Discovery on the stability of lemon essential oil

A multidisciplinary research study involving several Federican researchers from the Department of Chemical Sciences, the Department of Biology, the Department of Molecular Biology and Medical Biotechnology, and the Department of Chemical Engineering, Materials and Industrial Production has been published in the prestigious Journal of Essential Oil Research to study the chemical and microbiological composition of lemon essential oils from different cities in Sicily, which, by a fortuitous chance, have been kept hermetically sealed and in the dark for about 25 years.

Essential oils (EOs) are volatile natural compounds widely used in perfumery, the food and pharmaceutical industries and as solvents [1,2]. Although their nominal shelf life after opening is currently 12 months, their antibacterial and antiviral properties could allow them to last longer if stored properly.

This study investigated the long-term stability of lemon EO samples found fortuitously and stored in hermetically sealed glass bottles for 25 years. Comprehensive analyses were conducted to assess their chemical and biological properties. Gas chromatography with flame ionization detection (GC-FID) was used to compare the terpene component of the aged samples with that of an authentic organic lemon OE produced in the same geographical area and packaged in 2024. In addition, nuclear magnetic resonance (NMR) spectroscopy was used and microbiological tests were performed to identify and characterize a white-gray precipitate present in some samples. The results revealed that essential oils can retain their composition and, therefore, functionality well beyond their expected shelf life, suggesting significant opportunities for companies to reduce industrial waste and optimize storage practices.

Microbiological analysis showed the absence of contaminants in the 15 essential oil samples analyzed, while gas chromatographic analysis of the terpene component of essential oils showed that there were no appreciable differences between a recently produced essential oil sample and lemon essential oil samples stored for 25 years. These results look very important for the essential oil industry, whose products are currently guaranteed to be stored for at least two years. Conversely, the possibility of extending the shelf-life of lemon essential oils for at least 4-5 years should be evaluated based on the data obtained .