## 3 Results
### GC-IMS Analysis
#### 3.1.2 Volatile Compounds Analysis  
GC-IMS is a novel separation and detection technology with the advantages of sensitivity, accuracy, and rapidity, which can be applied to the determination of aroma compounds in yellow horn seed oil [29]. A total of 178 chromatographic signals have been detected by using GC-IMS, leading to the identification of 97 aroma compounds in the GC-IMS database. These compounds consisted of 23 aldehydes, 19 alcohols, 17 ketones, two acids, 17 esters, seven sulfur-containing compounds, one furan heterocyclic compounds, three hydrocarbons, seven pyrazine heterocyclic compounds, and one other compound (Figure S1A). Meanwhile, some compounds exhibit multiple signals (monomer and dimer) due to the addition of ions and neutral molecules in GC-IMS [30]. These compounds have similar retention times but different drift times. Further details regarding the VOCs are presented in Table S1.  
Aldehydes, which contribute to the roasted and fatty aroma, are key compounds found in plant raw materials such as peanuts and canola oil [31]. In yellow horn seed oil, aldehydes were the most abundant VOCs detected via GC-IMS, accounting for 23.71% of the total, followed by alcohols (19.59%) and ketones (17.53%) (Figure 3A). From Figure 3B, it can be seen that the content of aldehydes increased significantly with the increase in roasting temperature within a certain temperature range, such as 2-octenal (isomer), 2-heptenal (isomer), and nonanal (\(p<0.05\)). The formation of these compounds is related to lipid oxidation. For instance, nonanal, octanal, and decanal are produced via the auto-oxidation of oleic acid (C1:18), generating 10-hydroperoxides and 11-hydroperoxides, and/or secondary formation of 8-hydroperoxide [32]. The findings suggest that the heating process of yellow horn seed leads to lipid oxidation, which leads to the formation of these aroma compounds. Alcohols could be produced via the oxidation of polyunsaturated fatty acids catalyzed by lipoxygenase [33; 34]. Meanwhile, the amino acid derivation pathway was also an essential source of some alcohols [35]. For instance, phenylethyl1 alcohol could be synthesized from phenylalanine by the action of aromatic amino acid aminotransferase (AAAAT) [36]. Phenylethyl alcohol was found in low content. In contrast, the concentration of 1-octen-3-ol was higher, indicating that the alcohol was produced, presumably, via fat oxidation or aldehyde reduction in yellow horn seed oil roasted at different temperatures. This result was consistent with [PERSON] et al.'s [14] opinion of the results in their study concerning walnut oil. Ketones are typically produced through the decomposition of amino acids and thermal oxidative degradation of polyunsaturated fatty acids [14]. As shown in Figure 3B, the ketone content tended to increase and then decrease with increasing temperature. The sample at 150 \({}^{\circ}\)C had the highest content, while that at 120 \({}^{\circ}\)C had the lowest. Seven sulfur-containing compounds, including dimethyl disulfide, dimethyl trisulfide, and diethyl disulfide, have been detected in yellow horn seed oil. These findings were consistent with previous reports, which identified dimethyl trisulfide as one of the important aroma compounds in their analysis of fragrant rapeseed oil [10].