Orris oil

Orris root oil is obtained by steam distillation of the rhizomes of the sweet iris, Iris pallida Lam. (Iridaceae), cultivated in the Italian province of Tuscany and in China, or Iris germanica L., cultivated inMorocco. Prior to distillation, the rhizomes are stored for several years and are then ground.The steam distillate is a light yellow to brown-yellow solid mass with a violet-like odor.The solid liquefies to a yellow to yellow-brown liquid at 38–50 ℃. Acid number: 175–235, corresponding to an acid content of 71–95% (calculated as myristic acid); ester number: 4–35; ketone content (calculated as irone): 9–20%; soluble with ethanol in all proportions at 50 ℃. Because of its high content of myristic and other fatty acids, the steam distillate is a waxy mass that resembles a concrete and is sold under this name or as Beurre d’Iris (Orris butter). In addition, a neutral product, obtained after removal of the acids with alkali, is marketed under the name orris oil absolute or as orris oil 10-fold. The main constituents of the oils are cis-γ-irone (usually 30–40%) and cis-α- irone (usually 20–30%), which are also responsible for the typical odor. I. pallida oil contains the dextrorotatory enantiomers while I. germanica oil contains the levorotatory enantiomers. Most of the processed orris products are derived from I. germanica roots grown in Morocco. Fresh orris roots do not contain any irones. These compounds are formed by an oxidative degradation process from higher molecular precursors, the so-called iridales, only when the dried orris roots are stored for a longer period. To avoid such a time-consuming procedure, microbiological or special fermentation processes have been developed. The oil is very expensive and is used in perfumery and in flavor compositions.