## 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 composition and content of soluble sugars play a key role in consumer satisfaction and even determine the consumption of the best fruit [56]. In this study, the sucrose, fructose, glucose, and sorbitol contents of flat peaches (Qingpan, QP; Ruipan 2, R2; Ruipan 4, R4; Wanpan, WP) were determined. The results showed that sucrose, glucose, fructose, and sorbose accounted for 6.79-24.99%, 1.60-4.95%, 1.22-4.05%, and 0.39-4.34% of the total sugars, respectively (Supplementary Figure S1a). The contents of soluble sugar in flat peaches from Xinjiang were within 28.66 to 105.47 mg/g FW, 6.76 to 20.91 mg/g FW, 5.16 to 17.10 mg/g FW, and 1.66 to 18.31 mg/g FW, respectively (Figure 3a). The total sugar content ranged from 43.01 to 142.64 mg/g FW. R2 had the highest total sugar content, but QP had the lowest. Except for QP, the total sugar content of all three flat peaches exceeded 100 mg/g FW. The results were in agreement with earlier studies [57; 58]. Sucrose, fructose, glucose, and sorbitol are the major sugar components of peaches [59]. In this study, sucrose and glucose were the major sugars in flat peaches, accounting for more than 80% of the total sugars, which was consistent with previous studies [60]. It was easy to see that sucrose was the main source of sweetness in the flat peaches, and glucose was the second most important source. The presence of sugars gives the fruit its sweetness, and the intensity of the sweetness is determined by the amount of total sugar and the proportion of sugar components [61]. The ratio of fructose to sorbose was found to be approximately 1:1 in the current study, and the glucose content was higher than the fructose content. Based on a previous study, the fructose sweetness scale was higher than that of glucose and sucrose [62], so it could be inferred that fructose is the largest contributor to the sweetness of flat peaches. Of note, there was some evidence to suggest that the fructose content was higher than the glucose content in peaches [63]. This discrepancy could be attributed to different seasonal changes, climate, irrigation, or crop loads. According to previous reports, the content and composition of organic acids affected the acidity of fruits [64]. Four main organic acids, including quinic acid, malic acid, citric acid, and succinic acid, were determined from the flat peaches (Figure 3b). The results showed that the content of malic acid was highest, and the range was from 2.34 mg/g FW to 5.92 mg/g FW (5.93-14.96%) (Supplementary Figure S1b). Quinic acid (5.25% to 15.01%), which ranged from 2.07 mg/g FW to 5.93 mg/g FW, was the second most abundant organic acid after malic acid in the flat peaches. Succinic acid and citric acid made up a relatively small proportion of the organic acids in flat peaches, accounting for 14.08% and 8.14% of the total organic acid content, respectively. Among them, the succinic acid content ranged from 0.78 mg/g FW to 1.89 mg/g FW (1.97-4.78%) and the citric acid content ranged from  
Figure 3: Soluble sugars (**a**) and organic acids (**b**) in flat peaches from Xinjiang (mg/g FW). Significant variations at a level of \(p\leq 0.05\) (Duncan’s test) are shown by different letters for each sample. 0.61 mg/g FW to 1.09 mg/g FW (1.55-2.75%). The current study showed that the total organic acid content of flat peaches ranged from 6.54 mg/g FW to 12.70 mg/g FW, with R2 having the highest total organic acid content, while QP was the lowest. Several studies have shown that malic acid and citric acid were the main organic acids in peaches [41; 60]; this was in line with our results. These results would seem to suggest that the content of organic acids in peach fruits was a discussable issue in identifying the style of peach. The results of this study showed that malic acid was the main source of sourness in the flat peaches, comprising 39.86% of the total organic acid content.