## 3 Results
### MLF Assay and Basic Chemical Parameters  
#### 3.4.1 MLF Assay of Cabernet Sauvignon Wines  
Malic acid conversion rate is an important index to evaluate the MLF ability of MLB. L-malic acid was monitored during MLF in cabernet Sauvignon wines (Figure 8a). During the MLF process, the L-malic acid concentration fell dramatically with time. Following eight days of inoculation, the L-malic acid concentration in wines fermented by five strains reduced to around 1.4-1.5 g/L. On the 12 th day, the L-malic acid concentration in wines \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strains** & **Stresses** & \multicolumn{2}{c}{**Levels**} & \multicolumn{1}{c}{**R**} \\  & & **1** & **2** & **3** & \\ \hline A7 & Ethanol & \(\delta_{\rm A1}=9.80\) & \(\delta_{\rm A2}=-3.13\) & \(\delta_{\rm A3}=-6.67\) & 16.47 \\  & pH & \(\delta_{\rm B1}=1.06\) & \(\delta_{\rm B2}=-2.52\) & \(\delta_{\rm B3}=1.47\) & 3.99 \\  & SO\({}_{2}\) & \(\delta_{\rm C1}=1.30\) & \(\delta_{\rm C2}=1.23\) & \(\delta_{\rm C3}=-2.53\) & 3.83 \\ A18 & Ethanol & \(\delta_{\rm A1}=10.73\) & \(\delta_{\rm A2}=-4.21\) & \(\delta_{\rm A3}=-6.51\) & 17.24 \\  & pH & \(\delta_{\rm B1}=-1.37\) & \(\delta_{\rm B2}=0.82\) & \(\delta_{\rm B3}=0.56\) & 2.19 \\  & SO\({}_{2}\) & \(\delta_{\rm C1}=-0.76\) & \(\delta_{\rm C2}=3.06\) & \(\delta_{\rm C3}=-2.27\) & 5.33 \\ A23 & Ethanol & \(\delta_{\rm A1}=7.75\) & \(\delta_{\rm A2}=-0.91\) & \(\delta_{\rm A3}=-6.83\) & 14.58 \\  & pH & \(\delta_{\rm B1}=-2.98\) & \(\delta_{\rm B2}=1.14\) & \(\delta_{\rm B3}=1.85\) & 4.83 \\  & SO\({}_{2}\) & \(\delta_{\rm C1}=-3.00\) & \(\delta_{\rm C2}=7.10\) & \(\delta_{\rm C3}=-4.10\) & 11.20 \\ A50 & Ethanol & \(\delta_{\rm A1}=8.72\) & \(\delta_{\rm A2}=-3.14\) & \(\delta_{\rm A3}=-5.59\) & 14.31 \\  & pH & \(\delta_{\rm B1}=-0.17\) & \(\delta_{\rm B2}=0.58\) & \(\delta_{\rm B3}=-0.42\) & 1.00 \\  & SO\({}_{2}\) & \(\delta_{\rm C1}=-0.43\) & \(\delta_{\rm C2}=3.27\) & \(\delta_{\rm C3}=-2.84\) & 6.11 \\ B28 & Ethanol & \(\delta_{\rm A1}=13.16\) & \(\delta_{\rm A2}=-4.09\) & \(\delta_{\rm A3}=-9.07\) & 22.23 \\  & pH & \(\delta_{\rm B1}=0.18\) & \(\delta_{\rm B2}=-1.22\) & \(\delta_{\rm B3}=1.04\) & 2.26 \\  & SO\({}_{2}\) & \(\delta_{\rm C1}=0.44\) & \(\delta_{\rm C2}=3.77\) & \(\delta_{\rm C3}=-4.20\) & 7.97 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The orthogonal experiment results. Figure 7: \(\beta\)-D-glucosidase activity of A7, A18, A23, A50, B28, and control strains. Different small letters indicate significant differences according to the LSD Fisher test (\(p<0.05\)). fermented with A7, A50, and B28 fell to around 0.6 g/L. Simultaneously, the L-malic acid concentration in wines fermented by _O. oeni_ 31-DH and _L. plantarum_ BV-S2 fell to around 0.3-0.47 g/L. After 24 days, _O. oeni_ 31-DH L-malic acid decreased to less than 0.1 g/L. _O. oeni_ 31-DH finished the MLF first. Secondly, on the 28 th day, _L. plantarum_ BV-S2 finished fermentation. The L-malic acid of A7, A50, and B28 also decreased continuously, and the L-malic acid of A7 decreased to 0.15 g/L on the 32 nd day, which showed good fermentation ability. The L-malic acid of A50 and B28 decreased to about 0.4 g/L on the 28 th day and remained unchanged, indicating that the strains also had a specific acid-reducing ability. A7, A50, B28, and the controls were inoculated at about 10\({}^{7}\) CFU/mL. The cell in the wines during MLF was detected (Figure 8b). After the inoculation, the cell of the strains showed a downward trend. Moreover, the downward trend was the same. Perhaps the wine environment inhibited the growth of strains. When strains adapted to the environment, the number of strains gradually stabilized. On the eighth day, the viable cell counts began to increase. After the 12 th day, the viable cell counts of A7, A50, and B28 began to decline gradually. After 20 days of inoculation, the viable cell counts of _O. oeni_ 31-DH and _L. plantarum_ BV-S2 began to increase. Then the viable cell counts began to decrease from the 28 th day.