## 3 Results and Discussion
### Analysis of Aroma-Active Volatiles by GC-MS-O
In FXZH, 11 aroma-active compounds were identified, including two with strong OI, five with middle OI, and four with weak OI. Among them, nonanal (B3) and 2,6-dimethylpyrazine (H1) were noted for their strong OI, with similar findings in SXZH. Despite 2,6-dimethylpyrazine (H1) being present in all five ham samples, it was perceived with strong intensity only in FXZH and SXZH, suggesting it may be a key compound distinguishing Xuanwei hams. For Jinhua hams (LTWH and FZWH), 23 aroma-active compounds (12 for LTWH and 18 for FZWH) were identified. Among them, 1-hexanol (A2), nonanal (B3), and heptanal (B17) were considered the more important aroma-active compounds, along with three unknown compounds (UC8, UC9, and UC10). The hedonic assessment was conducted by the panelists to evaluate the relative pleasantness or unpleasantness of the aroma-active compounds, using a scale ranging from 1 (completely dislike) to 10 (very good, pleasant, and agreeable). Among the identified compounds, 1-octanol (A7), nonanal (B3), 3-octanone (D3), 5-ethyldihydro-2(3H)-Furanone (D4), dihydro-5-pentyl-2(3H)-furanone (D6), 5-butyldihydro-2(3H)-furanone (D8), 2-pentylfuran (H2), and two unknown compounds (UC1 and UC10) all received scaled values higher than 6, suggesting they contribute positively to the sensory attributes of the dry-cured hams. Notably, 3-Octanone (D3) was unique to BHCH (the most expensive ham), while 1-octanol (A7) and 2-pentyl-furan (H2) were exclusive to SXZH (the second most expensive ham). These compounds might be key factors influencing the price differences among the five dry-cured hams. In BHCH, 17 aroma-active compounds were detected, with 9 also found in SXZH, 6 in FXZH, 6 in LTWH, and 9 in FZWH. Despite SXZH and FZWH having similar odor compositions to BHCH, the latter showed a more favorable aroma profile as evaluated by the sensory panel. This phenomenon could be due to the adverse effect of unpleasant odors which were evaluated by the panelists. In the experiments, aroma-active compounds with scaled values lower than four were regarded as unpleasant odors. Table 5 shows that there were two unpleasant odors in BHCH, while SXZH and FZWH had five unpleasant odors. A high profile of unpleasant odors contributes to the off-odor in dry-cured hams, which is considered the main quality defect of dry-cured hams [71]. To further highlight the differences in aroma-active compounds among the five dry-cured hams, a PCA was performed using the hedonic assessment data. A PCA is a statistical tool used to intuitively show the data distribution in a low-dimensional space by extracting meaningful information from the raw data, allowing data to be grouped according to the similarity of the input characteristics to determine the distance between classes. The high separation between clusters indicates effective classification, while overlap suggests less distinction. The PCA extracted four principal components with eigenvalues greater than one, accounting for a cumulative contribution rate of 94.59%. The first component (PC1) and the second one (PC2) explained 35.6% and 25.2%, respectively, and the projections of these two primary components for the ham samples are shown in Figure 6. PC1, the most significant variable, was positively correlated with most aroma-active compounds with hedonic values higher than six (excluding one unknown compound, UC10). The two most expensive hams (BHCH and SXZH) were positioned on the positive PC1 axis, while the other three (FXZH, LTWH, and FZWH) were on the negative PC1 axis, indicating that PC1 can preliminarily distinguish between hams of different price points. These results suggest a positive correlation between aroma-active compounds with high hedonic scores and the price of dry-cured hams. Furthermore, the PCA showed clear separation among the five ham types, demonstrating the effectiveness of combining a PCA with a GC-O analysis to discriminate odor attributes.