Industrial Fragrance Chemistry: A Brief Historical Perspective

Industrial Fragrance Chemistry: A Brief Historical Perspective

Authors: Olivier R.P. David and Franco Doro

  1. Introduction
  2. The Rise of Synthetic Fragrance Ingredients (1870/1910)
  3. “Sell by Smell” (1920-1940)
  4. Fragrance Ingredients ‘Blockbusters’ (1950-1970)
  5. Focus on odor potency (1980-2000)
  6. Fragrance Delivery Systems & Back to Nature (2000-2020)
  7. Conclusion and Outlook


Perfumery has evolved from a handcraft activity, marking supreme aristocratic luxury in the Renaissance, to a global industry powering scent experiences for present-day consumers through the use of a myriad of consumer packaged goods. This contribution reviews major breakthroughs in the field, including landmark fragrance ingredients, technological advances in scent delivery, and key innovations in consumer products which created the demand for scientific and technological advancements in the scent domain. These innovations are presented chronologically, relying solely on information drawn from public written sources, spanning a time period of 150 years (1870-2020). We hope with this contribution to generate interest in the readership for this fascinating field, while celebrating 150 years of innovation for scented mass-market products..

1. Introduction

Scent is ubiquitous in our life as consumers. We experience scents through the multiple consumer products used in our daily routines, from personal hygiene products such as soaps and shampoo to household products ranging from all-purpose cleaners to fabric detergents.

For most of the pre-industrial area, as far back as 3000 BC,[1] fragrances were already incorporated in products such as unguents, candles and soaps. Their consumption was, however, limited to the elites of the time. It was already known in ancient times that scent could enhance mood and physical healing, making it an integral part of public rituals and healing practices. Fast forward to modern times and the psycho-physiological effects of scent are being used for more profane purposes to enhance the overall consumer experience of many products. Scent has become a powerful factor in determining consumer appeal and conveying emotional and efficacy cues for various brands on a commercial scale.

The use of scented products had not changed dramatically up to the second half of the 19th century. Since then, fragrances have been increasingly used across a wide range of products for a growing segment of the population. The mass-production of consumer goods in the household and personal hygiene space that started in the first half of the 20th century brought an explosion of scent experience to the ordinary consumers that is still in full swing today.

The primary catalyst for the increasing incorporation of scent into consumer products has been the cost optimization of synthetic fragrance ingredients. As a result, fragrances can be extensively utilized in the creation of new consumer products, as well as in the expansion into new olfactory domains for existing

scented consumer products. This resultant increase in supply and demand has been pivotal in the growth of this market segment.

The global household goods market (including laundry products) was worth USD 177.43 billion in 2021 and is projected to grow at 6.8% CAGR from 2022-2030.[2] Similarly, the global personal hygiene and grooming market was valued at USD 482.8 billion in 2021 and is expected to grow at 7.7% CAGR from 2022- 2030.[3] The combined market size of household and personal hygiene goods is approximately equivalent to the GDP generated in 2022 by a country like Austria.[4]

In this review, we will outline what we consider to be the crucial scientific and technological breakthroughs in the field of scent that have had a lasting impact on product development strategies in consumer packaged goods industry, with a focus on the household- and personal hygiene/grooming segments, as well as the reciprocal influence of the latter on the field of scent. We recognize the major influence that fine fragrances (or perfumes) have played in the expansion of scent across consumer products. With this in mind, we will report some of the key historical milestones in fine fragrance development that have had a trickle-down effect on other consumer products.[5] This review is conceived to give a flavor (or should we say a scent) of the intertwined relation between scent and consumer packaged goods in the course of the last 150 years. We aim as well to stimulate the specialized readership to contribute to the collection of scattered information and thus help the authors to continue carrying out the historical documentation of this fascinating field in future articles.

2. The Rise of Synthetic Fragrance Ingredients (1870/1910)
Figure 1. Timeline of the most important synthetic ingredients, according to the date of first academic synthesis or patent priority date for 1850-1910.
Figure 1. Timeline of the most important synthetic ingredients, according to the date of first academic synthesis or patent priority date for 1850-1910.

The burgeoning of modern perfumery can be symbolically dated to 1874 with the foundation of Haarmann & Reimer, the first company devoted to the production of synthetic ingredients for flavors and perfumes.[6] Other actors quickly joined the field to propose novel synthetic ingredients, most of them being specialists in essential oils and natural extracts that extended their offer to pure molecules. In Table 1, we report the main companies operating in synthetic ingredients at the end of the 19th century. Several of these pioneering companies merged with other ones to form some of the global fragrance companies operating today.

