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Natural essential oils play an important role in our formulations. They can be found in our WALA Medicines and Dr. Hauschka Skin Care products. These oils are only ever extracted using physical processes, usually steam distillation. The oil yield is extremely low in relation to the raw plant material used: generally in the one or two-digit range per mil. To obtain one litre of essential rose oil, for example, requires around four tonnes of rose flowers. Until the early 1970s, rose oil was even more expensive than gold.
The mysteries of essential oils
Today, natural essential oils are becoming an increasingly important commodity –not only for pharmaceuticals and cosmetics, but also in the food industry. Essential oils are multi-component mixtures. They are made up of numerous lipophilic (i.e. fat-soluble) and volatile compounds from a wide range of different chemical classes. But while they are very versatile, they are also extremely sensitive.
It is well known that essential oils are susceptible to reactions that cause them to change and degrade: contact with air, light and heat initiates oxidation and polymerisation processes. These processes can result in loss of quality and changes in the oils’ properties. Yet very little is known about the specific course these change processes take during storage and transport.
A methodological approach to research
To make sure our oils maintain their premium, quality, a WALA research team took it upon themselves to investigate the factors that can alter the stability of essential oils. Dr. Claudia Turek, who was a PhD student in the WALA Department of Phytochemical Research, wrote her thesis on the subject. Focusing on individual essential oils, she investigated the influence of temperature, light and oxygen on various degradation pathways.
Her methodological basic research produced new, very practice-oriented findings. By carefully monitoring and deciphering the change processes, Claudia Turek and her research team employed a parameter that had never previously been used in this context. This approach brings a whole new level of precision to determining the aging process and thus the quality of an essential oil, i.e. to map the result of all the oil’s oxidation processes. In addition, the newly discovered parameter can be used to predict the future course of the degradation processes, allowing for predictions to be made about the storage conditions required to slow down and, at best, stop the aging process – a revolutionary discovery.
Different storage conditions for each oil
The methodological basic research and the scientists’ work with essential oils of various origins provided yet another insight: there are no general optimal conditions under which all essential oils are equally “happy”. Each individual mixture of lipophilic components reacts completely differently to the influences of temperature, light and oxygen.
The ideal storage conditions must therefore be laboriously determined for each individual oil to ensure that these valuable ingredients maintain their quality. This is a challenge that we are only too happy to take on here at WALA. We are also keen to share our findings with the rest of the industry. Because we want the knowledge that we acquire through research conducted in cooperation with universities to be available to the world.
Properly stored oil has low allergenic potential
The title of Claudia Turek’s PhD thesis “Stability of Essential Oils” may sound rather theoretical to a scientific layperson, but the findings from the research team’s basic, methodological research are actually very practical: they help to keep the allergenic potential of essential oils low.
It is known that new molecules are created by the oxidation and polymerisation processes triggered by light, heat and air. And it is these by-products of the aging process that can cause allergic reactions – pure essential oils have hardly any allergenic potential themselves. The practical finding from this basic research is that well-stored essential oils produce fewer hypersensitivity reactions than oxidised oils.
But it doesn’t stop there
The International Fragrance Association (IFRA) in Brussels, which is responsible for defining and implementing standards for the use of essential oils, also found the WALA research group’s findings new and surprising. This new knowledge was deemed so valuable, in fact, that the IFRA invited us to become actively involved in the association’s future work. Since then, WALA has been in regular cooperation with the IFRA.
We see our active participation in the work of this association as a real stamp of approval for our scientific work – but we are not resting on our laurels. We are already researching ways to refine the methodological analysis of essential oils: by isolating individual substances and analysing their respective oxidation and change processes, we can provide an even more specific guarantee of the quality of each and every essential oil.
Turek C, Stintzing FC. Evaluation of selected quality parameters to monitor essential oil alteration during storage. Journal of Food Science 2011, 76, C1365–C1375.
Turek C, Stintzing FC. Impact of different storage conditions on the quality of selected essential oils. Food Research International 2012; 46: 341–353.