## 4 Conclusions  
In this study, the physicochemical characteristics, phenolic compounds, antioxidant activity, and volatile compounds of flat peaches were investigated in terms of taste, antioxidant capacity, and odor characteristics, constructing an aroma fingerprinting of flat peaches from Xinjiang. These results suggest that flat peaches have the trait of high sugar-low acid; the total sugar content of the flat peaches ranged from 43.01 mg/g FW to 142.64 mg/g FW, and sucrose (63.86-73.86%) was the main sugar. Meanwhile, the total organic acid content of the flat peaches ranged from 6.54 mg/g FW to 12.70 mg/g FW, and the organic acids were dominated by malic acid (5.93-14.96%) and quinic acid (5.25-15.01%). The ratio of fructose to sorbose was found to be approximately 1:1, and the ratio of malic acid, quinic acid, citric acid, and succinic acid was approximately 2:2:1:1, which might be one of the reasons for the special taste of flat peach. Flat peaches possess a high level of phenolic compounds, which endue the flat peaches with high antioxidant activity. The ABTS\({}^{+}\) and DPPH radical scavenging capacity in the flat peaches ranged from 165.40 to 324.38 umol TEs/100 g and 207.93 to 799.16 umol TEs/100 g, respectively. The CUPRAC reducing capacity of the flat peaches ranged from 44.69 to 1145.90 umol TEs/100 g and the FRAP reducing capacity of the flat peaches ranged from 57.56 to 1252.00 umol TEs/100 g. Chlorogenic acid (0.22-32.29%), epicatechin, rutin, catechhin, proanthocyanidin B1, and neochlorogenic acid were positively related to the antioxidant activity of the flat peaches. In addition, the aroma characteristics of the flat peaches were systematically characterized, and the volatile compounds of the flat peaches were found to consist of four alcohols, two acids, eighteen aldehydes, five ketones, nine terpen, sixteen esters, seven lactones, and two terpen. Among them, aldehydes (especially benzaldehyde and 2-hexenal) and esters were the main volatile components. A total of 20 common volatile compounds between flat peaches and nectarines were found in the study, indicating that flat peaches and nectarines have some similarities. However, the flat peaches had unique odor characteristics. A total of 27 common volatile substances were identified in the flat peaches, of which hexanal, 2-hexenal, nonanal, decanal, benzaldehyde, 2,4-decadienal, dihydro-\(\beta\)-ionone, 6-pentylpyran-2-one, 2-hexenyl acetate, ethyl acrylate, \(\gamma\)-decalactone, and theaspirane constituted the aroma fingerprinting of the flat peaches from Xinjiang. In particular, 2,4-decadienal, theaspirane, and 2-hexenyl acetate could be used as tracers, which can help to quickly distinguish flat peaches from other peaches by aroma criteria. Additionally, the odor characteristics of the flat peaches from Xinjiang were distinctly \"peach-like\", \"fruit\", and \"coconut-like\". This study was only a preliminary study on the aroma characteristics of flat peaches from Xinjiang. In the future, the formation mechanism of flavor in flat peaches can be studied in depth using techniques such as metabolomics to lay the theoretical foundation for the development of the industry of flat peaches in Xinjiang.