517.6 & Hexanoic acid & 234.84 \(\pm\) 5.36 \({}^{\circ}\) & 180.33 \(\pm\) 1.15 \({}^{\circ}\) & 44.05 \(\pm\) 2.71 \({}^{\circ}\) & 0.09 \(\pm\) 0\({}^{\circ}\) & 0.07 \(\pm\) 0\({}^{\circ}\) & 0.02 \(\pm\) 0\({}^{\circ}\) \\ \hline
68 & 640 & heptanoic acid & 1.49 \(\pm\) 0.6 \({}^{\circ}\) & 3.28 \(\pm\) 1.68 \({}^{\circ}\) & 3.97 \(\pm\) 0.73 \({}^{\circ}\) & - & 0.01 \(\pm\) 0 & 0.01 \(\pm\) 0 \\ \hline
69 & 3000 & Octanoic acid & 60.03 \(\pm\) 9.37 \({}^{\circ}\) & 25.63 \(\pm\) 1.63 \({}^{\circ}\) & 13.54 \(\pm\) 0.28 \({}^{\circ}\) & 0.02 \(\pm\) 0\({}^{\circ}\) & 0.01 \(\pm\) 0 \({}^{\circ}\) & - \\ \hline
70 & 4600 & Nonanoic acid & 27.1 \(\pm\) 0.2 \({}^{\circ}\) & 10.31 \(\pm\) 0.81 \({}^{\circ}\) & 4.9 \(\pm\) 0.08 \({}^{\circ}\) & 0.01 \(\pm\) 0 & - & - \\ \hline
71 & 130 & n-Decanoic acid & 12.27 \(\pm\) 0.59 \({}^{\circ}\) & 22.29 \(\pm\) 2.41 \({}^{\circ}\) & 19.27 \(\pm\) 1.31 \({}^{\circ}\) & 0.09 \(\pm\) 0\({}^{\circ}\) & 0.18 \(\pm\) 0.02 \({}^{\circ}\) & 0.15 \(\pm\) 0.01 \({}^{\circ}\) \\ \hline
72 & - & (E)-2  
Alcohols: A total of ten alcohols were detected in bacon samples, of which eight, five, and eight alcohols were sniffed by assessors in Yunnan, Chongqing, and Sichuan bacon, respectively. Seven alcohols could be detected only via a polar column (SH-Stabilwax-MS). The concentration in Yunnan bacon (652.59 \(\pm\) 26.12 \(\upmu\)g/kg) was also higher than that in Sichuan (577.76 \(\pm\) 2.6 \(\upmu\)g/kg) and Chongqing (344.26 \(\pm\) 34.04 \(\upmu\)g/kg) bacon. Four alcohols were considered as the main contributors to the aroma, including 1-octen-3-ol, 2,3-butanediol, 1-octanol, and 1-hexanol. The content of 1-octen-3-ol was relatively high in bacon alcohols (129.7 \(\pm\) 5.96, 72.55 \(\pm\) 1.98, and 101.94 \(\pm\) 3.28 \(\upmu\)g/kg in Yunnan, Chongqing, and Sichuan bacon). Meanwhile, 1-octen-3-ol had the highest OAV among alcohols in bacon, reaching 129.7 \(\pm\) 5.96, 72.55 \(\pm\) 1.98, and 101.94 \(\pm\) 3.28 in Yunnan, Chongqing, and Sichuan bacon, respectively. Other alcohols did not have a significant contribution due to the low FD factor, even 2-ethyl-1-hexanol could not be sniffed. Although alcohols were not the most abundant volatiles, they were also vital to the formation of the bacon aroma [22]. It differs from this study, possibly due to the different raw materials. Previous research indicated that 2,3-butanediol was the main alcohol in the loin and chorizo. 1-Octen-3-ol was the most prominent alcohol found in the three bacon samples and had the highest FD factor in Chongqing and Yunnan bacon. This volatile compound might be the oxidative product of linoleic or other polyunsaturated fatty acids, and it imparts a strong mushroom and earthy aroma to bacon. 1-hexanol had a high FD factor in Yunnan bacon and was considered a hexanal reduction product [23]. In Sichuan bacon, 1-octanol exhibited a high FD factor that was due to the oxidation of oleic acid [24]. These compounds provide herbal and fatty notes and are related to sweet and fruity aromas with certain concentrations [25]. The GC-O-MS analysis detected mostly linear alcohols derived from the oxidation of fatty acids. Conversely, branched alcohols were likely produced through the Strecker degradation of amino acids or the reduction of branched-chain aldehydes [22].