## 1 Introduction  
The peach (_Prunus persica_), belonging to the Rosaceae family, is widely cultivated in 80 areas and nations around the world, such as America, Japan, and China [1]. The flat peach (_P. persica_ L. _[PERSON] var. compressa Beam_), a kind of peach like a saucer or doughnut, originated in the Xinjiang region in the northwest of China and has been cultivated for over 2000 years [2, 3]. Flat peaches are widely grown in Xinjiang, mainly in the Shihezi, Usu, Kashgar, and Yili regions [4]. What is more important is that the \"the flat peach of 143 rd regiment in Shihezi\" has been officially approved by the Ministry of Agriculture and Rural Affairs of the People's Republic of China for registration and protection of geographical indications for agricultural products ([[http://www.moa.gov.cn/govpublic/ncpzlaq/2017](http://www.moa.gov.cn/govpublic/ncpzlaq/2017)]([http://www.moa.gov.cn/govpublic/ncpzlaq/2017](http://www.moa.gov.cn/govpublic/ncpzlaq/2017)) 04/t20170424_5580538.htm, accessed on 20 April 2017). Xinjiang has a typically temperate and continental climate with ample sunlight, a massive temperature distinction between day and night, and lengthy sunshine hours, which endue the excellent quality of flat peaches [5]. Because of its sweetness, taste, and charming fruit aroma, flat peaches have become a popular table fruit in Xinjiang and are sold all around the world [6]. The acceptance of consumers plays an important role in the judgment of fruit quality. Organoleptic attributes (including SSC and TA, texture) and qualitative attributes (including sweetness and acidity) are important indicators for consumers to evaluate the traits of the fruit [7]. Taste is the first impression the fruit gives to the consumer. As a well-known table fruit, the flat peach possesses juicy flesh, a non-melting texture, and high sugar-low acid properties, which endue the flat peach with a good mouthfeel [8]. Sweetness and acidity are also among the most important quality indicators of the fruit's appeal to consumers. There is some research suggesting that flat peaches contain high levels of organic acids (especially malic acid, quininic acid, and citric acid) [9; 10] and soluble sugars (including sucrose, fructose, and glucose) [11]. In addition to its organoleptic and qualitative properties, the flat peach is endowed with functional properties due to the presence of amino acids, vitamin C, and high levels of antioxidant substances (especially phenolic compounds) and other bioactivity [12]. Modern clinical studies have proven that phenolic compounds and their meal substrates have anti-proliferative, anti-inflammatory, immunomodulatory, cardiac, neurological, and liver-shielding effects on the human body [13]. It is proven that the major phenolic compounds in the flat peach are usually procyanidin and quercetin, and these compounds are associated with antioxidant potential [14; 15; 16]. Apart from the inherent taste, texture, and nutritional properties of the fruit, the aroma is also an important quality characteristic [17]. Fruits often have their own distinctive and typical aroma characteristics. With headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) being widely used for the detection of volatile compounds in various types of fruit, more and more aroma substances that contribute significantly to the odor of peaches are being determined [18; 19]. Until now, over 100 volatile compounds in peach fruits have been identified [20]. It is believed that the flavor compounds of peaches consist of esters, lactones, aldehydes, alcohols, and ketones [21; 22], especially heptanal, 2-hexenal, and octanal [23]. These compounds give the peach a distinct \"peach-like\" and \"fresh and grassy\" flavor [24]. Studies have shown that the flavors of peach fruits are relatively similar, but there are differences between varieties.