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PART 4 ­ AROMA CHEMICALS DERIVED FROM ESSENTIAL OILS

APPENDIX " H" CHEMICAL COMPOSITION OF SELECTED ESSENTIAL OILS

It is estimated that of the world's essential oil production, some 75% is used "as is" in either flavours (50%), phytotheraphy/aromatheraphy (5-10%) and fragrances (20-25%). Only 20 to 25% is used for isolate extraction. The value addition associated with essential oils is their use in formulations. This work is the work of formulators with organoleptic qualifications and skills. The reasons for the limited further "reworking" of essential oils include: · The additional costs do not yield significant benefits; · The "allure" of essential oils is in their natural complexity; · Where single molecules are required these are more economically produced synthetically. Those essential oils that are used to produce isolates are usually the bulk essential oils like citrus, eucalyptus and peppermint. The chemical composition of most essential oils are therefore of interest predominantly as an indicator of their organoleptic properties. Most essential oils have over a dozen different chemical constituents. As an illustration, the table below highlights the top 5 constituents (by percentage composition) of a selection of essential oils grown in South Africa. Oil selection Geranium Top five chemical constituents Geraniol (10-30% Citronellol (10-40%) Linalool (5-10%) Citronellyl formate (5-10%) Isomentone (5-10%) Isobutyl angelate (15-35%) Isoamyl angelate (10-20%) 2-methyl-2-propenyl angelate (5-15%) isobutyl isobutyrate (3-7%) a-pinene (2-6%) 1.8 cineole (20-50%) a-pinene (10-35%) Camphor (15-20%) Camphene (5-10%) borneol (5-12%) (Moroccan oils have more 1,8 cineole and French oils more a-pinene))

Roman Chamomile

Rosemary Oil (cineole type)

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Rosemary Oil (verbenone type)

Verbenone (5-30%) a-pinene (10-20%) 1,8 cineole (0-15%) Camphor (3-10%) Borneol (2-5%) Geranial (20-40%) Neral (15-30%) Geraniol (4-10%) Citonellal (2-15%) Geranyl acetate (1-4%) Neral acetate (1-4%) (Some strains produce excesses of Citronellal and Citronellol at the expense of geranial and neral)l Two main types: 1) Linalool rich: Linalool (60-80%) 1,8 cineole (2-12%) Camphor (3-8%) Borneol (3-5%) a-pinene (1-3%) 2) 1,8 cineole rich: 1,8 cineole (60-70% Linalool (5-15% a-pinene (2-4%) b-pinene (2-6%) a-terpineol (2-3%)

Lemon Balm (Melissa)

Marjoram (Spanish ­ Thymus Mastichina)

Majoram (Origanum majorana)

Other constituents Carvacrol 40-80%) y-terpinene (3-5%) p-cymene (4-5%) a-pinene (1-2% thymol (1-2%) Thymol (15-70%) Carvacrol (1-15%) b-pinene (1-3%) Myrcene (2-4%) Limonene (2-4%) (Some contain high levels of y-terpinene and p-cymene) Linalool (40-60%) Eugenol (2-20%)

Thyme oil

Basil oil

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1.8 Cineole (1-10%) methyl cinnamate (5-30%) methyl eugenol (3-5%) (there are types which are high in methyl chavicol, in place of linalool) Lavender Oil Linalool (20-40% Linalyl acetate (20-40%) 1.8 cineole (2-5%) camphor (2-4%) terpinen-4-ol (2-6%) 1,8 cineole (20-30%) Linalool (25-35% Camphor (10-30%) Borneol (1-3%) Linalyl acetate (1-3%) 1,8 cineole (3-7%) Linalool (20-40%) Camphor (5-10%) Borneol (1-3%) Linalyl acetate (20-40%) Neral (10-35%) Geranial (15-50%) Geraniol (3-5%) Linalool (1-2%) Limonene (0-5%) Isomentone (5-50%) Limonene (10-30%) Diosphenol (10-30%) 4-diosphenol (10-25%) menthone (2-25%) (Also containing novel sulphur hetreocyclics)

Spike Lavender

Lavandin Oil

Lemon grass (c. citrates)

Buchu (A. betulina)

1. Citronellol and its esters These are very important fragrance intermediates for soap and detergents and also when a rosy, fresh floral tone is required. Natural citronellol is obtained from geranium oil, known as rhodinol. This has only minimal production. Most commercial product is produced via synthetic routes via selective hydrogenation of geraniol/nerol. Citronellol is the dihydro analogue of geraniol/nerol. 2. Citronellal Citronellal has a fresh, green citrus character, and is used in flavour and fragrances. Citronellal is prepared via extraction of citronalla or Eucalyptus citriadora oil. More than 80%

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of the worldwide production, is however via the dehydrogenation or oxidation of citronellol (via geraniol. Another use of citronellal is in the production of menthol, hydroxycitronellal, and methyoxycitronellal. 3. Geraniol/nerol and their esters Geraniol and its esters have a mild sweet floral or rose character and very important fragrance and flavour ingredients. Geraniol/nerol are cis/trans isomers. They can be prepared by isolation from citronella oil or as is mostly the case, by various synthetic routes. Geraniol is produced from myrcene. 4. Linalool and esters Linalool and its esters are very important perfume ingredients with a lavender or bergamot odour. They are also important intermediates for the synthesis of Vitamins A, E and carotenoids. Natural linalool is extracted from rosewood oil. Commercial linalool is produced in large quantities via a variety of synthetic methods. alpha-Pinene is converted by catalytic hydrogenation to cis-pinane, which is oxygenated with a peroxide to cis-pinanol. This pinanol subsequently is pyrolised at high temperature to linalool. Linalyl acetate is prepared by the esterification of linalool with acetic anhydride. 5. Alpha terpineol and esters The lowest boiling and largest fraction from turpentine fractionation is alpha pinene. One use of alpha pinene is in the production of pine oil, which has a refreshing piney odour and finds high volume usage in cleaners, odourisers, and sanitisers. Synthetic pine oil is actually a mixture of terpene alcohols, chiefly alpha terpineol, along with smaller amount of other monoand bicyclic terpene alcohols. Pine oil contains 50 ­ 80% terpineol. Globally 80 ­ 85% of the pine oil produced is made by hydration of alpha pinene with aqueous mineral acid at room temperature to terpin hydrate and subsequent dehydration of this hydrate with phosphoric acid and simultaneous steam distillation of alpha-terpineol. The remainder comes chiefly from sulphate turpentine fractionation. Perfume grade alpha terpineol is a delicate floral, lilac-type odour, and is one of the most widely used of all perfume chemicals because of its low cost and stability. It also finds use in the flavour industry. Alpha Terpinyl acetate has a herbaceous bergamot-lavender odour and considerable quantities of it are used in low cost fragrances for household products. 6. Myrcene The greatest use of myrcene is as an intermediate in the commercial production of terpene alcohols: geraniol/nerol, and linalool, which serve as intermediates for the production of large-volume aroma and flavour chemicals. It is also used in large quantities in the manufacture of specialty aroma compounds (myrcenol and its derivatives). Copyright FRIDGE (2004) Page 131

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