The unique flavor of virgin olive oil (VOO) is attributed to its volatile compounds that develop from linolenic and linoleic acids through various enzymatic reactions. During storage of VOO the oxidation of the fatty acids begins and reduces the quality and the nutritional value of VOO. Volatile oxidation products, responsible for the off-flavor in rancid samples, then dominate pleasant volatile compounds.

Maria Tasioula-Margari and Kali Kotsiou, University of Ioannina, Greece, analyzed the changes in the quality characteristics of VOO stored for 18 month by solid phase micro-extraction-gas chromatography mass spectrometry (SPME-GC-MS). Even after 18 month of storage the quality characteristics, determined by the European Community, such as free acidity and peroxide values, are still met and the volatile compounds responsible for the positive flavor remained stable. However, high rates of formation of volatile oxidation products, such as heptanal, 2-heptanal and pentanal, are also observed. These are responsible for the off-flavor.

This real-time experiment provides better understanding of the auto-oxidation processes taking place during storage than ordinary accelerated oxidation tests.

• Changes occurring in the volatile composition of Greek virgin olive oils during storage: Oil variety influences stability
  Kali Kotsiou, Maria Tasioula-Margari
  Europ. J. Lipid Sci. Technol.2014.
  DOI: 10.1002/ejlt.201400231