## 1 Introduction  
The Douro region, Portugal, is known worldwide for its wine production. However, other products, such as olive oil, demonstrate different characteristics compared with other areas of the country and even the world. This differentiation results from the soil and climate conditions that give its products a specific terroir. Volatile compounds are responsible for the aromatic profile of olive oils. This way, the functional groups belong to, and their proportions will influence the perceived aromas [1]. The primary step in the formation of volatile compounds occurs during milling, in which the rupture of the olive skin promotes the release of enzymes, which, in contact with triglycerides and phospholipids, cause their hydrolysis into free fatty acids, triggering a chain of enzymatic reactions, called the lipoxygenase (LOX) pathway. This pathway leads to the production of 13-hydroperoxides from the degradation of linoleic and linoleic fatty acids. These fatty acids, through hydroperoxide lysates, give rise to C6 aldehydes (hexanal, (_E_)-2-hexenal, (_Z_)-3-hexenal). The aldehydes are then reduced to alcohols (hexanol, (_E_)-2-hexenol, (_Z_)-3-hexenol) via alcohol dehydrogenase. These alcohols serve as a substrate for the alcohol acetyltransferase to produce esters (hexyl acetate and 3-hexenyl acetate) [2,3]. Although the LOX pathway is the main pathway for forming volatile compounds, others contribute to volatile compound profile in olive oils. Although less significant, amino acid fermentation,fungal enzymatic activities, or oxidative processes can be involved. However, it has been observed that an increase in volatile compounds produced by less significant pathways negatively influences the aroma of oils, with the appearance of undesirable smells [4]. Many volatile compounds in virgin olive oils are C5 and C6 compounds. In particular, 3-methylbutan-1-ol, hexanal, hexan-1-ol, and (_E_)-2-hexanal were found in most virgin olive oils in Europe [5]. The volatile compound profile is not significantly influenced by variations in the fatty acid profile. On the contrary, factors such as cultivar [1; 6; 7], geographic region [8], climate [8], fruit maturation stage [8; 9; 10; 11], and extraction conditions [5; 12; 13; 14; 15; 16; 17] are those that most influence olive oils' volatile profile. Volatile compounds that originate in the LOX pathway, such as hexanal, (_E_)-2-hexanal, (_E_)-2-hexan-1-ol, and pentanal, are mainly influenced by the maximum temperature at which the cultures are subjected. However, this influence does not prove to be direct, depending on other factors such as the cultivar. Also related to temperature is the altitude at which the crops are located, showing that olive oils produced in mountainous areas with lower temperatures are more bitter, spicy, and fruity compared with olive oils produced in places with lower altitudes and temperatures. Identifying the origin of the olive oils becomes difficult because variables such as the stage of maturation of the olive and the cultivar alter the chemical profile of the olive oils [8]. The different stages that intervene throughout the process of obtaining the olive oil can also influence the profile of volatile compounds, contributing to a set of characteristic olfactory and gustatory sensations. Several authors have described the relationship between the aromas perceived in olive oils and the volatile compounds identified [5; 6; 8; 18; 19]. However, aromas and sensory attributes are not associated only with a specific volatile compound but with the interaction of several compounds simultaneously [5]. Thus, this work aimed to determine the relationship between the perceived sensory attributes and the volatile compounds identified in the olive oils produced in Portugal's Douro Valley region.