Orris oil

Description

Perennial herbaceous plant that grows wild or can be cultivated. The various species are native to the Far East, but they are well acclimated to the Mediterranean regions as well. Their cultivation in Italy represents a flourishing industry.I. pallida Lam. is the best variety for extractive purposes, followed by I. germanica and I. florentina (which is cultivated mainly for ornamental purposes). Depending on the variety, the plant exhibits blue, deep blue, or whitish-blue veined flowers. It has an erect stem and radical leaves. It has large, horizontal, highly branched, and fleshy rhizomes exhibiting a pleasant and persistent odor. The fragrance of I. pallida is most persistent.
The peeled rhizomes (roots) are used after two years of aging. Commercial qualities include straight, twisted, and knotty rhizomes. Orris has a violet-like odor with a fruity undertone.
Orris concrete: Orris butter, or orris concrete, is obtained by steam distillation of dried ground rhizomes with yields ranging between 0.2 to 0.3%. Special techniques and prolonged distillation are required. It contains 13% to 17% ketones (sometimes more) calculated as irone; 83 to 86% free or partially esterified fatty acids (e.g., myristic); terpene and sesquiterpene alcohols; aldehydes; and esters. The physical-chemical constants vary, depending on the origin of the rhizomes. At room temperature, orris concrete from 1. pallida Lam. is a light yellow-brown solid mass with a violetlike fragrance; at 40 to 50℃ the product melts to a yellow to yellow-brown liquid.
Orris absolute: Obtained by alcoholic extraction of the concrete to separate the fatty acids and their esters. It may contain from 55 to 85% ketones (irone).
Orris resinoid: The resinoid is prepared by extracting the comminuted rhizomes with yields of 2.4 to 3.3% using benzene, or 1 to 2% using petroleum ether. An absolute can be prepared from the resinoid; this contains 62 to 78% ketones (irone).
The derivatives are fluid extract, concrete and absolute essence, resinoid, and the tincture (20% in 50 to 60% ethanol or 30% in 55% ethanol).

Chemical properties

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.

Chemical properties

Orris butter, or orris concrete, is obtained by steam distillation of dried ground rhizomes with yields ranging between 0.2 and 0.3%. Special techniques and prolonged distillation are required. The physical–chemical constants vary, depending on the origin of the rhizomes. The concrete has a violet-like fragrance. Orris Absolute: Orris absolute is obtained by alcoholic extraction of the concrete to separate the fatty acids and their esters. It may contain from 55 to 85% ketones (irone). Orris Resinoid: The resinoid is prepared by extracting the comminuted rhizomes with yields of 2.4 to 3.3% using benzene, or 1 to 2% using petroleum ether. An absolute can be prepared from the resinoid; this contains 62 to 78% ketones (irone).

Physical properties

At room temperature, orris concrete from I. pallida Lam. is a light yellow-brown, solid mass; at 40 to 50°C the product melts to a yellow or yellow-brown liquid. It is soluble in most fixed oils, mineral oil and propylene glycol. It is insoluble in glycerin.

Occurrence

Found in the rhizomes of Iris pallida. Lam. (Fam. Iridaceae) (Guenther. 1952; Naves, 1974).

Preparation

By alcoholic extraction of the concrete (Fenarolis Handbook of Flavor Ingredients. 1971).

Definition

Extractives and their physically modified derivatives. Iris pallida, Iridaceae.

Essential oil composition

The oil contains 13 to 17% ketones (sometimes more) calculated as irone 83 to 86% free or partially esterified fatty acids (e.g., myristic), terpene and sesquiterpene alcohols, aldehydes and esters.

Safety Profile

Low toxicity by ingestion. Whenheated to decomposition it emits acrid smoke andirritating vapors.