## Results
### The Assessment of Taste of Flat Peaches from Xinjiang
#### 3.1.2 The Composition and Content of Soluble Sugars and Organic Acids of Flat Peaches from Xinjiang
The ratio of malic acid, quintic acid, citric acid, and succinic acid was approximately 2:2:1:1, which might be one of the reasons for the characteristic acidity of the taste of flat peaches. Similar to the effect of sugar on the sweetness of flat peaches, differences in the acidity of flat peaches were influenced not only by the absolute content of organic acids but also by the proportion of organic acids. In conclusion, the distribution and proportion of the content of sugars and organic acid compounds seemed to play a crucial role in influencing the sweetness and acidity of the flat peaches. Assessment of Phenolic Compounds and Antioxidant Capacity of Flat Peaches from Xinjiang 3.2.1. Analysis of Phenolic Compounds, TFC, and TPC in Flat Peaches from Xinjiang  
Numerous studies have shown that phenolic compounds, as secondary metabolites of plants, are major contributors to antioxidant capacity [65]. Nine phenolic compounds have been identified in flat peaches (Qingpan, QP; Ruipan 2, R2; Ruipan 4, R4; Wanpan, WP) with HPLC (Table 1). Chlorogenic acid (0.22-32.29%) was the most abundant phenolic compound of the flat peaches from Xinjiang, with its content ranging from 1.58 to 29.49 mg/100 g FW (Supplementary Figure S2). Among them, R4 (29.49 mg/100 g FW) had the highest content of chlorogenic acid, about 20 times more than the other flat peaches. Proanthocyanidin B1 (0.82-19.92%) was the second most abundant phenolic compound of the flat peaches from Xinjiang, with concentrations ranging from 0.75 to 18.18 mg/100 g FW. In addition to the above, neochlorogenic acid and catechin were abundant in the flat peaches, ranging from 0.17 to 7.36 mg/100 g FW and 0.40 to 13.11 mg/100 g FW, accounting for 0.19-8.06% and 0.44-14.36% of the total phenolic compounds, respectively. The lower content of catechins compared to chlorogenic acid and neochlorogenic acid may be due to the fact that catechins are more easily oxidized, resulting in their reduced content [66]. The amounts of the remaining five phenolic compounds identified were relatively small in the tested flat peaches. Earlier studies have pointed out that the most important acid in peaches is chlorogenic acid, which has a high antioxidant capacity [67]. As one kind of polyphenolic compound, flavonoids are also of great significance to human health. As shown in Figure 2b, TFC ranged from 11.30 to 289.02 mg RE/100 g and TPC ranged from 15.07 to 182.80 mg GAE/100 g in the flat peaches, which was also consis \begin{table}
\begin{tabular}{c c c c c} \hline
**Variety** & **QP** & **R2** & **R4** & **WP** \\ \hline Coumaric acid & 0.19 \(\pm\) 0.01 b & 0.39 \(\pm\) 0.03 a & 0.43 \(\pm\) 0.03 a & 0.13 \(\pm\) 0.01 c \\ Proanthocyanidin B1 & 2.77 \(\pm\) 0.22 b & 2.05 \(\pm\) 0.16 c & 18.19 \(\pm\) 0.54 a & 0.75 \(\pm\) 0.05 d \\ Neochlorogenic acid & 1.12 \(\pm\) 0.06 c & 1.81 \(\pm\) 0.07 b & 7.36 \(\pm\) 0.15 a & 0.17 \(\pm\) 0.02 d \\ Catechin & 3.14 \(\pm\) 0.05 b & 1.46 \(\pm\) 0.04 c & 13.11 \(\pm\) 0.48 a & 0.40 \(\pm\) 0.02 d \\ Vanillic acid & 0.08 \(\pm\) 0.01 c & 0.49 \(\pm\) 0.02 a & 0.14 \(\pm\) 0.01 b & 0.08 \(\pm\) 0.01 c \\ Chlorogenic acid & 1.58 \(\pm\) 0.02 b & 1.82 \(\pm\) 0.16 b & 29.49 \(\pm\) 1.79 a & 0.20 \(\pm\) 0.02 b \\ Epicatechin & 0.13 \(\pm\) 0.01 c & 0.44 \(\pm\) 0.04 b & 1.49 \(\pm\) 0.11 a & n. d. \\ Rutin & 0.26 \(\pm\) 0.01 b & 0.12 \(\pm\) 0.02 d & 0.43 \(\pm\) 0.02 a & 0.17 \(\pm\) 0.02 c \\ Quercetin & 0.14 \(\pm\) 0.01 c & 0.49 \(\pm\) 0.01 a & 0.11 \(\pm\) 0.01 d & 0.19 \(\pm\) 0.03 b \\ \hline \end{tabular} \(\pi\) n. d. \(\pi\) indicates that the substance was not detected in the corresponding sample. Each value was the mean \(\pm\) standard deviation. Significant variations with a level of \(p\leq\) 0.05 (Duncan’s test) are shown by different letters for each sample.  
\end{table} 
Table 1: The content and composition of phenolic compounds in flat peaches from Xinjiang (mg/100 g FW). tent with previous research findings [68].