Essential oils were the dominant fragrance materials till the late 1800s, but their use was heavily limited by their high price and limited/unstable supply. With the entrance to the market of Haarmann & Reimer and of Fabriques de Laire, several fragrance materials were made available to perfumers through chemical synthesis by the end of the 19th century, see Figure 1.[7] Synthetic fragrance ingredients which made their entry into the palette of perfumers were: vanillin 1 (Haarmann and Tiemann, 1874) which initial profitable industrial success boosted subsequent investments in the field; coumarin 2 (1876) unlocking abstraction in fragrances by enabling the creation of Fougere perfumes with its smell of hay; nitro musks 3a-d (Baur, 1888),[8] which opened new opportunities as a ‘fixateur’ for fragrances; ionones 4a and methyl ionones 4b (Tiemann, 1893),[9] with which the much appreciated violet smell could be recreated; methyl anthranilate 5 (Erdmann brothers, 1898) isolated in neroli oil; aliphatic aldehydes 6 (C12 MNA 6a Darzens, ~1903), a series of molecules with fresh-soapy smells, critical for creating Chanel N°5; isobutyl quinoline or ‘IBQ’ 7 (Darzens, 1908), with a unique smell that evokes leather; hydroxycitronellal 8 (1905),[10] triggering the creativity of perfumers to reproduce the transparent, spring poetry of lily-ofthe-valley. Interestingly, the first molecules were rationally discovered through screening of odorous principles isolated from natural materials, while the last two were discovered by serendipity during academic investigations. Although such molecules were fairly expensive at their respective launches, even more than their natural counterparts sometimes, production optimization led to drastic cost reductions allowing for their inclusion in consumer packaged goods. Eugene Charabot, a big name in the trade, noted in his 1900 book on ‘Artificial Perfumes’[11] that vanillin was initially sold at 8750 fr/kg in 1876, to decrease to 938 fr/kg in 1885, and less than 115 fr/kg in 1900, while natural vanilla was sold at 350 fr/kg in 1823 or 40-50 fr/kg in 1909. This is even more dramatic with heliotropin 9 that dropped from 3790 fr/kg in 1876 to 37,5 fr/kg in 1899, a price divided by 100.

Click to learn the full tables.

One should not forget the persisting role of natural ingredients in the perfumer’s palette even while it is constantly extended by chemists. A novel mode of concentration of odorous principles was introduced by Etablissements Antoine Chiris in the late 1890’s with the first flower absolutes obtained by extraction with volatile solvents (diethyl ether, petroleum ether, liquified butane) immediately followed by Robertet and Lautier. This was crucial because important odorous principles were still inaccessible to chemical reproduction. Oakmoss, vetiver and patchouli, were far too complex for the analytical techniques of the time to allow identification of key odorants, or even if deciphered, the molecules were far too intricate to be duplicated by synthesis. Patchouli oil, for example, passed from being introduced in perfumery in the mid 19th century to become one of the most important fragrance ingredients only a few decades later during the Belle Epoque (late 1890’s) and it was considered indispensable for the creation of chypre notes in reports dated in the 1920’s.[12] Patchoulol 10, first named ‘patchouli camphor’,

was isolated in 1869 by M. H. Gal,[13] but the genuine tricyclic structure was deciphered only in 1963 by Jack D. Dunitz and George Büchi,[14] the latter describing the formal total synthesis one year later.[15]

The first consumer products containing fragrances of broad appeal to ordinary consumers were in fact soaps. In the 1910s there were already clear olfactory directions for soaps, though limited to the most affordable and also chemically stable ingredients. Hence, preferred scents were bitter almond (benzaldehyde 11), rose (phenyl ethyl alcohol 12), violet (ionones 4), heliotrope (piperonal/heliotropin 9), lilac (terpineol 13) or carnation (eugenol from clove 14).[17] Notably, terpineol 13 was considered one of the most important fragrance ingredients for soaps well into the 1950s.

A key event which defined how we experience fine fragrances today happened with the industrial production of atomizers in both Europe and the US from the early 1900s onwards. An atomizer is a device that allows for delivery of a fragrance in a spray of tiny droplets. This device started to be produced by artisans in the second half of the 19th century and we have a record of such a device being showcased at the Paris World Expo of 1878.[18] Marcel Frank et cie (Paris) was one of the companies most active in this area in the first decades of the 20th century.

