## 1 Introduction  
Coffee is one of the most consumed beverages worldwide and has positive effects on health [1; 2]. Coffee consumption is attributed to the psychological stimulation induced by caffeine, the sensory pleasure given by coffee aroma and flavor, and the beneficial health effects [3]. Moderate coffee consumption has been reported to have health benefits, such as reduction in the incidence of several chronic disorders, including diabetes [4], hypertension, and Alzheimer's and Parkinson's diseases [5; 6; 7; 8], as well as liver and kidney pathology [9; 10; 11; 12; 13]. Moreover, the identification of polyphenols and antioxidants in coffee has further enhanced its consumption. The degree of loyalty to a specific coffee brand depends on external factors, such as label, brand, packaging, price, and marketing, and on consumers' emotional responses to coffee taste. Therefore, research on the quality parameters that define the sensory quality of coffee, i.e., volatile organic compounds (VOCs), has increased in recent decades [14; 15]. According to the International Coffee Organization, worldwide coffee-bean production in 2020 was about 99 million bags of Arabica and 70 million bags of Robusta [16]. The most common and economically important coffee varieties are Arabica and Robusta, representing over 90% of global coffee production [6]. Based on its sensory quality, Arabica(_Coffea arabica_ L.) is classified into strictly soft, soft, barely soft, hard, rioysh, rio and rio zona. In contrast, Robusta (_Coffea canephora_) has woody and earthy flavors and is classified into four categories: excellent, good, regular, and abnormal [6; 17]. The Arabica varieties are considered to have better sensory characteristics and, consequently, higher purchasing prices than the Robusta varieties [2; 6]. Green coffee contains insoluble polysaccharides (-50%), soluble carbohydrates (6-12%), lipids (8-18%), proteins and free amino acids (9-12%), minerals (3-5%), and polyphenolic compounds [1; 7; 8; 18]. The most important alkaloid in green coffee is caffeine, the content of which strongly depends on variety and growing conditions [1; 2; 6; 7; 18]. Green-bean composition varies according to coffee variety, agricultural practices, climate, terroir, harvest, and post-harvest practices. The roasting of green beans is the critical step that determines the composition of the roasted beans, although grinding and storage may also influence composition. The influence of coffee species and varieties, geographical origins, harvesting, roasting, grinding, and brewing on the quality of coffee, from raw beans to the final cup of espresso coffee, has been extensively studied [19; 20]. Coffee quality depends on many factors, such as the production system, the chemical composition of the green or roasted beans, the roasting process, and brewing [17; 20; 21]. The multiple chemical reactions (Maillard reaction, caramelization and Strecker degradation, polyphenol degradation, polymerization of carbohydrates, and pyrolysis) that occur during roasting affect the color, flavor, and aroma of coffee [17; 20; 22]. During roasting, the formation of undesirable or toxic compounds, such as polycyclic aromatic hydrocarbons and acrylamide, is also possible [22]. Grinding roasted coffee beans is crucial to releasing volatile organic compounds in the brewing of coffee [19]. The main constituents of coffee can also be affected by roasting conditions, ground-particle size, and brewing methods [20]. The composition of coffee allows for differentiation between varieties and the identification of geographical origins and production processes [23]. The content of elements reflects local environmental conditions, such as weather and soil composition, as well as added fertilizers and pesticides [24; 25]. Major and trace elements do not decompose during the roasting process; thus, their use as tracers for the authentication of provenance is easier than the use of organic compounds, which may be degraded by roasting temperatures [26].