## 3 Results and Discussion
### Analysis of Volatile Compounds Obtained by GC-MS  
Table S1 shows the details of volatile compounds identified by GC-MS. Of these, 49 compounds were characterized, of which 7 were defined as food additive classes in Pubchem ([[https://pubchem.ncbi.nlm.nih.gov/](https://pubchem.ncbi.nlm.nih.gov/)]([https://pubchem.ncbi.nlm.nih.gov/](https://pubchem.ncbi.nlm.nih.gov/)), accessed 1 March 2022), and 35 were recorded with flavor descriptions. The types of volatile substances increased with the increase in time. A total of 11 types were found in 0 days, 24 in 7 days, 26 in 14 days, 27 in 21 days, 33 in 28 days, 27 in 35 days, and 31 in 42 days. As the end of the fermentation time on the 42 nd day was reached, each volatile component maintained the state of esters (16) > aldehydes (6) > acids (4) > alcohols (3) > ketones (2). Aldehydes are the significant by-products of lipid oxidation. However, Maillard-induced amino acid degradation also produces some aldehydes. They often have a significant impact on the characteristic flavor of dry-cured ham due to their low odor thresholds [12; 39]. A total of 8 aldehyde compounds are shown in Table S1. Decanal, nonanal and dodecanal are acyclic aliphatic aldehydes with sweet floral and fruity aromas [24]. Nonanal is generally considered the main oxidation product in dry-cured meat products and may exhibit fruit, green apple, and vegetable odors [25; 40].henylacetaldehyde is a Strecker aldehyde that imparts a honey-like odor to ham [36], while benzaldehyde exhibits bitter almonds, cherry, and nutty aromas. As shown in Table S1, ketones mainly include four compounds. Ketones are thought to result from lipid oxidation [41]. In the present study, methyl ketones, including 2-nonyl ketone and methyl nonyl ketone, were formed through chemical reactions in the presence of a large number of microorganisms, which were described as essential contributors to the complex flavor and aroma attributes of pork [12; 42]. Still, except for 2-Undecanone and 2-Nonanone, the contents of other ketones were not high. Reports show that high levels of ketones are a symptom of poor quality dry-cured ham. Figure 3: Concentrations of 17 FAA (**A**) and taste activity value (TAV) of various taste amino acids and total TAV (TTAV) at different times (**B**). Alcohols are volatile compounds with sweet, fruity, or onion-like, and mushroom-like odors [39]. In this study, phenethyl alcohol was present at all fermentation stages as aromatic alcohol, which had a pleasant floral aroma. 4-Terpene alcohols are warm peppery, lighter earthy, and aged woods. With respect to the acids, the contents of octanoic acid and n-Decanoic acids remained the highest over time and might provide some cheese smell. Compared with long-chain fatty acids (Octanoic acid, n-Decanoic acid and Hexanoic acid), short-chain fatty acids such as isovaleric acid had lower thresholds due to their sensory attributes [43; 44]. Esters are produced by the reaction of alcohols and carboxylic acids (or acyl-CoA) or by microbial esterase activity [45]. Long-chain acids can form long-chain esters, and long-chain esters have a slightly fatty odor. In contrast, short-chain esters have a fruity flavor [23; 46], especially methyl-branched short-chain esters, which have a positive correlation with aged meat flavors [47; 48]. In this study, the types and contents of esters gradually increased with the increase in time, and the type of esters were the maximum on the day 28. Their composition seemed to explain the aroma components of fermented pork loin ham. Ethyl octanoate was the most abundant compound during all periods, and the content of ethyl octanoate gradually decreased from day 7. Esters of production depending on the presence of ethanol and different acids as well as on the esterase/lipase activities of the strains [49]. Ethyl caprylate has been reported to bind to myofibrillar proteins, thereby altering the flavor of meat [50].