In the US, Dr. Allen De Vilbiss and his sons designed and manufactured atomizers for the perfumery industry around the same time. These devices were based on pre-existing prototypes used by otolaryngologists, see Figure 3.[20] The advent of atomizers revolutionized consumer relationships with fragrances, making them more convenient and safer, thereby democratizing the perfuming gesture. Prior to their introduction, fragrances were enjoyed by infusing or sprinkling a cloth with a perfume or by applying a drop of perfume to the wrist and rubbing it in.[21] This paradigm shift was reported by the specialized press in these terms “There is almost as much difference between the application of perfume with cotton-wool or the corner of a towel and with the perfume spray as there is between the sensation of water thrown at the face and that of softly dropping rain. The first is a shock—the second is soothing and refreshing.”[18] The use of atomizers popularized sprays as a new delivery system for fragrances, which eventually led to the development of pressurized air fresheners and deodorant sprays in the following decades.

3. “Sell by Smell” (1920-1940)

The interwar period saw massive progress in analytical chemistry and the first spectacular successes in the total synthesis of natural products. Chemistry reached a maturity that allowed reproduction of major odorant principles. Chemistry was hence at the center of ingredient innovation from the start, while diffusion technologies defined a second axis of innovation. A major breakthrough was the comprehension by Leopold Ruzicka of the macrocyclic nature of musk and civet odorants. He would receive the Nobel prize (1939) for this discovery and his contribution to terpene chemistry (syntheses of fenchone 15, linalool 16, farnesol 17, nerolidol 18).[22] Consequently, this was the golden age for synthetic musks with the synthesis of several macrocyclic musks (exaltone 19, civettone 20, exaltolide 21, Globanone 22, muscone 23, ambrettolide 24) 1924-34 by Ruzicka and colleagues; Musk T by Wallace H. Carothers (first sold as Astrotone 25) 1933 during a side-project devoted to Polyesters, having previously invented no less than Neoprene and Nylon.

Chemical processes for established synthetic ingredients were re-designed to obtain more economically viable routes to support the expanding need of the consumer goods industry. For example, whilst some ingredients could be synthesized for the first time in the late 19th century, such as phenyl ethyl alcohol 12 (Radziszewski, 1876), these first synthetic attempts involved either tedious synthesis or yielded a poor olfactory profile with impurities that required laborious chemical separations. In the post WWI years new chemical technologies were employed for the first time to obtain fragrance ingredients more economically through higher yields. Hence, in the early 1930’s, a new phenyl ethyl alcohol quality was synthesized via a Friedel-Crafts reaction between ethylene oxide and benzene.[23]

By the late thirties, chemists were thought to have almost completely reproduced, synthetically, the key components of essential oils known at the time. Jasmone 26 (Treff, 1935) and alpha-irone 27 (Naves, 1943) were considered the latest key natural components to be reproduced synthetically on a commercial scale, see Figure 4. Synthetic chemists of the time had to go for inspiration outside of nature and this enabled the discovery of some exceptional fragrance ingredients that brought perfumery to new heights as will be witnessed in the post WWII era.[24]

In this era the potential of synthetics was clearly established, with increasing advertising activity in specialized magazines for the replacement (or complement use) of natural oils. Fragrances were reported in advertisements as the cheapest form of product promotion and industry leaders had adopted the slogan “sell by smell”.[25]

Figure 4. Timeline of the most important synthetic ingredients
Figure 4. Timeline of the most important synthetic ingredients, according to the date of first synthesis or patent priority date for 1910-1940. Pictures of prominent
chemists active in the 1910-1940 period. Photo of Leopold Ruzicka: copyright-free from ETH Bildarchiv, see ref. [26a]. Photo of Yves-René Naves: copyright-free
from “Le nouvelliste, 22 septembre 1951” retrieved at see ref. [26b]. Photo of Wallace H. Carothers: copyright-free from Commons
Wikipedia see ref. [26c].

In the 20’-30’s of the last century several technical accounts were published on how to introduce fragrances into toiletries. These technical reports share guidelines for incorporating fragrances into face powders, body lotions, soaps,[27] bath salts, shampoo or depilatory creams.[28] Regarding fragrances in shampoo, the literature of the time reports that there were no established olfactory directions yet. It seems that the first scented liquid shampoo (invented in 1927) had a violet smell, which most likely derived from scents already used in powder shampoos (the precursor of liquid shampoos).

