## 3 Results and Discussion
### Volatile Compounds Analysis
expensive hams, respectively, shared nine alcohols, excluding 2-heptanol (A1), ethanol (A14), and (E)-2-octen-1-ol (A15). 2-Heptanol (A1) was unique to BHCH and was the most abundant alcohol in this sample (1816.45 \(\pm\) 5.39 ng/g). Ethanol (A14) and (E)-2-octen-1-ol (A15) were only present in FZWH, albeit in low concentrations (359.18 \(\pm\) 3.18 ng/g and 217.8\(\pm\)3.43 ng/g, respectively). As reported in previous reports, ethanol (A14) is not significantly known for its aroma [37]. Thus, 2-heptanol (A1) likely plays a key role in differentiating BHCH from FZWH. SXZH, the second most expensive ham, had seven alcohols, which were also detected in BHCH. The unique presence of 2-Nonanol (A10) in SXZH may aid in the identification of SXZH among the five hams. Conversely, 1-octen-3-ol (A3), one of the alcohols with low thresholds, was detected in BHCH but not in SXZH, suggesting it may be a distinguishing factor between BHCH and SXZH. Among the detected volatile compounds, aldehydes were the most abundant group, with eighteen aldehydes identified in this study. Aldehydes are significant degradation products of lipid oxidation, but they can also arise from Maillard-induced amino acid degradation [38]. Aldehydes play an important role in the overall flavor of dry-cured hams because of their low odor thresholds, high concentrations, and distinctive characteristic odors (e.g., sweet, floral, pungent notes) [2; 31; 39; 40]. Among the aldehydes, nonanal (B3), benzaldehyde (B4), and phenylacetaldehyde (B7) were present in all ham samples. Nonanal (B3), a common volatile compound in meat products, is a linear-chain aldehyde that contributes to sweet and fruity aromas [41]. Other typical linear-chain aldehydes, such as hexanal (B1), octanal (B2), decanal (B13), and heptanal (B17) were also detected in the ham samples. These linear aldehydes are mainly generated from the degradation of long-chain fatty acids [42; 43]. Hexanal (B1), found in BHCH, FXZH, LTWH, and FZWH, was the most abundant aldehyde among the four hams (7859.9 \(\pm\) 19.9 ng/g, 3310.9 \(\pm\) 6.49 ng/g, 638.9 \(\pm\) 0.67 ng/g, and 13283.48 \(\pm\) 29.52 ng/g, respectively). In general, hexanal (B1) is known as a major oxidation product in dry-cured meats and serves as a good indicator of oxidation levels [18; 44; 45]. The high concentrations of hexanal (B1) observed align with the findings from studies on Istrian and Iberian hams [38; 46]. Octanal (B2) was detected in BHCH, LTWH, and FZWH but not in Xuanwei hams (SXZH and FXZH), likely due to differences in spice additions during the manufacturing process. Another important aldehyde detected in the dry-cured ham was the branched-chain saturated aldehyde, resulting from the Strecker degradation of amino acids like valine and leucine [7; 40; 47], including benzaldehyde (B4), phenylacetaldehyde (B7), and 3-methylbutanal (B16). These aldehydes increase during fermentation and contribute green, honey, fatty, and chocolate-like odors, enhancing the meaty odor and reducing sour notes [40; 48]. 3-Methylbutanal (B16), a major contributor to Istrian dry-cured ham flavor [49; 50], was found in FXZH, LTWH, and FZWH. Alkanes are usually formed by the oxidation of unsaturated fatty acids [2]. Herein, 14 alkanes were detected. Alkanes generally contribute minimally to the overall flavor of dry-cured hams due to their high thresholds [6; 35]. In this study, the concentration of the detected alkanes was relatively low compared to the major compound groups like alcohols and aldehydes. Notably, BHCH exhibited a significantly higher concentration of 2,4-dimethyl-heptane (C1) at 2940.23 \(\pm\) 14.08 ng/g, which was not detected in the other samples. This suggests a unique lipid oxidation pathway or raw material characteristic specific to BHCH. Similarly, SXZH showed a markedly elevated level of 2,4-dimethyl-hexane (C7) at 4748.34 \(\pm\) 18.47 ng/g, indicating a distinct oxidative process possibly influenced by its extended maturation period of 36 months.