Good morning students! Please take your seats, take out your notebooks and open up your minds to learn something new. Welcome to room 20, where you are going to take advanced iris class today. Why iris? – someone may ask. We are taking a study of iris because according to Undina-ian calendar February of 2018 is proclaimed as a Month of Irises. My name is Mr. Chemist and I will be your teacher for today. I assume that you all love iris if you’re here today, which is an ideal situation for any teacher – to have a group of students who really want to learn something about the topic.
The name iris derives from ancient Greece where it meant ‘rainbow’ and where it was also used as the name of the goddess of the rainbow, Irida. It is believed that iris was given as a name of this flower due to its multiple possibilities of blooming colors. Oddly enough iris flower is considered odorless. Other animals with more sensitive noses can probably smell it but for humans it’s basically impossible to detect an iris scent from a flower. How can it be used in perfumery then? The truth is that most important part of iris is not its flower, but its root. That’s where all the ‘magic’ happens.
Orris root, as it is called by professionals has a long way to go before it will be ready for use in a fragrance & only two species: Iris germanica and Iris pallida are being commonly used for that. After iris blooming time their rhizomes (roots) are being harvested. Once collected they have to be thoroughly cleaned from ground and dirt, peeled, then they are cut into smaller pieces. Clean and chopped iris rhizomes are ready to undergo a process of drying, then aging. Dried root pieces will continue to age in controlled environment for as long as 3 to 5 years. At that time chemical reactions will take place.
This is one of the most important parts in a production of iris as a perfumery ingredient, because final efficiency of a harvest is depending on how well the reactions inside rhizomes will go. So, anyone knows what types of reactions happen during those 5 years of maturing? Chemical compounds of oils and fats inside orris root usually undergo two types of reactions. First of all there is a degradation reaction – a process in which big, heavy molecules break down into smaller ones due to destroying of some chemical bonding. Second, in my opinion more important process is oxidation.
Oxidation, as you might have guessed from the name of the reaction type is a process in which an atom of oxygen gets ‘attached’ to an organic compound and new bond (usually between carbon-C and oxygen-O) is formed. This leads us to irones – a very important carrier of a fragrance that we associate with iris. Triterpenoids found in orris root slowly oxidize over time and form alpha-irone (below, upper structure) and gamma-irone (below, lower structure). Their general chemical formula is C14H22O. Structurally they are similar to ionones – group of aroma compounds found in rose oil. Scent of irones is described as sweet, floral, woody, iris, ionone. It’s a very valuable molecule.
Once the whole process of aging and maturing of dried rhizomes comes to an end they are steam-distilled. This process draws out fragrant compounds from the inside of orris root pieces. In the distiller receiver you obtain an oily fraction that will solidify when it cools down due to high content of myristic acid (up to 85%) – what you obtain is an iris butter (or iris concrete) which usually has 13-17% of irones. If you wash iris butter with a 95% alcohol you’ll obtain iris absolute, richer in irones (generally up to 75% of them). Orris concrete and absolute possess a heavy, tenacious aroma.
Olfactory profile of both is also reminiscent of violet, since violets also contain irones as one of their fragrant compounds. Iris in perfume is also known for its extreme value. Because 1000 kg of orris root produces only around 2 kg of iris butter (yield of 0,2%) it ranks as one of the five most expensive raw materials. Iris absolute is 5 times more expensive than concrete due to much higher concentration of precious irones. For that reason natural iris is only used in most exquisite and luxurious perfume creations. Modern chemical synthesis found a way to produce synthetic irone (6-methyl alpha ionone) but it doesn’t have the same superb quality as natural product.
Because iris is so expensive it is never used in abundance but even 0,1 – 0,2% of it in a perfume formula will bring a touch of cold elegance with hints of floral, powdery or more buttery tones. I hope you found this class a valuable lesson that will help you to appreciate iris even more. Now that you understand the whole process of obtaining iris butter and iris absolute, as well as motifs behind its price, it should be much easier to love your iris fragrances even more. Before you leave I’d like to share with you this gorgeous journey of iris video from IFF. Professor Undina also asked that you sign on to the attendance list with your iris scent of the day. Class dismissed, off you go!