## 3 Results and Discussion
### Analysis of Aroma-Active Volatiles by GC-MS-O
The GC-MS-O analysis revealed that the aromacative compounds identified in dry-cured harms covered a broad range of aroma groups, including \"woody/resinous\", \"pungent\", \"chemical\", \"popcorn\", \"fruit, other than citrus\", \"lemon\", \"minity\", \"sweet\", \"sickening\", and \"floral\". Among these aroma groups, \"woody/resinous\", \"chemical\", \"popcorn\", and \"sweet\" were the most frequently noted. Among these 29 aroma-active compounds, three compounds, namely nonanal (B3), 5-butyldihydro-2(3H)-furanone (D8), and 2,6-dimethylpyrazine (H1), were identified in all five ham samples. These three compounds contribute to the \"sweet\" and \"popcorn\" odor, which may generally influence the overall aroma of the harms. Nonanal (B3) is a major aldehyde derived from the oxidative degradation of unsaturated fatty acids, particularly oleic acid, during the curing and aging process. It has a low odor threshold, making it a critical compound in the perception of matured meat products [45]. 5-Butyldihydro-2(3H)-furanone (D8), belonging to the lactone/furanone family, likely forms via thermal degradation of carbohydrates or Maillard-type reactions involving reducing sugars and amino acids during long-term aging [68]. 2,6-Dimethylpyrazine (H1) is typically generated from Maillard reactions involving amino acids and reducing sugars during the drying and ripening stages. It is frequently reported in various cured and cooked meat products [48]. By comparing the concentration of aroma-active compounds, it is noteworthy that one compound identified by GC-MS in several ham samples might not necessarily be detected by panel assessors in all these samples. For example, 1-octanol (A7) was detected in BHCH, SXZH, and FZWH by GC-MS, with the highest concentration in SXZH compared to BHCH and FZWH. However, the GC-MS-O analysis revealed that 1-octanol (A7) was only detected in SXZH by the panel assessor. This discrepancy could be attributed to the detection threshold of aromas, which is the lowest concentration at which humans can perceive the aroma [69]. It is evident that the intensity of aroma-active compounds generally increased with their concentration, consistent with findings from previous studies [19]. Compounds with strong OI were considered more significant aroma-active compounds than those with middle or weak odor intensities. In BHCH, 17 aroma-active compounds (3 with strong OI, 10 with middle OI, and 4 with weak OI) were identified. Among them, 2-heptanol (A1), 1-hexanol (A2), and nonanal (B3) were identified as the most important, contributing to \"woody/resinous\", \"pungent\", and \"sweet and popcorn\" odors, respectively. Notably, 2-heptanol (A1), a secondary alcohol with woody and resinous aroma descriptors, was exclusively detected in BHCH and SXZH. These two hams, although differing in origins, are both considered premium products and share several processing attributes associated with high-end dry-cured ham production, such as long ripening periods (12-36 months), controlled cellar aging, and refined salting protocols. The presence of 2-heptanol (A1) may reflect advanced lipid oxidation and secondary alcohol formation, which are more likely to occur in well-matured hams due to prolonged exposure to enzymatic and oxidative processes [70]. In SXZH, 20 aroma-active compounds were identified, with 7 having strong OI, 12 with middle OI, and 1 with weak OI. SXZH had the highest number of both aroma-active compounds and those with strong OI among the five dry-cured harms, indicating a more complex odor profile. According to the odor evaluation, the \"pungent\" odor might be caused by the presence of 1-hexanol (A2); the \"fruit, other than citrus\" odor was linked to the presence of 2-nonanol (A10); the \"sweet\" and \"popcorn\" were mainly caused by nonanal (B3) and 2,6-dimethylpyrazine (H1); and the \"woody/resinous\" odor was associated with 2-heptanol (A1) and 2-nonanone (D2). Furthermore, one unknown aroma-active compound (UC5) contributed to the \"wood/resinous\" and \"chemical\" odor.