Essential oils storage

It is not only lipids but also essential oils which are sensitive to oxidative changes on storage. Sometimes stabilised by synthetic or natural antioxidants, they usually contain substances showing moderate antioxidant activity, but these may be lost by evaporation or oxidised by air oxygen unless more powerful phenolic antioxidants are added. 

The leaves harvested in summer gave the highest oil recovery (1.84%) and eugenol content (83%), whereas in the rainy season, the concentration of esters, namely, eugenyl acetate and benzyl benzoate, were comparatively higher (Kaul et al., 1996). Cinnamon leaves affected by leaf spot disease yielded less oil (1.2%), but the eugenol content was unaffected (Kaul et al., 1998). Rao et al. (2006) reported that the essential oil content (1.9-2.2%) and the chemical composition of C. verum leaves were not affected by storage up to a period of 15 months. 

Rao, B.R.R., Rajput, D.K., Kaul, P.N., Bhattacharya, A.K. and Naqvi, A.A. (2006) Effect of short and long-term storage on essential oil content and composition of cinnamon (Cinnamomum verum Bercht Presl.) leaves. Journal of Spices and Aromatic Crops 15(1), 1 9-24. 

Pascual Villalobos (2003) found the potential of plant essential oils against stored-product beetle pests. Coriander oil (10 pi) showed activity against the bruchid Callosobruchus maculates, the cereal storage pest. 

It is generally accepted that storage conditions for essential oils are important. The aromatherapist should keep oils in sealed bottles made of dark glass to protect them from the air and light, which can cause deterioration through chemical reaction. Keeping the bottles cool will slow any remaining reactions that could affect the oil s composition. 

Essential oils are mixtures of different chemical compounds and the composition will vary according to factors such as source, age, storage conditions and chemotypes of those compounds. Mixtures have properties that reflect all of their components, so by looking at the different compounds in an oil we can see how they not only have effects on different physiological systems in the body but can also complement each other. The fact that they are mixtures allows us to identify their components and analyze them with techniques such as chromatography. 

There is some concern about sensitisation with essential oils high in linalool, geraniol and citronellol. However, pure linalool is not a sensitiser. It is the oxidation products such as hydroperoxides that have been shown to have sensitising properties. Due to the oxidation hazard the correct storage and handling of essential oils containing these alcohols is important, (see Chapter 8)... 

Careful storage of essential oils high in aldehydes is crucial. Over a period of time, or in poor conditions, the oxidation of the aldehydes to acids will render them useless for aromatherapy. 

Using this knowledge we can appreciate that the composition of essential oils will depend upon a number of factors including methods of processing and storage. Essential oils are also subject to adulteration which can have dangerous consequences for the aromatherapist. 

The quality of an essential oil and its composition have been evaluated in terms of the methods used to extract it from the plant. It will be affected by types of solvent, heat, pressure and time of the processing. The oil will also reflect the quality of the plant material used, which depends upon its age, harvesting method, conditions of storage and any impurities present. The method of growth... 

It should be remembered that the analysis for any substance, including essential oils, can only be true for that substance at the time the tests were performed. The composition of oils can subsequently change with handling and storage, so by the time it reaches you, or by the time you use it, it may have a very different composition. 

In conclusion, the general storage rules for essential oils would be store in tightly stoppered, small, dark glass bottles that will be used up quickly with minimal times of opening to prevent entry of air or loss of volatile components. They should be stored at cool temperatures and used within a year of purchase. 

---