## 3 Results and Discussion
### Volatile Flavor Compound Analysis  
In this study, a total of 66 volatile flavor compounds were identified with significant differences between the groups, and the cluster analysis results are shown in Figure 1. These compounds include 22 alcohols, 11 ketones, 7 esters, 5 aldehydes, 5 acids, and 16 other compounds. The HS group exhibited the highest total concentration of volatile compounds, with the highest content of acids, esters, alcohols, and aldehydes, while the RS group had the highest ketone content. The results of the cluster analysis indicated that the RS group and the FS group shared a higher degree of similarity. Reduced-salt cheese exhibits higher concentrations of volatile compounds, due to the early growth of bacteria and increased enzymatic activity [7]. The HS group exhibited significantly higher levels of acids, including acetic acid, a primary organic acid in cheddar cheese [16]. Acetic acid can be synthesized through the catabolic metabolism of lactose, citrate, and free fatty acids, or via amino acid metabolism, and is directly associated with a sour taste [17]. The highest concentration of acetic acid in the HS group may indicate that salt reduction enhances the sour taste of cheese samples. The HS group also had significantly higher levels of esters, particularly ethyl caproate and ethyl butanoate, consistent with previous research findings [7]. Ethyl acetate, known for its fruity flavor, and ethyl butanoate, with its pineapple-like aroma, are formed through the esterification of ethanol and acids or amino acid metabolism. While present at low concentrations, they play a significant role in the overall sensory experience of cheese [18]. The HS group also had notably higher levels of alcohols, including ethanol, which accounted for the highest proportion, aligning with the findings by [PERSON] et al. [19]. The HS group exhibited significantly higher levels of aldehydes, which are primarily derived from amino acid and fatty acid metabolism in cheese. Branched aldehydes and aldehydes derived from amino acids are often positively correlated with cheese flavor. For instance, hexanal, produced through \(\beta\)-oxidation of fatty acids, imparts a green flavor, while 3-methylbutanal, formed via amino acid metabolism, has a fruity aroma [20]. The RS group, in contrast, had notably higher levels of ketones, particularly 2-nonanone, which is formed through \(\beta\)-oxidation and decarboxylation of fatty acids, contributing a hot milk flavor [21]. This contrasts with the findings by [PERSON] et al. [19], who discovered fewer ketones in low-salt (1.3%) cheese. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Hardness (g)** & **Elasticity** & **Chewiness** & **Adhesiveness** \\ \hline FS & 2330.73 \(\pm\) 5.33 \({}^{\text{a}}\) & 0.96 \(\pm\) 0.03 \({}^{\text{b}}\) & 1853.79 \(\pm\) 2.26 \({}^{\text{a}}\) & 1292.38 \(\pm\) 3.07 \({}^{\text{c}}\) \\ RS & 2150.73 \(\pm\) 4.53 \({}^{\text{b}}\) & 1.01 \(\pm\) 0.02 \({}^{\text{b}}\) & 1592.71 \(\pm\) 2.43 \({}^{\text{b}}\) & 1502.38 \(\pm\) 2.03 \({}^{\text{b}}\) \\ HS & 1880.51 \(\pm\) 3.02 \({}^{\text{c}}\) & 1.17 \(\pm\) 0.04 \({}^{\text{a}}\) & 1385.52 \(\pm\) 2.39 \({}^{\text{c}}\) & 1713.16 \(\pm\) 2.99 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} \({}^{\text{Values in columns marked with different lowercase letters are significantly different ($p<0.05$)}}\).  
\end{table} 
Table 2: Texture profile analysis of cheddar cheese. This discrepancy may be attributed to differences in the pH value, water activity, and non-refmenting lactic acid bacteria, which affect the activity of cheese lipase [22]. Therefore, the reduction in salt content possibly leads to the intensification of amino acid and fatty acid metabolism, resulting in an increase in the complexity of volatile flavor compounds in cheeses. Figure 1: Cluster heatmap of differential volatile flavor compounds in three types of cheddar cheese with varying salt concentrations.