It is likely that around the early 40’s the first olfactory directions were established for some of the upcoming branded shampoos we know today.[29] The initial benefit of shampoos was to cleanse hair from excess fats. These products would be the focus of continuous innovation in the upcoming decades (and to this date) to ensure in addition to cleaning the delivery of additional features such as optimal foaming upon use, rinse, rheology control of formulation, skin mildness or deposition of actives. The field of formulation science and ingredient performance played a crucial role in these advancements. For instance, synthetic, negatively-charged surfactants were introduced in the 1930s to replace fat-based soaps. This led, in the coming decades, to opportunities for improved fragrance delivery to the skin and hair. One notable example is the use of cationic polymers in shampoo formulation, which induce the formation of coacervates upon dilution during the rinse of shampoo with water, which aids in fragrance deposition. These developments broadened the range of available scents, allowing for the effective communication of desired beauty benefits and efficacy cues.[30]

Odorono (1912) seems to have been the first antiperspirant of wide distribution. It is unclear when scent was first introduced in antiperspirants and deodorants. The earliest source we could retrieve relates to advertisements from the 1950s.[31] Most advertisements referred to fresh and sweet scents, but we could not find more detailed sources related to the specific fragrance ingredients. The sale of antiperspirants increased 600% between the early 1940s and the late 1950s.[32] We could speculate that scent played some role in the popularization of this personal care item around this time span.

The birth of scented pressurized air freshener products could be identified in the post WWII years. At that time it was common to come across the word “space deodorants”. Aerosols were introduced as “bug bombs” to dispense insecticide from pressurized cans during WWII. Typical propellants were chlorofluorocarbons (CFCs), which due to their low cost in combination with economical packaging gave a start to scented air freshener products as new product lines in the post-WWII years. Formulation chemists had already developed clear guidelines in the 1940s on how to create fragrances in these new matrices, taking into account the solubility of fragrance ingredients in solvents and using co-solvents for optimal solubility.[33] Fluorinated propellants started to be replaced in the 1980s (and well into the 1990s) with light alkanes such as propane, butane and isobutane which have less impact on the atmosphere.[34]

4. Fragrance Ingredients ‘Blockbusters’ (1950-1970)

WWII brought a brutal stop to research programs directed towards products for ‘frivolities’ such as perfumes and luxury soaps, but the postwar period gathered the fruits of the investigations undertaken in the 1930s. Moreover, systematic studies were launched during the 1950s to explore the olfactory diversity offered by synthetic molecules randomly prepared from abundant terpenes after application of well-controlled synthetic processes. The main feedstock of terpenes is gum turpentine and crude sulfate turpentine, the latter a by-product from the pine wood pulping industry. Terpene chemistry had its origin in the late 1800s but the full modus operandi of nature in the biosynthesis of these ingredients was revealed only in the late 1940/50s. The presence of multiple isoprene units in terpenoids was observed first by Wallach (1887, Nobel Prize winner in 1910) and established as a general principle by Ruzicka in the “isoprene rule”. The mechanistic explanation for this rule was established as a result of significant advancements in the field of biochemistry. The pioneering work of Bloch and Lynen, who were awarded the Nobel Prize in Medicine in 1964, played a crucial role in generating the key evidence to define the mevalonate pathway for the synthesis of terpenes in nature.[35]

We could retrieve a dialogue from the early 1950’s by Gerrit Jan Beets, a prominent fragrance chemist of the time and biochemist Arie Haagen-Smit on the origin of terpenoid ingredients and biogenesis. Beets speculated, erroneously, that terpenoid ingredients were formed in nature by chemical reaction of small chemical molecules (such as formaldehyde and acrolein) which reacted by means of the Prins-reaction (named after Hendrik Prins, another prominent fragrance chemist)[36] and aldol condensation. This theory was considered unlikely by Haagen-Smit, as there was already evidence of the role of phosphorylated intermediates for the formation of terpenes in nature through enzyme-mediated reactions.[37] We could see in these early discoveries and dialogues the first seeds of the role biochemistry would play in the fragrance industry: first in explaining natural phenomena and in the future as a technology tool. It would still take another 60 years for the fragrance industry to commercially produce the first biotech-based perfumery ingredients.[38]

