## 3 Results
### Characterization of Extracted Proteins from DB-Yeast and Se-Enriched DB-Yeast  
The pH of the solution treated with HCl, and the reducing power, hydroxyl radical removal capacity, and total sulfhydryl and secondary structure composition treated with different volumes of H\({}_{2}\)O\({}_{2}\) of extracted proteins from DB-yeast and Se-enriched DB-yeast were evaluated to better understand the excellent characteristics of Se-enriched DB-yeast. The pH of the Se-enriched DB-yeast extracted protein solution (from 10.00 \(\pm\) 0.06 to 5.25 \(\pm\) 0.07) decreased more slowly than that of the DB-yeast extracted protein solution (from 10.02 \(\pm\) 0.04 to 2.23 \(\pm\) 0.07) following the addition of HCl (Figure 5A). The reducing power of the Se-enriched DB-yeast extracted protein (1.65 \(\pm\) 0.08) was significantly higher than that of the DB-yeast extracted protein (1.20 \(\pm\) 0.07) (\(p\)-value = 0.002) (Figure 5B). The hydroxyl radical removal capacity of the Se-enriched DB-yeast extracted protein (53.34 \(\pm\) 4.56%) was significantly higher than that of the DB-yeast extracted protein (81.61 \(\pm\) 5.62%) (\(p\)-value = 0.002) (Figure 5C). The sulfhydryl content of the Se-enriched DB-yeast extracted protein (from 37.5 \(\pm\) 0.7 \(\mu\)mol/L to 28.7 \(\pm\) 0.9 \(\mu\)mol/L) decreased more slowly than that of the DB-yeast extracted protein (from 38.2 \(\pm\) 1.1 \(\mu\)mol/L to 25.9 \(\pm\)0.8 \(\mu\)mol/L) as the H\({}_{2}\)O\({}_{2}\) concentration increased (from 0 to 16 mmol/L) (Figure 5D). As shown in Table 2, after treatment with H\({}_{2}\)O\({}_{2}\), the \(\beta\)-sheet content decreased, whereas the \(\beta\)-turn, \(\alpha\)-helix, and random coil content increased. The \(\beta\)-sheet content of the Se-enriched DB-yeast extracted protein (from 47.55% to 43.08%) decreased more slowly than that of the DB-yeast extracted protein (from 47.12% to 40.19%) as the H\({}_{2}\)O\({}_{2}\) concentration increased (from 0 to 16 mmol/L). In addition, as the most abundant structure, \(\beta\)-sheet was more susceptible to oxidation \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Amino Acids**} & \multicolumn{2}{c}{**DB-Yeast**} & \multicolumn{2}{c}{**Se-Enriched DB-Yeast Yeast**} & \multirow{2}{*}{**Relative Ratio Difference**} \\ \cline{2-2} \cline{4-6}  & **Content a** & **Ratio b** & **Content a** & **Ratio b** & \\ \hline Total & 39.4 & - & 43.3 & - & - \\ Arg & 2.23 & 5.7\% & 3.14 & 7.3\% & 1.59\% \\ Pro & 1.36 & 3.5\% & 1.8 & 4.2\% & 0.71\% \\ Lys & 3.44 & 8.7\% & 4.07 & 9.4\% & 0.67\% \\ Gly & 2.25 & 5.7\% & 2.76 & 6.4\% & 0.66\% \\ Ser & 2.14 & 5.4\% & 2.48 & 5.7\% & 0.30\% \\ Val & 1.48 & 3.8\% & 1.69 & 3.9\% & 0.15\% \\ Tyr & 1.4 & 3.6\% & 1.59 & 3.7\% & 0.12\% \\ His & 0.95 & 2.4\% & 1.09 & 2.5\% & 0.11\% \\ Thr & 2.28 & 5.8\% & 2.54 & 5.9\% & 0.08\% \\ Leu & 3.14 & 8.0\% & 3.48 & 8.0\% & 0.07\% \\ Ala & 2.65 & 6.7\% & 2.93 & 6.8\% & 0.04\% \\ Phe & 1.88 & 4.8\% & 2.04 & 4.7\% & -0.06\% \\ Asp & 4.45 & 11.3\% & 4.86 & 11.2\% & -0.07\% \\ Met & 0.53 & 1.3\% & 0.55 & 1.3\% & -0.07\% \\ Ile & 2.14 & 5.4\% & 2.24 & 5.2\% & -0.26\% \\ Cys & 0.4 & 1.0\% & 0.29 & 0.7\% & -0.35\% \\ Glu & 6.73 & 17.1\% & 5.73 & 13.2\% & -3.85\% \\ \hline \hline \end{tabular}  
* g/100g: b ratio compared with total amino-acid content.  
\end{table} 
Table 1: Amino-acid composition of discarded beer (DB)-yeast and Se-enriched DB-yeast. and denaturation than the other structures. Therefore, Se can protect Se-enriched DB-yeast extracted protein from oxidation and denaturation.