Changes in the chemical composition of essential oils during storage

Abstract

During the storage of essential oils, physical and chemical changes occur, leading to changes in the component composition, as a result of which the organoleptic and pharmacological properties of the oils change. The composition of the essential oils of Tagetes minuta L. and Cymbopogon flexuosus (Nees ex Steud.) W. Watson was studied by chromatography-mass spectrometry fresh and after storage. It was found that in T. minuta essential oil after storage for 6 months, the mass fraction of the main component, tagetenone, decreases due to the appearance of products of its oligomerization. Such changes lead to an improvement in the organoleptic properties of the oil. After storing the oil for 24 months, polymer forms of tagetones are formed in it and its viscosity is significantly increased, which makes its further use impossible. When storing C. flexyosus essential oil for 6 months, no changes were found in its chemical composition. After 24 months of storage, the mass fractions of cis and trans citral are reduced and undesirable components appear: isomeric forms of citrals, photocitral and caryophyllene oxide. Unpleasant notes appear in the aroma of the oil, and its quality decreases. Studies show that the chemical transformations of volatile components in essential oils do not always lead to a deterioration in their properties and depend on the species of the plant material and the duration of storage.