## 3 Results and Discussion
### Effect of Lactic-Acetic Acid Co-Fermentation on Phenolics of Bicultured Jujube Pures  
In the unfermented samples, the primary phenolic compounds--namely chlorogenic acid, sinapic acid, quercetin, catechin, and peonidin-3,5-diglucoside--were quantified at approximately 1.29 mg/100 g, 0.85 mg/100 g, 1.29 mg/100 g, 1.60 mg/100 g, and 25.19 mg/100 g, respectively. Following the fermentation treatment, a remarkable and statistically significant (\(p<0.05\)) augmentation in the concentrations of key phenolic compounds was observed in the bicultured pures, specifically sinapic acid, ferulic acid, and rutin, reaching 243%, 210%, and 239% of their respective initial values on average. Notably, phenolic compounds such as ferulic acid are reported to undergo reduction, resulting in the formation of dihydroferulic acid. Despite the presence of decarboxylases and reductases in LAB strains, exemplified by _Lactiplantiobacillus plantarum_ GK3 and _Lactobacillus acidophilus_ 85 [17; 18; 38], the observed increase in ferulic acids in the bicultured pures contradicts this phenomenon. This apparent contradiction supports the hypothesis that lactic-acetic acid co-fermentation can enhance specific phenolic compounds, such as ferulic acid. Lactic acid bacteria (LAB) are known to enzymatically catalyze the cleavage and subsequent acidification of glycosides and esters conjugated with phenolic compounds. Also, acetic acid \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Amino Acids**} & \multicolumn{4}{c}{**JP (mg/100 g)**} \\ \cline{2-5}  & **JLcAp** & **JLhAp** & **JLpAp** & **JCON** \\ \hline L-Aspartic acid & 23.35 \(\pm\) 0.05 d & 26.45 \(\pm\) 0.11 c & 27.46 \(\pm\) 0.11 a & 27.10 \(\pm\) 0.10 b \\ L-Threonine & 2.00 \(\pm\) 0.05 b & 2.41 \(\pm\) 0.05 a & 1.93 \(\pm\) 0.05 b & 2.30 \(\pm\) 0.10 a \\ L-Serine & 2.85 \(\pm\) 0.11 b & 3.47 \(\pm\) 0.00 a & 3.03 \(\pm\) 0.09 b & 3.30 \(\pm\) 0.10 a \\ L-Glutamic acid & 7.57 \(\pm\) 0.05 c & 8.76 \(\pm\) 0.11 a & 8.37 \(\pm\) 0.14 b & 6.93 \(\pm\) 0.06 d \\ L-Glycine & 2.03 \(\pm\) 0.05 c & 2.57 \(\pm\) 0.11 b & 2.09 \(\pm\) 0.09 c & 3.20 \(\pm\) 0.10 a \\ L-Alanine & 3.82 \(\pm\) 0.05 c & 4.23 \(\pm\) 0.09 a & 4.01 \(\pm\) 0.14 b & 4.40 \(\pm\) 0.10 a \\ L-Valine & 2.60 \(\pm\) 0.11 b & 4.82 \(\pm\) 0.11 a & 1.99 \(\pm\) 0.09 c & 2.83 \(\pm\) 0.06 b \\ L-Methionine & nd & nd & 0.85 \(\pm\) 0.09 a & \\ L-Isoleucine & 1.41 \(\pm\) 0.19 c & 1.84 \(\pm\) 0.07 b & 1.23 \(\pm\) 0.09 c & 3.70 \(\pm\) 0.10 a \\ L-Leucine & 2.32 \(\pm\) 0.05 b & 2.82 \(\pm\) 0.00 a & 2.15 \(\pm\) 0.05 c & 2.93 \(\pm\) 0.06 a \\ L-Tyrosine & 1.00 \(\pm\) 0.05 a & 1.15 \(\pm\) 0.10 a & 0.85 \(\pm\) 0.01 b & 0.83 \(\pm\) 0.06 b \\ L-Phenylalanine & 2.57 \(\pm\) 0.11 a & 2.66 \(\pm\) 0.05 a & 0.76 \(\pm\) 0.00 c & 1.17 \(\pm\) 0.06 b \\ L-Histidine & 5.51 \(\pm\) 0.05 c & 6.23 \(\pm\) 0.11 a & 6.00 \(\pm\) 0.14 a & 5.93 \(\pm\) 0.06 b \\ L-Lysine & 2.75 \(\pm\) 0.05 c & 5.10 \(\pm\) 0.05 a & 2.91 \(\pm\) 0.05 b & 5.17 \(\pm\) 0.06 a \\ L-Arginine & 2.19 \(\pm\) 0.05 c & 2.82 \(\pm\) 0.09 a & 2.59 \(\pm\) 0.05 b & 2.53 \(\pm\) 0.06 b \\ L-Proline & 77.65 \(\pm\) 0.09 d & 81.85 \(\pm\) 0.05 c & 86.89 \(\pm\) 0.55 b & 111.70 \(\pm\) 0.10 a \\
**Total free amino** & **139.62 \(\pm\) 1.15 d** & **157.17 \(\pm\) 1.12 b** & **153.11 \(\pm\) 1.80 c** & **184.03 \(\pm\) 1.16 a** \\ \hline \hline \end{tabular} Data expressed as mean \(\pm\) standard deviation. Means in the same row with different superscript letters are significantly different (\(p<0.05\)). **Note:** n.d—not detected. JLcAp—_Lactobacillus casei_ Lc 122—_Acteobacter pasteurium_ Ap-As.1.41 HuNiang 1.01 puree; JLhAp—_Lactobacillus helveturus_ Lh 43—_A. pasteurium_ Ap-As.1.41 HuNiang 1.01 puree; JLpAp—_Lactiplantiobacillus plantarum—_A. pasteurium_ Ap-As.1.41 HuNiang 1.01 puree; JLpAp—_Lactiplantiobacillus plantarum—_A. pasteurium_ Ap-As.1.41 HuNiang 1.01 puree; JCON—puree with no bacteria inoculants (unfermented).  
\end{table} 
Table 2: Free amino acid content in bicultured Junzao jujuube purees.