Providing the ‘magic’ element in fragrances

Today, approximately 5,000 different aroma chemicals are available on the market including synthetic and natural products. These compounds are the fundamental basis from which are created fragrances (= perfume oils) and flavours for non-food and food or oral care applications, respectively. With a few historical exceptions only natural or natureidentical aroma chemicals (EU definition) are utilised for flavour creations,1 while all toxicologically safe compounds2 can be used in fragrances, if they are registered according to relevant chemical legislation and in due course to REACH.3 This article will focus only on aroma chemicals used in perfumery. Provided will be insights into aroma chemicals and their importance to create the magic smell in fragrances.

Origin and classification of aroma chemicals

The majority of aroma chemicals are obtained today through chemical synthesis, but natural raw materials still play an important role in the perfumer’s palette.4 Natural raw materials are today mainly derived from plants. Animal derived products are substituted in modern perfumery through synthetic equivalents to support the protection of species and therefore are mentioned here only for historic reasons. Gland secretions from civet cats (Civettictis civetta and Viverra zibetha), musk deers (Moschus moschiferus) and beavers (Castor fiber), were once used to obtain civet, musk and castoreum, respectively. Also a metabolic product from sperm whales (Physeter catodon) called ambergris or ambra when processed could be found in the ancient perfumer’s pallet. While products from mammals are no longer in use, one inexhaustible metabolic product from an insect, beeswax from honey bees (Apris mellifera), is still processed to manufacture beeswax absolute. Approximately 250 plant species are used to produce more than 500 different natural products. They are obtained from various plant parts such as flowers, fruits, peels, leaves, barks, seeds, woods, roots, and also resinous exudates by either distillation, mechanical separation (“pressing”) or extraction with various solvents including supercritical CO2. Products produced via steam / water distillation or cold pressing are by definition called essential oils. Solvent extracts are either called concretes or resinoids. The latter are obtained from plant exudates with solvents such as ethanol, methanol etc, while concretes are extracted from various plant parts with non-polar solvents (hexane, petroleum ether, toluene etc). Concretes are rarely used in perfumery due to solubility issues. However, the corresponding wax-free absolutes are highly appreciated natural raw materials in perfumery. For this purpose the concrete is taken up in ethanol, cooled, filtered and the filtrate is concentrated under reduced pressure to obtain delicate smelling absolutes. Composition and consequential odour of natural products is influenced by external factors such as place of origin, temperature, rain and soil. Furthermore, these external factors can also affect price and availability. Aroma chemicals obtained by industrial synthesis are more predictable in terms of composition, odour, price and availability. Slight variations in odour profile can be the result of different manufacturing processes and distillation capabilities. Synthetic aroma chemicals can be grouped into three classes: commodities, specialties and captives (Table 1). Captives are considered the most important compounds of the individual fragrance houses due to the fact that they are only available to the manufacturer and protected by patents (Fig. 1). Dominant players in this field are Symrise, Firmenich, Givaudan, IFF and Takasago. Captives can give fragrances the distinctive note, which makes them impossible to copy. Captives can be also classified as captive specialties. Specialties are sometimes also linked to a unique manufacturing process or technology, which limits the amount of producers to a few or only one. Such specialties or processes often also enjoy patent protection. Commodities on the other hand are normally produced in bulk quantities and were introduced to the market usually years ago and therefore no longer have patent coverage. Today commodities are often produced in China and India due to price pressure. Despite the large amount of existing aroma chemicals, the search for, and synthesis of, new outstanding molecules are still integral parts of fragrance and flavour research.