Terpenes were submitted by chemists to a large array of chemical transformations in order to produce a vast molecular diversity of synthetic molecules into which “hits” were selected for their olfactory appeal. This somewhat brutal “try-and-smell” approach however led to an impressive number of discoveries with the patenting of an unprecedented palette of artificial ingredients. Prominent examples are: dihydromyrcenol 28 displaying a diffusive lavender-like freshness (Webb, 1956); Lyral 29, derived from myrcenol, conveying a clean lily-of-thevalley impression (Steinbach, 1958); Cedramber 30, prepared from cedrene, with a dry, powerful smell of amber and wood (Blumenthal, 1966); Iso E super 31, made in two steps from myrcene, bringing a complex and rich impression of cedar, of vetiver with mineral and ambery facets (Hall, 1973); Sandalore 32, the first artificial molecule derived from pinene with a strong sandalwood smell (Naipawer, 1976).

Of course, robust aromatic chemistry based on petrochemical raw materials was more than ever productive, using the more subtle “small variation” approach by exploring a molecular domain around a known odorant. This was actually rationalized with the concept of structure-activity relationship and the birth of manifold olfactory models supposed to capture the molecular essence of lily-of-the-valley, sandalwood, amber, musk, etc.[39]

Although only vaguely predictive, this methodology brought us many splendid ingredients: Helional 33, with watery, melon-like smell (Beets, 1958); Lilial 34, among the most powerful odorants reproducing lily-of-the-valley (Carpenter, 1956); Bourgeonal 35, again conveying a lily-of-the-valley impression with greener facets (Dorsky, 1959). A series of polycyclic musks were synthesized and launched: Phantolid 36 (Fuchs, 1951), Versalide 37 (Carpenter, 1953), Celestolide 38 (Beets, 1955), culminating with Galaxolide 39 (Beets, 1962).[41] The valorization of a precursor of the latter brought us the perfumery platypus Cashmeran 40, smelling all at once woody, mineral, musky, slightly fruity and balsamic (Hall, 1969).We should not forget the serendipitous popping of marine odorants with the preparation of several oxygenated derivatives of anxiolytic benzodiazepines by the Pfizer team, resulting in Calone 1951 41 (Beereboom, 1966) all smelling watermelon with an oceanic feel.

Then, scrupulous scrutiny of expensive natural ingredients fished out trace molecules that became extremely interesting high impact odorants, Ambrox 42 with a soft and dry smell of ambergris (Stoll, 1951); Rose oxide 43, bringing the green, sharp, metallic facets of fresh roses (Stoll, 1961); damascones 44a-c important for the fruity, marmalade-like notes of roses (Demole, 1967); or slightly modified structures such as Hedione 45, a hydrogenated version of methyl jasmonate present in jasmine, with a luminous, transparent and blooming smell (Demole, 1960); ethyl maltol 46 with its characteristic scent of candy floss (Stephen, 1963); Muscenone 47, an intermediary molecule in the synthesis of muscone 23, but with a stronger soft-musky impression (Becker, 1967).

Cleansing and scenting of every aspect of domestic life, with increasing frequency, became the norm, further strengthening the professional subdivisions of the consumer goods market with specifically devoted household and personal hygiene/grooming product segments, each sub-specialized in laundry, dishwashing and house cleaning for the former, and soap, shampoo, grooming and deodorants for the latter. Cable television became a mass-media promoting consumer product brands to viewers, strongly influencing their purchasing choices and driving demand for olfactory differentiation.

Currently, a major share of fragrances manufactured globally serves the laundry market. The use of scent in laundry products first emerged in the early 1950s and has since experienced rapid growth, coinciding with the mass production of laundry products and the widespread adoption of washing machines. Synthetic surfactants like alkyl sulfates emerged in the 1930s, proving superior to fat-based soaps at cleaning in hard water. They were instrumental in the growth of the laundry product industry.

In the history of Tide, Rafael Trujillo describes the evolution journey of the scent of Tide which became the quintessential smell of clean for American consumers. A relatively simple smell based on a rose note (used merely to cover the off odors of the first synthetic detergents) developed over time into the very sophisticated scent we know today.[42]

In the late 1960s musk ingredients were already used cumulatively above 20%w/w in fragrances across both detergents and fabric conditioners. Galaxolide 39 alone is reported to be used above 20%w/w in some laundry products.[43] Musk ingredients were responsible for the post-wash scent’s tenacity on clothes, playing in this sense a technology role that would be taken over by fragrance encapsulation systems in the 2000s.

