# The Impact of Different Cooking Methods on the Flavor Profile of Fermented Chinese Spicy Cabbage
## 2 Results and Discussion
### Comparison of the KACs and Possible Pathways  
To further distinguish the main flavor compounds and their conveyed odors between different groups, the KAC differences among the three CSC samples were further screened based on the analysis of OAV (OAV > 1) and fold change (FC > 2 or <0.5). The histograms show the VFCs with greater than two-fold change, and the newly generated or disappeared (Figure 3a,b), indicating a significant change in flavor compounds after cooking. Figure 3: _Cont._  
Figure 3: KACs (OAV > 1) in CSC samples under different cooking methods. (**a**) KACs with FC > 2 or <0.5, and newly generated or disappeared VFCs (BL-CSC vs. CK-CSC). (**b**) KACs with FC > 2 or <0.5, and disappeared or newly generated VFCs (SF-CSC vs. CK-CSC). (**c**) The potential markers responsible for the aroma differences and their OAV changes among the three CSC samples. The screening criteria were OAV > 1, and FC > 2 or <0.5, newly generated or disappeared. Abbreviations: KACs, key aroma compounds; OAV, odor activity value; CSC, Chinese spicy cabbage; FC, fold change; VFCs, volatile flavor compounds; CK-CSC, the CSC without thermal processing group; BL-CSC, boiled CSC; SF-CSC, stir-fried CSC. Comparing BL-CSC with CK-CSC (Figure 3a), three KACs (linalool, geranyl acetate, and nonanal) were newly generated after boiling, contributing sweet and fatty odors to BL-CSC. Meanwhile, four KACs including (_E_)-2-decneal, diallyl sulfide, (_E_,_E_)-2,4-decadienal, and dimethyl disulfide disappeared after boiling, resulting in the lack of waxy, sweet, and onion odor compared with CK-CSC. And seven KACs including _cis_-propenyl propyl disulfide, diallyl disulfide, \(\beta\)-sesquiphellandrene, diallyl trisulfide, dimethyl trisulfide, (_E_)-\(\beta\)-ionone, and allyl methyl disulfide were significantly reduced (FC \(<\) 0.5) in BL-CSC, which reduced the pungent, herbal, garlic, cabbage, and seaweed odor to a certain extent. Comparing SF-CSC with CK-CSC (Figure 3b), the newly generated (_E_)-2-nonanal, octanal, 1-octen-3-ol, nonanal, and 1-octen-3-one after stir-frying gave SF-CSC green, fatty, and mushroom odors. Acetic acid and (_E_)-2-decneal with FC \(>\) 2 increased the SF-CSC acidic and orange odor contrasted with CK-CSC. Meanwhile, (_E_)-\(\beta\)-ionone and \(\beta\)-sesquiphellandrene disappeared resulting in reduced fruity odor of SF-CSC. And five KACs including dimethyl trisulfide, dipropyl disulfide, cis-propenyl propyl disulfide, 2-phenethyl isothiyanate, and diallyl trisulfide that decreased by greater than two-fold were all sulfides, which would reduce the cabbage, burnt green onion, radish, pungent, and garlic odor in SF-CSC. The KACs increased and newly generated in SF-CSC were more than those in BL-CSC, with more abundant odor changes, which was due to higher cooking temperature, and the peanut oil added in the stir-frying process that was related to the increase of aldehydes, acids, and alcohols [44; 51; 53]. The potential markers causing aroma differences among the three CSC samples were screened by analyzing VFCs with OAV \(>\) 1, and FC \(>\) 2 or \(<\)0.5, newly generated or disappeared as shown in Figure 3c. Five VFCs were selected as the potential KACs to distinguish the different CSC samples, including diallyl trisulfide, nonanal, (_E_)-\(\beta\)-ionone, \(\beta\)-sesquiphellandrene, and (_E_)-2-decneal. The possible formation pathways of KACs after cooking are shown in Figure 4. It was suggested that boiling may facilitate the dissolution and extraction of geranyl acetate, leading to its increase in BL-CSC. Geraniol was produced by thermal degradation of geranyl acetate under acidic conditions and the main product from geraniol during acid-catalyzed transformation was linalool [54]. Sulfides mainly originated from degradation of sulfur-containing amino acids in vegetables, also allicin and deoxyallin in garlic [24; 55]. The reduction in sulfides might be due to the thermal treatment.