## 3 Results and Discussion
### Carboxylic Acids  
Organic acid analysis was carried out for kefir-fermented coconut water to determine changes in the concentration of malic acid, lactic acid, acetic acid, pyruvic acid, and succini  
Figure 1: The estimation of residual glucose (**A**), residual sucrose (**B**), pH (**C**), and TTA (**D**) for the different treatments of CWK fermented at 30 \({}^{\circ}\)C with 5% CO\({}_{2}\) concentration. All of the values for each experimental set represent the mean of triplicate readings. A, B, C, D, E = Different letters within the same row (different fermentation times—0 h, 24 h, 48 h, 72 h and 96 h for the same set treatment) differ significantly using [PERSON]’s least significant difference (\(p<0.05\)). a, b, c, d, e, f, g, h—Different letters within the same column (different treatments for the same time interval) differ significantly using [PERSON]’s least significant difference (\(p<0.05\)). acid. Principal component analysis (PCA) was carried out to assess the variation in these acids for all experimental sets containing different concentrations of glucose and sucrose during the fermentation that took place over 96 h. Samples were taken at 0, 24, 48, 72, and 96 h.  
The PCA- 2D score plots (Figure 2A) distinguished the CWK sets after longer fermentation times (24 h to 96 h) that were associated with higher concentrations of carboxylic acids from the non-fermented sample (0 h). PC1 and PC2 accounted for 75.2% and 12.3% of the total variation, respectively. The scores for the different kefir fermented coconut water were clearly separated according to fermentation time (T = 0, 24, 48, 72 and 96 h) indicating distinct changes in acids during fermentation. Samples at time T = 0 had negative scores along PC1. With increasing fermentation time (T = 24, 48, 72, and 96 h), sample scores became increasingly positive. Figure 2: _Cont._  
The PCA biplot shown in Figure 2B shows the scores for all the CWK sets fermented at 0, 24, 48, 72, and 96 h. The control, (T = 0 h) had high negative scores that corresponded to high negative loadings for malic acid. This finding was supported by ANOVA results shown in Supplementary Table S1-E. The malic acid concentration was significantly high for Set 3, while Set 9 had significantly low levels of malic acid (\(p\) < 0.05). The fact that malic acid was only found at the start time of fermentation (T = 0 h) indicated that malotactic fermentation occurred during CWK fermentation. Malic acid can be converted to lactic acid [51, 52] during fermentation. With increasing fermentation time, most of the sets fermented for 24, 48, and 72 h had significantly high positive scores, which corresponded to the high positive loadings of lactic acid, pyruvate acid, and succinidic acid. This finding was supported by the ANOVA results shown in Supplementary Table S1-A,C,D, which showed significantly higher concentrations of lactic acid, pyruvate acid, and succinidic acid in fermented samples with increasing fermentation time. The successful conversion of malic acid to lactic acid  
Figure 2: (**A**) PCA score plots of PC1 and PC2 for the carboxylic acids present in the different sets of CWK with different fermentation times (T = 0, 24, 48, 72 and 96 h). The samples are colour-coded as below: Legends. T= 0 h; T= 24 h; T= 48 h; T= 72 h; T= 96 h. (**B**) Principal components analysis (PCA) biplot showing PC scores for the experimental sets fermented at different times (T = 0 in red, 24 in green, 48 in blue, 72 in cyan, and 96 h in purple) that are presented as numbers and loadings of carboxylic acids in the CWK sets. The product loadings (1–150) are representative of samples and replicates. PC1 and PC2 explained 75.2% and 12.3% variances in the data, respectively. using _L. casei_ and _Lactococcus eros_, known as malolactic fermentation, has been reported in wine [53; 54]. Lactic acid has also been produced in fermented food and beverages, such as kimchi and wine, which involve both lactic acid bacteria and yeast [55; 56; 57].