The first citrus-scented liquid dish soaps were introduced, to the best of our knowledge, in the late 1960s.[44] Citrus smell is arguably the main olfactory direction for the dishwashing category, that would grow to encompass automatic dishwasher tablets. Pine was the dominant smell for all-purpose cleaners from their introduction in the late 1920s and we had to wait until the 1970s to start seeing the first examples of diversification into other olfactory realms.[45] Pine was associated with the smell of a clean house so strongly that it seems only in the 1980s that there was a clear shift into other olfactory directions.[46] The perpetually sought after freshness was given a new expansion thanks to dihydromyrcenol 28, first prepared in 1956, but whose use was boosted by a 1966 patent,[47] unlocking the production of olfactory pure material allowing for use in large proportions in both fine and functional perfumery.

Revolutions are not always primarily directed towards the consumer. Several analytical techniques for the characterization of fragrance molecules were developed and introduced, starting from the 1950s, in both academia and fragrance houses, see Figure 6. The emergence of nuclear magnetic resonance (NMR) as an analytical technique occurred in the late 1950s. While existing analytical techniques such as IR and UV spectroscopy provide information about the nature of functional groups of organic molecules, 1H-NMR spectra from first commercial NMR spectrometers (30-60 MHz) supported the elucidation of the structure and the stereochemistry of individual hydrogen and carbon atoms. George Büchi, a former student of Ruzicka, was among the pioneers in using this technique for elucidating the structure of natural products, particularly sesquiterpenes like patchoulol[15]. The advancement of NMR in the subsequent decades would be significantly driven by the aspiration of chemists to solve the intricate structures of complex natural products. First chromatography systems were available in the early 1970s and the decade saw the exponential increase of molecule identification libraries.[48] This dramatically expanded the knowledge about odorants in natural sources, allowing for the identification of low concentration, that is high impact, molecules. In this regard the 1970 discovery of damascenone in Damas rose oil perfectly epitomizes this progress with the crucial
contribution of Ervin sz. Kováts.[50]

These tools gave a new dimension to quality control, with precise quantification performed on all goods, from raw material to finished products, aligning safety standards to the emerging regulations for humans, animals and the environment. The Research Institute for Fragrance Materials (RIFM) started its work on safety assessment of fragrances in 1966, operative regulation being then implemented by The International Fragrance Association (IFRA) from 1973 on. Thirdly, chromatographic methods opened the possibility of ‘deformulation’ with the deciphering of any perfume composition, allowing for a tight technological watch of competitors and thus largely uncovering the secrecy historically associated with fragrance compounding.

5. Focus on odor potency (1980-2000)

Two oil crises (1973 & 1979) steeply impeded research programs; with an impressive flattening in the number of patents in the field, resulting in the absence of any new blockbuster in the 1980s, rather distinctive ingredients enriched the palette by varying known structures, see Figure 7. Installed hygiene habits were comforted and efficacy parameters of scented products like diffusion and tenacity were aligned with the societal trends of these decades valorizing performance and self-confidence. Nonetheless, important new olfactory trends were pushed in the musk direction with Helvetolide 48a (Giersch, 1990) the first member of the novel alicyclic family of musks 48a-f, or the ambery/dry woods 49 setting a trend to become massively important, with Ambrocenide 49f (Pickenhagen, 1997). Thus, beyond extensions of known olfactory territories like synthetic ambers 49, sandalwoods 50 or muguets 51, the main additions to the palette were fruity and green notes such as: Undecavertol 52, with a fatty-green smell (Kaiser, 1981); Methyl pamplemousse 53, having pink grapefruit notes (Gebauer, 1983); Cassifix 54, with a sparkling, green note of cassis (Narula, 1990).[51]

More generally, the period saw the systematization of the ‘captive’ commercial practice. A newly patented ingredient was solely proposed to perfumers within the company, without sales to competitors, in order to benefit from a distinctive olfactory advantage to answer specific needs of clients, at least for a period of time. Although punctually done in the past, with Ionone De Laire 4a used by Roger & Gallet for Vera Violetta, or pure Hedione 45 for Eau Sauvage by Christian Dior, this concept was henceforth almost universally applied to novel introductions. Scented care rituals were by then well implanted within the population, pretty equally all over the planet with the massive globalization of occidental habits and trademarks. New commercial circuits deeply influenced consumption habits, ‘selective perfumery’ distribution networks with items presented in the same manner as goods on supermarket shelves revolutionized our relationship to fine fragrance. Purchase decisions in this context are based on first impressions, emphasizing the pleasantness of the top notes, which hence must be shaped in a catchy way. The global societal atmosphere of the 1980s put a strong emphasis on the ideas of performance, self-confidence and self-promotion, so the overall appreciation of a fragrance then mostly relied on the strength of diffusion, the tenacity and the distinctive character of the sillage.

