## 2 Results
### Primary Metabolites in Korla Pear  
Primary metabolites in the pulp of Korla pear harvested in 2018 were analyzed by using GC-MS (Table 2). As a result, seven amino acids, four organic acids, two fatty acids and seven sugars were detected (Table S6). In addition to the high content of malic acid and fructose, glucitol was also detected at a high level of 12.17-24.34 mg/g. Shikimic acid was undetectable. l-(+)-Tartaric acid was detected at a level of 2.36-7.79 \(\mu\)g/g, but it was rarely counted in most studies due to its low concentration. Galactose was detected at a level of 0.14-0.30 mg/g, while it was not considered in most studies owing to its low sweetness value [5; 6]. The sugar/acid ratio of Korla pear ranged from 42.06 to 74.03, which was higher than that of many other pear varieties such as Dangshan, Yali and Nanguo pear cultivars [2; 3; 5], and thus might greatly contribute to its excellent quality [3].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**F1/Not** **Satisfactory**} & \multirow{2}{*}{**F2/Fair**} & \multirow{2}{*}{**F3/Satisfactory**} & \multirow{2}{*}{**F4/Good**} & \multirow{2}{*}{**F5/Very Good**} & \multirow{2}{*}{**F6/Excellent**} & \multirow{2}{*}{**Rank**} \\ \cline{5-6}  & & & & 2019 & & & \\ S1 & 0.024 & 0.254 & 0.630 & **0.721** & 0.373 & 0.057 & 5 \\ S2 & 0.005 & 0.139 & 0.462 & **0.710** & 0.559 & 0.167 & 6 \\ S3 & 0.024 & 0.244 & 0.594 & **0.709** & 0.411 & 0.087 & 7 \\ S4 & 0.030 & 0.296 & 0.693 & **0.698** & 0.279 & 0.023 & 9 \\ S5 & 0.022 & 0.241 & 0.610 & **0.722** & 0.399 & 0.074 & 4 \\ S6 & 0.033 & 0.307 & **0.683** & 0.663 & 0.302 & 0.090 & 11 \\ S7 & 0.038 & 0.311 & **0.682** & 0.675 & 0.28 & 0.026 & 12 \\ S8 & 0.039 & 0.318 & **0.686** & 0.666 & 0.279 & 0.027 & 10 \\ S9 & 0.019 & 0.221 & 0.578 & **0.726** & 0.430 & 0.09 & 3 \\ S10 & 0.026 & 0.264 & 0.635 & **0.708** & 0.365 & 0.058 & 8 \\ S11 & 0.007 & 0.162 & 0.518 & **0.741** & 0.486 & 0.112 & 1 \\ S12 & 0.009 & 0.165 & 0.508 & **0.733** & 0.502 & 0.125 & 2 \\ \hline \hline \end{tabular} Note: bold numbers are the maximum similarity values of pear samples on the standard fuzzy scale.  
\end{table}
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Compounds**} & \multirow{2}{*}{**RT**} & \multicolumn{4}{c}{**Concentration (\(\mu\)g/g FW)**} \\ \cline{3-5}  & & **Maximum** & **Sample** & **Minimum** & **Sample** \\ \hline
**Amino acid** & & & & \\ l-Valine & 6.11 & 5.36 \(\pm\) 0.29 & S12 & 0.30 \(\pm\) 0.25 & S6 \\ l-Isoucine & 8.12 & 1.01 \(\pm\) 0.07 & S12 & - & S6 \\ l-Proline & 9.21 & 37.26 \(\pm\) 0.70 & S12 & 11.93 \(\pm\) 0.98 & S6 \\ Serine & 10.18 & 4.75 \(\pm\) 0.21 & S12 & 0.05 \(\pm\) 0.07 & S5 \\ l-Threonine & 11.00 & 2.81 \(\pm\) 0.03 & S12 & 0.02 \(\pm\) 0.00 & S3 \\ l-Aspartz acid & 15.67 & 52.88 \(\pm\) 5.89 & S12 & 1.32 \(\pm\) 0.70 & S5 \\ l-Glutamic acid & 19.24 & 4.73 \(\pm\) 0.10 & S12 & 0.09 \(\pm\) 0.05 & S6 \\
**Organic acids** & & & & \\ Malic acid & 14.61 & 1809.13 \(\pm\) 420.52 & S8 & 600.20 \(\pm\) 25.76 & S9 \\ l-(+)-Tartaric acid & 18.51 & 7.79 \(\pm\) 1.81 & S8 & 2.36 \(\pm\) 0.24 & S2 \\ Citric acid & 26.21 & 31.40 \(\pm\) 2.27 & S11 & 12.35 \(\pm\) 1.10 & S9 \\ Quininic acid & 27.46 & 212.43 \(\pm\) 162.28 & S10 & 105.39 \(\pm\) 20.03 & S11 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Primary metabolites detected in the pulp of Korla pear fruit by using GC-MS.