## 3 Results and Discussion  
### Volatile Compounds Analysis  
The volatile compounds identified in the five different dry-cured hams (BMCH, SXZH, FXZH, LTWH, and FZWH) using HS-SPME-GC-MS-O are listed in Table 4. A total of 78 volatile compounds were identified and semi-quantified, and these were classified into eight chemical families: alcohols, aldehydes, alkanes, ketones, esters, acids, terpenes, and others. As shown in Table 4, the number of identified volatile compounds varied among the samples: 38 for BMCH, 41 for SXZH, 39 for FXZH, 30 for LTWH, and 41 for FZWH. SXZH and FZWH had the highest number of identified volatile compounds, while LTWH and FZWH exhibited the greatest variety of compounds. A Venn diagram based on the profiles of volatile compounds across the different ham samples is shown in Figure 5. A total of nine volatile compounds were identified in all five ham samples, namely nonanal (B3), benzaldehyde (B4), phenylethyl alcohol (A8), 2,6-dimethylpyrazine (H1), phenylacetaldehyde (B7), dodecane (C3), dihydro-5-pentyl-2(3H)-furanone (D6), 5-butyldihydro-2(3H)-furanone (D8), and tetradecane (C5). Among the nine volatile compounds, nonanal (B3) and benzaldehyde (B4) were the most abundant overall. These compounds are typically generated via the \(\beta\)-oxidation and autoxidation of unsaturated fatty acids during the early stages of drying and throughout the cellar-aging process [25]. Nonanal (B3) and benzaldehyde (B4) showed particularly high concentrations in both SXZH and FZWH, indicating more extensive lipid oxidation in these samples due to their longer maturation times or higher fat degradation levels. Phenylethyl alcohol (A8), a secondary alcohol often associated with amino acid metabolism or the further oxidation of aldehydes [26], was found in significantly higher concentrations in SXZH than in other samples. This may reflect either prolonged proteolysis or deeper oxidative transformation pathways during the longer maturation periods of the products. Specific volatile compounds were unique to each ham type: three to BHCH, nine to SXZH, six to FXZH, and six to FZWH. SXZH had the largest number of specific volatile compounds, while LTWH possessed no specific volatile compounds. These unique volatile compounds may originate from distinct differences in raw materials, microbial flora, and processing conditions. Volatile compounds (i.e., 2,4-dimethyl-heptane, 3-octanone, and (E)-2-heptenal) were identified only in BHCH. The exclusive presence of 2,4-dimethyl-heptane and (E)-2-heptenal in BHCH could be associated with the oxidative degradation of unsaturated fatty acids under Spanish-style cellar-aging at lower humidity, which favors lipid autoxidation and long-chain alkane fragmentation [27]. Volatilecompounds such as 2-pentyl-furan, 2,4-dimethyl-hexane, 2-nonanol, 2-tetradecanone, trade-canal, nonanoic acid ethyl ester, 1-tetradecanol, amyl cyclopentenone, and acetic acid hexyl ester were identified only in SXZH. The higher number of unique volatiles in SXZH may reflect its extended 36-month cave maturation and distinct microbial enzymatic activities, which are known to catalyze esterification and alcohol formation. Moreover, hexanoic acid ethyl ester, 3,5-octadien-2-one, 2,2,4,4,6,8,8-heptamethyl-nonane, 3,7-dimethyl-1-octanol, tetramethyl-pyrazine, and dimethyl trusulfide were identified only in FXZH. Tetramethyl-pyrazine and dimethyl trusulfide are likely linked to Maillard reaction pathways and sulfur amino acid catabolism during protein degradation under prolonged ripening. Volatile compounds such as 3-octen-2-one, acetic acid, ethanol, (E)-2-octen-1-ol, cis-4-decenal, and (1S, cis)-4,7-dimethyl-1,2,3,5,6,8a-hexahro-naphthalene were identified only in FZWH. Previous studies have shown that the overall odor quality of hams can be characterized by several volatile compounds ([PERSON] et al., 2022) [2]. Therefore, the specific volatile compounds contribute to the distinct characteristics and flavor profiles of the different dry-cured hams.