This influenced perfumers in favoring high impact odorants and led them to structure their compositions on solid foundations, as offered by modern musks like Galaxolide 39, working the woody aspects around Iso E Super 31 and the floral theme around methyl ionones 4b, while Hedione 45 and Lilial 34 were perfect to bring diffusion and bloom, finally powerful and distinctive captives gave memorable character. This modern formulation style is epitomized by the work of Sophie Grojsman with Trésor for Lancôme built around a Hedione/methyl ionone/Iso E Super/Galaxolide heart (the so called ‘hug me’ accord with 20% each) and then touches of floral and fruity notes to give the unique appeal. Hedione,[52] methyl ionones, Iso e super[53] and Musk T are nearly perfect ingredients, as they are powerful, stable, usable in many scent theme, and if we add their relative low cost when patents reached the public domain, ideal building blocks for ubiquitous utilization across household and personal hygiene/grooming products.

At the turn of the 80-90’s decades, an anxious atmosphere developed with the confluence of the Gulf war, AIDS pandemic and first awareness of environmental problems, shifting olfactory preferences to scents evoking cleanness, purification and comfort. Hence, marine, ozonic notes such as Calone 1951 41 found widespread uses. One of the most prominent example is Сalvin Klein Escape (1991) which contains 0.8%w/w of Calone 1951.[56] Sea-breeze like smells started successively a major trend in air fresheners and surface cleaners in the 1990s.

Chemists invented and established at scale new synthetic tools for preparing fragrance molecules efficiently, with special attention paid to be nature identical as for chirality.[57] The most important example is the asymmetric synthesis of L-(-)-menthol 55, at industrial scale, developed in the 1980s.[58] Noyori would receive the Nobel prize in chemistry in 2001 for his contribution to metal-catalyzed asymmetric synthesis. Menthol can be prepared in two mirror forms D and L (stereoisomers), the latter is however the most potent for inducing a cooling effect in humans as L-menthol interacts with the trigeminal system.[59]

Several other molecules would be prepared in the coming decades,[60] through the use of this technology (citronellal 56, isopulegol 57) or others, like Paradisone 58, a highly enantioenriched version of Hedione 45 developed using an asymmetric hydrogenation transformation patented in 1997.[61] Cyclopropanation is a chemical transformation that has entered the toolbox of fragrance chemists in the late 1990s. A prominent example is Javanol 50d, derived from optically active alphapinene. Interestingly, the Javanol isomer with a cis configuration between the cyclopropane at the cyclopentane ring and the side chain is reported to be tenfold weaker from an olfactory standpoint. [62]

As gas-chromatography was a well established technique for the analysis of fragrance ingredients, analytical chemists refined it, with the introduction of headspace analysis, to capture the scented air surrounding living plants.[63] Dr. Roman Kaiser was a prominent figure in developing headspace techniques, elucidating numerous compositions of floral scents, thus helping in the reproduction of fresh impressions of them.

6. Fragrance Delivery Systems & Back to Nature (2000-2020)

For more than a century, chemistry enabled ingredient manufacturers to synthesize natural and artificial molecules, producing them at scale through efficient and selective chemical processes, a seemingly permanent move away from nature. This was reversed in the 2000s with strong environmental concerns from consumers, together with geopolitical instabilities leading to limitations of supply of essential oils employed as reactants. Solutions came from biology, biochemistry and biotechnology, providing the processing tools to prepare fragrance ingredients, and Nature, once again, being the inspiration source. Fragrance ingredients produced biotechnologically[64] today are: Patchouli-scented Clearwood 59 (arguably the first ingredient launched in the industry, 2014);[65] biosynthetic santalol, Dreamwood 60 (launched in 2020); woody-ambery with Ambrox Super 61 (launched 2016) and Amberketal 62 or Z11 (a nonnatural ingredient biosynthetically made, launched in 2018); nootkatone 63, present in grapefruit or vetiver and important to shape nice citrus notes, can be made by biochemical oxidation of valencene 64, itself made by fermentation of glucose with bacteria.[66] Ongoing research programs were successful in biosynthesizing more and more diverse molecules, (R)-muscone 23 (musk note in musk grain), cis-hexenol 65 (green note of cut grass), furaneol 66 (caramelic), Frambinone 67 (raspberry), are now waiting for commercial production, see Figure 8.[67]

Akigalawood 68 (an ingredient rich in nature-identical rotundone), is not produced via biosynthesis per se, but relies on enzymatic oxidation of upcycled terpenic fractions of natural patchouli oil, thus considered a hemi-biosynthesis of rotundone (patented in 2012).

