October 20, 2005
The exact chemistry of olive oil flavor still puzzles researchers. Some strong flavors are comprised of a single compound. The simple chemical cinnamaldehyde imparts a strong smell of cinnamon. It would be nice to identify a single chemical such as this in olive oil which could predict good or bad taste; we would have no need for tasters but could just do a simple test. Unfortunately, there are thousands of chemical compounds in olive oil and the interaction of hundreds of these probably contribute to flavor.
Naturally Occurring Aroma Compounds in Virgin Olive Oil
The delicate flavor of quality extra virgin olive oil is related to the presence of a large number of chemical compounds. These flavor compounds comprise aliphatic and aromatic hydrocarbons, aliphatic and triterpenic alcohols, aldehydes, ketones, esters, furan and thiophene derivatives. Over 100 such compounds have been identified which, as a whole, contribute to the distinctive organoleptic characteristics which make extra virgin olive oil so select. These aroma compounds form part of the unsaponifiable fraction, which makes up about 1% of the oil.
These tastes and fragrances derive from compounds like hexanal (green, grassy), trans-2-hexenal (green, bitter), 1-hexanol and 3-methylbutan-1-ol, which are the major volatile compounds of olive oil. Many of these flavor compounds decompose if temperatures during milling exceed 30°C. Thus the importance of “cold pressing”.
What determines whether these compounds are present?
- The care which went into growing, harvesting, pressing and storing
- What time of year the olives were picked - whether green or ripe
- The variety of olive
- The weather - water, freezing, heat
What is the chemical or component in the olive oil that is peppery and sometimes makes people cough? Is it oleic acid?
It is not oleic acid because all olive oils have about the same amount and they are not all peppery. Many studies have been done to try to predict a flavor profile based on an oil's chemistry. In "The Handbook of Olive Oil" by Harwood and Arapicio they cite studies done by the authors which show that aglycons are responsible for the bitter and pungent sensory attribute, as well as tyrosol and possibly alpha-tocopherol. The phenols are related to astringent attributes. It is probably the combination of bitterness and astringency that causes the cough.
Gary Beauchamp and other chemists published a September 1, 2005 article in Nature which shows that Oleocanthal, the pungent compound in some oils which creates a stinging sensation in the throat, has similar properties to anti-inflammatory compounds such as ibuprofen.
Flavor Components of Olive Oil--A Review, A.K. Kiritsakis*, Department of Food Technology, School of Food Technology and Nutrition, Technological Educational Institution (TEI) of Thessaloniki, Sindos Thessaloniki, Greece.
Following is the abstract of a Journal of the American Oil Chemist Society which describes many of the volatile substances. Contact American Oil Chemists' Society (AOCS) for full article (or the author).
The unique and delicate flavor of olive oil is attributed to a number of volatile components. Aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds have been quantitated and identified by gas chromatographymass spectrometry in good-quality olive oil. The presence of flavor compounds in olive oil is closely related to its sensory quality. Hexanal, trans-2-hexenal, 1-hexanol, and 3-methylbutan-1-ol are the major volatile compounds of olive oil. Volatile flavor compounds are formed in the olive fruit through an enzymatic process. Olive cultivar, origin, maturity stage of fruit, storage conditions of fruit, and olive fruit processing influence the flavor components of olive oil and therefore its taste and aroma. The components octanal, nonanal, and 2-hexenal, as well as the volatile alcohols propanol, amyl alcohols, 2-hexenol, 2-hexanol, and heptanol, characterize the olive cultivar. There are some slight changes in the flavor components in olive oil obtained from the same oil cultivar grown in different areas. The highest concentration of volatile components appears at the optimal maturity stage of fruit. During storage of olive fruit, volatile flavor components, such as aldehydes and esters, decrease. Phenolic compounds also have a significant effect on olive oil flavor. There is a good correlation between aroma and flavor of olive oil and its polyphenol content. Hydroxytyrosol, tyrosol, caffeic acid, coumaric acid, and p-hydroxybenzoic acid influence mostly the sensory characteristics of olive oil. Hydroxytyrosol is present in good-quality olive oil, while tyrosol and some phenolic acids are found in olive oil of poor quality. Various off-flavor compounds are formed by oxidation, which may be initiated in the olive fruit. Pentanal, hexanal, octanal, and nonanal are the major compounds formed in oxidized olive oil, but 2-pentenal and 2-heptenal are mainly responsible for the off-flavor.
JAOCS 75, 673681 (1998).