Italian Orris Butter is of the highest quality and is obtained by steam distillation of seasoned iris root. The iron content depends on the seasoning of the rhizome and the enrichment process during distillation.
3-BUTEN-2-ONE, 4-(2,5,6,6-TETRAMETHYL-2-CYCLOHEXEN-1-YL) is the scientific name for α-irone. Other isomers of this molecule are known: β-irone and γ-irone. Identified as responsible for the characteristic odor of this plant by Tiermann and Kruger in 1893, it has a pungent and unpleasant odor on its own, but when diluted in alcohol, it takes on the odor of violets. It has a boiling point of approximately 285°C and is semi-solid at room temperature. Its aroma is much more delicate than ionone (its chemical isomer, also present in α-, β-, and γ- forms). In the head portions of the orris distillation, we find furfural, benzoic aldehyde (allergens according to the IFRA standard), nonyl aldehyde, decyl aldehyde, and more; in the tail portions, sesquiterpene alcohols.
A major problem in the steam distillation of orris is myristic acid. This acid (also called tetradecanoic acid) is a fatty acid present in up to 75% of nutmeg (hence its name) but also in vegetable oils such as coconut and palm. It boils at 250°C but evaporates at 100°C when steam distilled. The physical and chemical behavior of this molecule can be advantageous on the one hand, but on the other, it solidifies at 49-51°C, generating a lot of foam during distillation. During processing, it must be removed, and appropriate technologies are required to obtain quality butter. It is also responsible for corrosion of distillation equipment.
Production of Iris Butter began around 1910; before that time, only an alcoholic extract was available. In the future distillation methods will became more refined, and the market began to find very pure concrete essence.
A distillation process typically lasts about thirty hours. Iris butter contains no residual solvents; it is typically light in color, has a waxy consistency, is slightly oily, and has a strong, talc-like odor. Its color should be white, tending towards yellow, but sometimes it turns gray due to manufacturing defects. It is insoluble in water but moderately soluble in alcohol. The VOC content varies from 2 to 12% depending on the processing method. Higher concentrations are also available, but the price skyrockets. It is always recommended to store iris concrete in glass-lined aluminum containers. It is a very expensive raw material for perfumery.
As with Iris Absolute, the scent is reminiscent of violet (Viola Odorata), but much softer and more elegant. High-end perfumeries use it not only as a fixative but also as its primary olfactory notes.