Since 2000 we have witnessed an explosion of new fragrance ingredients launched across all olfactory camps. Whilst this last generation of fragrance ingredients does not seem to offer the broad application of more established ingredients such as Iso E Super, Hedione, they do provide the desired differentiation to enable perfumers to create more sophisticated fragrances.

New product developments in the 2000s, such as scent boosters and laundry pods, gave new possibilities to perfumers to expand the olfactory territories in laundry products, as the scent could be compartmentalized and thus insulated from aggressive ingredients and oxygen through formulation and packaging solutions.

Since the 1970s, it has been recognized that fragrance ingredients alone cannot deliver a long-lasting scent for wash-off applications such as laundry products on dry clothes. Patent applications in the late 1970s and early 1980s described the first fragrance delivery systems using wax, gelatin, gum acacia, and urea-formaldehyde resins to trap the fragrance oil.[68] However, to the best of our knowledge, the commercial use of these technologies in major consumer brands took place only in the 2000s.[69] Up to 2020, synthetic polymers such as melamine-formaldehyde or poly(methyl methacrylate) have been among the most used materials for fragrance encapsulation.[70] Fragrance-containing encapsulates in consumer products typically have a diameter ranging from 10μm to 50μm and a wall thickness below 1μm, see Figure 9.[71]

Figure 9. Schematic representation of trigger-activated release of fragrances
Figure 9. Schematic representation of trigger-activated release of fragrances
through a) microencapsualtion, b) profragrances, R (organic scaffolds such as
carboxylate,glucosidecarbonate, imines, unsaturated alcohols).

The upcoming ban on microplastics in Europe has prompted the industry to develop more sustainable alternatives to current encapsulation systems. Numerous companies, several without a core focus on fragrance, have entered the market in recent years, as evidenced by several patent filings and marketing activities. Today, fragrance encapsulation systems are mainly used for laundry products. The most prominent example is in fabric conditioners which contain typically both a scent in the form of oil dispersed in the product formulation, to deliver the “out-of-the-bottle” initial smell, and an encapsulated fragrance oil to ensure the scent is delivered to the dry laundry upon use.

Pro-fragrances are delivery technologies which release selectively only one fragrance material upon activation of a chemical or physical trigger such as pH change, temperature, light exposure, physical friction or a combination thereof. The commercialization of this technology predates the more established encapsulation technology as it was introduced in the industry in the mid 1990s.[72] The first established example is digeranyl succinate incorporated in fabric conditioners, which releases geraniol upon reaction with lipases originating from detergents and still present in the wash liquor during the rinsing cycle. These technologies are typically miscible with a fragrance oil, which can simplify the manufacturing and supply chain process, and can be good replacements to microcapsules where the latter is not compatible with the product formulation.[73]

7. Conclusion and Outlook

Over the past 150 years, the fragrance industry has experienced a continuous interplay of scientific discoveries and innovation which enabled the creation of a multi-billion industry. This has encompassed advances in new molecule discovery, characterization techniques, manufacturing processes, and fragrance controlled release technologies.[55]

This progress has been fueled by the development and diversification of consumer goods, accompanied by the utilization of novel formulation and packaging materials, presenting scientists in the fragrance industry with an ever-expanding arena of challenges and opportunities.

Historically, research and innovation in the realm of scent and consumer goods have relied, to some extent, on empirical approaches. Some of the greatest inventions in the field are owed to sheer serendipity. We believe serendipity will keep playing an important role in the future, as perfumery embodies both artistry and science. We are currently witnessing a growing integration of artificial intelligence (AI) into very diverse aspects of scent innovation, such as new molecule discovery, raw material procurement, and consumer understanding.

Looking ahead, we anticipate that societal demands for a better sustainable footprint of consumer products, the integration of digital technologies into our homes, lives, and product usage, and the rise of e-commerce will provide fresh impetus for innovation in the scent industry. These factors will drive the utilization of materials with an enhanced sustainability/circularity profile and the creation of novel products and services for household and personal hygiene/grooming segments, with scent playing a central role in enhancing consumer experiences.

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