Furthermore degradation due to oxidation processes, activity of enzymes and microbes, processing conditions as well as storage results in flavour active carbonyls and alcohols like pentanal, hexanal, heptanal and 2-heptanone, also identified in oil samples (A) and (B). The outstanding high content of hexanal, representing the main component in both refined grape seed oils ((A): 25%, (B) 30%) results presumably from degradation of linoleic acid, grape oils‘ main fatty acid. The very high content of this substance can probably be concluded from the processing conditions including refining, as lower contents of hexanal were identified in the group of virgin grape oils (C)–(I).