## 1 Introduction  
The diversity of volatile compounds is responsible for the unique flavors each food matrix expresses. Aroma is a particularly important and valued feature that illustrates the complex mixture of volatile compounds in foods. The human nose can sense a broad selection of volatile compounds. Although many studies focus on the volatile profiles of various fruit and vegetables, there is a particular need to enhance the available information.  
Peaches and nectarines are aroma-dense fruits with a specific, pleasant, and recognizable aroma [1]. Nectarines (_Prunus persica_ var. nectarina) may have developed from peach seeds, but their origin is still unknown. The peach (_Prunus persica_ [PERSON]), also known as Persian apple, is native to China and Iran. Subsequently, it has spread worldwide. Peaches have a large number of commercial varieties with different shapes, sizes, flesh colors (red, white, or yellow), skin types, seeds, among other variable aspects in relation to this popular fruit, representing a diverse international germplasm [2, 3]. The largest producer is China, followed by Italy, Spain, and the United States [2].  
The peach is a widely appreciated fruit for consumption, but has not yet been fully studied. The chemical composition of peaches depends on several factors, such as genotype, geographical and climatic conditions, seasonal and meteorological conditions, agronomic practices, stage of maturity, storage conditions, and processing methods [4]. In addition, it has been shown, over the years, that the phytochemicals are not evenly distributed in the fruit tissue; most are concentrated in the rind, particularly in the epidermal and subepidermal layers [5, 6, 7].  
Volatile compounds, together with sugars and acids, are the main chemical compounds that determine the characteristic aroma and flavor of foods. The peach species holds remarkable characteristics. More than a hundred volatiles have been identified in different peach varieties, with C\({}_{6}\) compounds, esters, benzaldehyde, linalool, C\({}_{13}\) ironisoprenoids, and lactones being the most abundant [8; 9]. In general, polyunsaturated fatty acids (PUFAs), such as linoleic acid (18:2) and linolenic acid (18:3), are the main precursors for aroma-related volatiles of peach fruit generated via the lipoxygenase (LOX) pathway or \(\beta\)-oxidation [10]. \(\beta\)-Oxidation leads to the production of the primary aroma in fruits, whereas the LOX system may account for the widest assortment of lipid-derived precursors of aroma compounds in disrupted plant tissues [11]. In addition to their contribution to fruit quality, peach volatiles are also important for the food and fragrance industry, where they are used as flavoring agents. A notable example of a sought-after industrial product with a peach-like aroma is \(\gamma\)-decalactone [12].  
Numerous studies demonstrated the large variability in the volatile compound composition of peaches depending on the cultivar, ripening stage, and geographical origin [13; 14; 15]. Nectarines generate fewer volatiles than peaches, but have more fruity and floral aroma notes due to greater ester, linalool, and terpinolene production [16]. Authors report changes in volatile aroma-related substances during peach fruit development and ripening after harvest [17; 18; 19].  
Although the volatile profiles of peaches have been generally widely studied, no information exists on Bulgarian peach varieties. Thus, the goal of this study was to investigate the difference in volatile profiles between eight peach and nectarine varieties in order to provide a tool to evaluate and compare the data on volatiles.