Turkish Virgin Olive Oils Key Odorant Compounds: A Review

Abstract

Virgin olive oil, a premium culinary oil, is highly prized for its delicious taste and aroma components in the world. It is particularly important in the basic Mediterranean diet. Aroma is one of the most critical quality criteria influencing consumer acceptance of olive oils. More than 300 aroma compounds have been identified in olive oil; however, only a small fraction of these compounds are responsible for its characteristic aroma and are referred to as aroma-active compounds. Gas chromatography coupled with olfactometry is commonly used to identify aroma-active compounds. In addition, methods such as dilution analysis, frequency detection, and time–intensity techniques are employed to determine these compounds. Using the odor activity values (OAVs) obtained through these methods, the individual contribution of each aroma compound to the characteristic aroma of olive oil can be calculated. The number and concentration of aroma-active compounds in olive oil vary depending on numerous factors, including the olive cultivar, ripening stage, climate, production, and storage conditions. Turkey is among the leading countries in olive oil production worldwide. The most prominent olive cultivars in Turkey include Ayvalık, Beylik, Gemlik, Memecik, Halhalı, Haşebi, Kilis Yağlık, Nizip Yağlık, Domat, Sarı Ulak, and Tavşan Yüreği. The most important groups of volatile aroma compounds responsible for the characteristic aroma of olive oil are five- and six-carbon alcohols, aldehydes, and their corresponding esters. These are followed by terpenes, ketones, and carboxylic acids. Aroma and aroma-active compounds in olive oil are mainly formed through the lipoxygenase pathway during oil extraction from olives. In this pathway, aldehydes are formed from fatty acids, which are then reduced to alcohols by alcohol dehydrogenase (ADH), and further converted into esters by alcohol acyltransferase (AAT). Among the aroma-active compounds, hexanal (associated with a cut grass odor), octanal (citrus-like), and 1-penten-3-ol (oily odor) stand out due to their high OAV values. This review aims to examine the aroma-active compounds present in Turkish olive oils.