## 3 Results and Discussion
### Response Profile of E-Nose for Unfermented Specimens  
#### 3.2.1 Radar Plot of Unfermented Specimens  
E-nose makes remarkable contributions to the mode recognition analyses of odors, providing a non-destructive, comprehensive, and quick replacement to evaluate food quality [26; 34]. In this study, 10 sensors were utilized for the aroma assay to evaluate the response of volatile substances in four groups of unfermented specimens. The radar chart manifested the response values of four groups of unfermented specimens on the sensory array of the E-nose. The response value of the four groups of unfermented specimens on 10 sensors is shown in Figure 2. The E-nose exhibited fine ability in identifying four groups of unfermented specimens mainly via W2S and W3S sensors (Figure 2). W2S (sensitive to alcohol and aldehyde substances) and W3S (sensitive to alkane substances) sensors bestowed stronger and diverse responses to odorant substances of the four groups of unfermented specimens, suggesting that the unfermented specimens may possess higher abundances of alcohol, aldehyde, ketone, and aliphatic substances. Simultaneously, the W3C (sensitive to ammonia substances) sensor exhibited lower signal strength in the specimens, indicating that it was insensitive to the variations in aroma substances of unfermented specimens. The response values of specimen CPBY-0 h in W5C (sensitive to phenyl substances) and W3S sensors were stronger than those of the other three specimens, indicating that CPBY-0 h may possess higher abundances of alkanes and aliphatic substances. The response values of specimen CP-0 h in W1S (sensitive to methane substances) and W2S sensors were stronger than those of the other three specimens, suggesting that CP-0 h may possess higher abundances of alcohols and aldehydes. The other five sensors were less sensitive to the four groups of unfermented specimens, and the response values were closer, indicating that the volatile substances identified were similar and the signal intensities showed no obvious difference among unfermented specimens. It was difficult to distinguish the four \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Samples** & & & & & & & & \\ \hline
**Amino Acid (mg/kg)** & & & & & & & & \\ \hline Aspartate (Asp) & 0.76 & 1.19 & 2.45 & 2.84 & 0.09 & 0.12 & 1.45 & 1.39 \\ Threonine (Thr) & 0.65 & 0.80 & 3.52 & 4.06 & 0.50 & 0.65 & 0.92 & 0.96 \\ Serine (Ser) & 0.19 & 0.52 & 8.03 & 9.85 & 0.12 & 0.18 & 5.65 & 6.78 \\ Glutamic acid (Glu) & 4.30 & 5.41 & 5.60 & 6.44 & 1.18 & 1.29 & 1.41 & 1.85 \\ Glycine (Gly) & 0.27 & 0.34 & 1.66 & 2.01 & 0.05 & 0.16 & 0.84 & 1.03 \\ Alanine (Ala) & 0.41 & 0.79 & 7.63 & 7.95 & 0.18 & 0.22 & 4.90 & 5.58 \\ Cysteine (Cys) & 0.04 & 0.07 & 0.40 & 0.92 & 0.03 & 0.16 & 0.14 & 0.12 \\ Valine (Val) & 16.23 & 16.54 & 16.69 & 17.35 & 6.51 & 6.85 & 8.16 & 9.64 \\ Methionine (Met) & 0.03 & 0.07 & 0.04 & 0.18 & 0.02 & 0.08 & 0.31 & 0.27 \\ Isolecucine (Ile) & 0.17 & 0.39 & 0.51 & 0.90 & 0.11 & 0.17 & 0.12 & 0.14 \\ Leucine (Leu) & 0.09 & 0.16 & 0.22 & 0.62 & 0.02 & 0.03 & 0.24 & 0.58 \\ Tyrosine (Tyr) & 0.24 & 0.31 & 0.15 & 0.34 & 0.05 & 0.12 & 0.13 & 0.21 \\ Phenylalanine (Phe) & 0.28 & 0.42 & 0.45 & 0.67 & 0.12 & 0.29 & 0.37 & 0.67 \\ Histidine (His) & 0.71 & 1.06 & 1.84 & 1.90 & 0.36 & 0.49 & 1.09 & 1.32 \\ Lysine (Lys) & 2.93 & 3.14 & 2.35 & 4.02 & 1.16 & 1.35 & 0.86 & 0.85 \\ Arginine (Arg) & 15.47 & 16.01 & 16.12 & 17.89 & 7.53 & 8.27 & 11.85 & 12.19 \\ Proline (Pro) & 0.31 & 0.64 & 0.98 & 1.23 & 0.32 & 0.46 & 0.23 & 0.92 \\ Total & 43.08 & 47.86 & 68.64 & 79.17 & 18.35 & 20.89 & 38.67 & 44.50 \\ \hline \hline \end{tabular} Note: Group CP-0 h, unfermented chicken milk; Group CPBY-0 h, unfermented chicken milk with yam addition; Group CPBY-0 h, unfermented chicken milk with pgain treatment; Group CP-12 h, fermented chicken milk with pgain treatment; Group CPY-12 h, fermented chicken milk with yam addition; Group CPBY-12 h, fermented chicken milk with pgain treatment plus yam addition.  
\end{table}