## 3 Results and Discussion
### Taste Characteristics of Sausage Model  
Electronic tongue technology was used to further examine the impact of corn starch and soy protein isolates on the flavor characteristics of a fermented sausage model. The electronic tongue simulates the human tongue's ability to perceive key taste attributes, such as sourness, sweetness, saltiness, bitterness, and umami, offering an objective reflection of taste differences between samples. As shown in Figure 5A, the FCC group (corn starch) exhibited significantly increased sourness and decreased saltiness, which can be attributed to the accumulation of organic acids produced by an active glycolysis pathway and the lower degree of fat hydrolysis. The FNP group (soy protein isolates) exhibited a prominent umami response, attributable to its high content of glutamic acid and flavor peptides, which synergistically interact with ester compounds to enhance the overall flavor. As shown in Figure 5B, a principal component analysis (PCA) explained 87.46% of the total variance, effectively distinguishing the taste distribution characteristics among the different treatment groups. PC1 (71.80%) primarily differentiates between carbon source and nitrogen source treatments, while PC2 (15.66%) reflects differences in fermentation levels. The FNP and FCC groups were positioned on either side of the control group in the PCA space, suggesting that carbon and nitrogen sources may induce distinct taste clustering patterns through different metabolic regulation mechanisms. When combined with analyses of FAAs, free fatty acids, and volatile flavors, it can be inferred that the enhanced sourness in the FCC group was related to the acidic byproducts from active sugar metabolism, while the decreased saltiness was likely due to lower fat hydrolysis and limited salt-soluble protein degradation. An electronic tongue analysis indicated enhanced umami and taste richness in the FNP group, which may be associated with the accumulation of short peptides and FAAs, as well as abundant esters, pyrazines, and furans.  
Figure 5: Taste characteristics of fermented sausage model, including bar chart of the electronic tongue (**A**), PCA plot of the electronic tongue (**B**), and correlation heatmap with major amino acids, fatty acids, and volatile compounds (**C**). Red indicates a positive correlation, blue indicates a negative correlation, and white indicates no correlation. Different letters under the same parameter indicate significant differences (\(p<0.05\)); asterisks indicate significance levels: \({}^{*}p<0.05\), \({}^{**}p<0.01\).  
To further explore the relationship between flavor compounds and sensory taste attributes, a Spearman correlation analysis was performed to construct a correlation heatmap between 44 major volatile and non-volatile flavor compounds and 8 electronic tongue sensory characteristics (Figure 5C). The results showed that compounds such as isoamyl alcohol, 3-hydroxy-2-butanone, isobutyric acid, and ethyl isoamyl ester were positively correlated with umami, richness, and saltiness, suggesting their role in enhancing these taste attributes. Phenylethylanol, 2-heptanone, and the umami amino acid glutamic acid also significantly contributed to the umami characteristic. Additionally, while free fatty acids enhance saltiness, they may also impart bitterness and a bitter aftertaste. Compounds such as 1-octen-3-one, hexanal, and octanal were positively correlated with astringency, bitterness, and sourness, indicating that these compounds could contribute to unpleasant sensory experiences at high concentrations.  
In summary, the analysis of both the electronic tongue data and flavor compounds revealed a significant association between key metabolites and taste attributes. The FCC group exhibited a fresh, acidic taste with reduced saltiness, while the FNP group exhibited prominent umami and richness.