# Effect of Deacidification Treatment on the Flavor Quality of Zaosu Pear-Kiwifruit Wine
## 3 Results and Discussion
### Chemical Composition of Pear-Kiwifruit Wine
#### 3.2.2 Organic Acid Content of Pear-Kiwifruit Wine after Deacidification  
We previously identified seven organic acids in pear-kiwifruit juice and wines made from it (Figure 3A). L-Malic acid (1.97 g/L) was the most abundant organic acid in the mixed juice, followed by quinic acid (1.53 g/L) and tartaric acid (1.43 g/L), depending on the specific fruit varieties used (Supplementary Table S3). After alcoholic fermentation, the concentrations of citric, succinic, and lactic acids increased significantly (\(p<\) 0.05), whereas those of oxal, L-malic, quinic, and tartaric acids decreased (Figure 3A).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Composition** & **AF Wine a** & **MLF Wine b** & **CD Wine c** \\ \hline Total sugar (glucose, g/L) & 3.93 \(\pm\) 0.02 a & 2.34 \(\pm\) 0.04 b & 3.87 \(\pm\) 0.03 a [FOOTNOTE:a]Footnote a: All values are reported as the mean (\(\pm\)SD) of three experiments. Values in the same row with different letters indicate a statistical difference according to [PERSON]’s test (\(p<\) 0.05). a AF wine: pear-kiwifruit juice co-inoculated with _Saccharomyces cerevisiae_ ES488 and _Metschnikowiaia_. _pulcherina_ 346. b MLF wine: AF wine inoculated with _Ontococcus eeni_ strain GF-2. c CD wine: wind chemically deacidified by 1.0 g/L Na\({}_{2}\)CO\({}_{3}\), 1.0 g/L K\({}_{2}\)CO\({}_{3}\), and 5.0 g/L KHC\({}_{4}\)H\({}_{4}\)O\({}_{6}\). & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Physicochemical properties of three pear-kiwifruit wines.  
Figure 2: Response surface and contour plots for total conversion of L-malic acid in pear–kiwifruit wine as a function of the independent variables: (**A**) effect of the initial pH and malolactic fermentation temperature; (**B**) effect of the initial pH and inoculation amount; (**C**) effect of the malolactic fermentation temperature and inoculation amount.  
As expected, MLF with _O. oeni_ GF-2 greatly reduced L-malic acid (by 97.6%) and correspondingly increased the concentration of lactic acid from 0.64 to 1.23 g/L (Figure 3A), i.e., this strain had excellent fermentation performance in pear-kiwifruit wine. It appeared that the malolactic enzyme (MLE) produced by _O. oeni_ GF-2 had a strong affinity for L-malic acid. The total organic acid content in MLF wine was 29.7% lower than that in untreated wine, mainly resulting from significant reductions in succinic and tartaric acid, in addition to that of L-malic acid (Supplementary Table S3). Unlike succinic acid, tartaric acid is not usually converted by _O. oeni_, but precipitates as potassium hydrogen tartrate [26]. MLF also reduced the concentration of astringent quinic acid by up to 0.2 g/L, indicating that _O. oeni_ GF-2 could balance the wine taste by alleviating excessive astringency, as well as sourness.  
The chemical deacidification with 1.0 g/L Na\({}_{2}\)CO\({}_{3}\), 1.0 g/L K\({}_{2}\)CO\({}_{3}\), and 5.0 g/L KHC\({}_{4}\)H\({}_{4}\)O\({}_{6}\) significantly reduced the concentrations of all detected organic acids (_p_ < 0.05), except L-malic acid, and lactic acid completely disappeared (Figure 3A). Chemically deacidified wine had a lower total concentration (4.35 g/L) of organic acids than MLF wine, because of a marked decrease in lactic, oxalic, and tartaric acids.