## 3 Results and Discussion
### Microbial Diversity Analysis  
#### 3.8.1 Bacterial Diversity Analysis  
The single molecule real-time sequencing was utilised to analyse normal Xuanwei hams and spoiled Xuanwei hams at the bacterial genus and species levels, as well as to study the bacterial microbial community structure of Xuanwei hams with different quality grades and muscle types (Figure 3). At the genus level (Figure 3A), 142 bacterial genus were identified, with the top 20 dominant bacterial genus being _Staphylococcus_, _Ralstonia_, _Chromolabolacter_, _Sphingomonas_, _Bacillus_, _Pseudomonas_, _Kushneria_, _Saltimicrobium_, _Tetragenococcus_, _Halomonas_, _Cithiacterium_, _Acinetobacter_, _Macroccocus_, _Halopinatiens_, _Cobetic_, _Moraxella_, _Psychrobacter_, _Bradyrhizobium_ and _Lactococcus_. In normal Xuanwei ham, _Staphylococcus_ was the most abundant genus in both BF and SM, similar to Parma ham [11], followed by _Ralstonia_ (13%) in the BF and _Chromolabolacter_ (26%) in the SM. In contrast, _Bacillus_ (39-41%) was the dominant genus in both BF and SM in spoiled hams, indicating a significant difference in the microbial community structure between normal and spoiled ham. It is worth mentioning that more _Lactococcus_ were found in spoiled hams compared to normal hams (\(p<0.05\)), consistent with a previous study by [PERSON] et al. [21]. At the species level, the number of shared and unique OTUs between different samples was analysed, and a Venn diagram was plotted based on the results of OTU cluster analysis (Figure 3B). A total of 174 bacterial species were identified, with six species found in both the SM and BF of normal and spoiled hams. The clustered heat map at the species level (Figure 3C) revealed a significant difference between normal and spoiled hams, with _Staphylococcus_ _equorum_ being the dominant bacterial species in normal hams and differing significantly \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Volatile Compounds** & **OTV** & \multicolumn{2}{c}{**Normal Ham**} & \multicolumn{2}{c}{**Spoiled Ham**} \\ \cline{3-6}  & **(ug/kg)** & **BF** & **SM** & **BF** & **SM** \\ \hline
1 & Trimethylamine & 0.032 & 0 & 0 & 159.06 & 407.81 \\
2 & Methanethiol & 0.07 & 0 & 0 & 183.61 & 85.57 \\
3 & Methyl 2-methyl butyrate & 1 & 2.08 & 2.76 & 8.65 & 3.48 \\
4 & 3-Methyl butanal & 0.1 & 266.64 & 184.59 & 123.2 & 131.6 \\
5 & Methyl isobutyrate & 1.9 & 0 & 0 & 1.9 & 0 \\
6 & 2-Pentanone & 28 & 1.77 & 0 & 0 & 0 \\
7 & Methyl butyrate & 7.1 & 0 & 0 & 2.07 & 0 \\
8 & Methyl isovalerate & 2.2 & 3.16 & 2.08 & 6.58 & 0 \\
9 & Ethyl butyrate & 0.04 & 0 & 0 & 175.6 & 0 \\
10 & Ethyl isovalerate & 3 & 2.33 & 0 & 2.03 & 3.6 \\
11 & Hexanal & 0.28 & 290.5 & 80.93 & 737.36 & 488.28 \\
12 & Methyl pentanoate & 2.2 & 1.34 & 0 & 9.02 & 0 \\
13 & Ethyl pentanoate & 0.11 & 0 & 0 & 65.82 & 0 \\
14 & Heptanal & 3 & 4.6 & 2.73 & 14.43 & 12.08 \\
15 & Methyl caroten & 10 & 0 & 0 & 1.26 & 0 \\
16 & Octanal & 0.7 & 29.44 & 21.93 & 85.03 & 75.03 \\
17 & Carbon disulphide & 0.34 & 87.15 & 8.03 & 5.53 & 14.92 \\
18 & 3-(Methylthio)propionaldehyde & 0.63 & 11.59 & 3.53 & 0 & 0 \\
19 & 3-Octenol & 2 & 15.91 & 4.35 & 18.2 & 14.76 \\
20 & Heptanol & 4.8 & 1.35 & 1.57 & 1.49 & 1.45 \\
21 & Acetic acid & 6 & 0 & 0 & 0 & 1.09 \\
22 & Decanal & 0.4 & 5.93 & 4.58 & 0 & 4.8 \\
23 & Octanol & 2.7 & 2.52 & 1.56 & 7.33 & 6.86 \\
24 & Valeric acid & 0.037 & 0 & 0 & 412.97 & 194.86 \\
25 & Hexanoic acid & 0.6 & 6.87 & 7.07 & 156.13 & 110.88 \\
26 & Phenol & 5.6 & 1.23 & 0 & 0 & 0 \\ \hline \hline \end{tabular} Odour threshold value (OTV) and odour threshold value (OAV) represented odour threshold value and odour active value, respectively. SM: Semimembranosus; BF: Biceps femoris.  
\end{table} 
Table 4: Key volatile compounds of different muscles in normal and spoiled hams (OAV \(>\) 1). from spoiled hams. This finding is consistent with a previous study by [PERSON] et al. [24] on normal Spanish dry-cured hams.