Have you ever opened a bottle of essential oil to discover that this bottle’s scent seems a little different from the last bottle you purchased?
You may have felt alarmed or even a little uneasy.
Unlike perfumes that have a consistent scent all the time (it is easier to control scents when they are synthetically produced in the laboratory), Mother Nature’s plants and herbs are not made in the laboratory.
Scent variation within the same essential oil type is an indicator that it is nature-made and not man-made.
Plants and herbs grow in environments that depend largely on rain, sunlight, seasons, and soil. Even the time of harvesting makes a difference. The scent difference in your essential oil arises from these natural factors which influence the composition of compounds of harvested plants and therefore, upon distillation, their sometimes subtle and sometimes distinct scent differences.
Soil and Minerals
Soil and its minerals play a role in creating scent differentiation. Minerals such as nitrogen, phosphorus, and potassium are important to plants in developing organic compounds such as amino acids, protein, enzymes, and nucleic acids. For example, potassium helps plants by increasing their crop yield and quality. A study found that increasing the rate of potassium of the soil where the plant is grown greatly affects the proportion of components in the essential oils. The proportion of components in the plant material influences the scent in the resulting essential oil.
The environmental factor is a major influence in the chemical composition of essential oils.
A study carried out on a Brazilian medicinal plant called Lychnophora ericoides showed that the same plant specie grown in two different places harvested in two different seasons, summer and winter, produced essential oils with significantly varying composition. The researchers believe that environmental factors influence the chemical composition of the plant’s essential oil constituents.
Another study also found that the yield and composition of the essential oil obtained from different populations of Artemisia annua L. (Asteraceae), transplanted during different months were also found to differ greatly.
Harvest time also influences the chemical composition of the essential oil.
Thymus capitatus essential oil is harvested from the Thymus capitatus plant and yet the essential oil harvested at three different stages of the plant growth shows a variation in scent. The Arabian Journal of Chemistry notes three vegetative stages: before blooming, beginning of blooming, and full blooming stage. The profiles of the plant at the beginning of blooming and full blooming stages are quite similar both in composition and quantity of metabolites but quite different from before blooming.
Another study that looked at essential oil yields of the Turkish oregano found that the aromatic plant produced its maximum oil yield in mid-July with the highest concentration of carvacrol, a compound found in many aromatic plants. A distillation with a high concentration of carvacrol will certainly differ from a distillation with a low concentration of carvacrol and hence affect its scent profile.
Clearly, many factors influence the composition of compounds in essential oils and this, in turn, results in slight variations in the scent of the essential oils. The next time you find a slight scent difference in your essential oil and you know you bought it from someone you trust, never fear. It’s just Mother Nature at work!