Impurity or Minor Component?

This past week we performed the hydrodistillation (steam distillation) of spices to produce essential oils. This year, students chose between Anise, Fennel, Cloves, Cumin, and Oregano for their spices. This was the first time we used Fennel and Oregano. The yield of Clove oil still surpasses the other spices but analysis by TLC, UV, and GC-FID is still doable for all the oils. As expected the GC-FID revealed that the essential oil was composed of a major component which is typically a known compound (anethole, eugenol, cuminaldehyde, or carvacrol) and several minor components of unknown identity. In their reports, many students identified the minor components and “impurities” in the sample. This must come from a synthetic chemistry mindset where any compound which is not the target product is considered to be a contaminant. In the case of essential oils, however, the minor components are considered to be the factors that give a particular essential oil its body and character. In addition, a minor compound is as likely as a major component to have some desirable aromatic and/or medicinal quality. I think that there is a life-lesson in there somewhere. The major components attract all the attention and are frequently identified as those chemicals which determine the characteristics of an oil. However, a case can be made that the small things are really the most distinctive and interesting even though they don’t stand out in let’s say a TLC, UV spectrum, or GC chromatogram.

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