Fragrancing Part 3: synthetic vs natural and aroma types

What’s the difference between synthetic and natural fragrances? What kind of fragrances are out there? These are two questions I get all the time in our workshops. Is natural always better? Why would we ever use synthetic notes? In this blog post, part 3 of our fragrancing series, I’ll take you through these questions and more so you’ll have a better understanding of fragrancing notes and the many options out there! Enjoy!

 

Natural VS Synthetic Aromas


In general, synthetic notes can be A LOT more simple than a natural aroma. When we talk about ‘synthetic’ in the cosmetic industry, what we often mean is the materials are derived from petrochemicals. Way back when, we got really good at extracting and refining petroleum into many different materials that today we rely on heavily, for example in many pharmaceuticals, packaging and plastics, and many cosmetic ingredients. Because of the chemistry of petroleum, compared to other starting materials, it’s incredibly easy to manipulate and we’ve gotten really good at doing so, hence its popularity. With synthetic notes, you can get single notes, for example, aldehyde, the characteristic note in Chanel No 5. In contrast, natural aromas are much more complex and naturally contain hundreds of aromatic chemicals.


I find thinking of accords are great ways of understanding this. An accord is essentially just a bunch of different chemicals working together to give you x aroma. For example, musks, amber, fruit (e.g. strawberry); these are blends of many synthetic notes to capture these scents. With synthetic notes, they’re often single notes, or you can put them together and create an accord. With natural notes, for example, an essential oil, these can really be thought of an accord from the get-go. Lemon essential oil, for example, can be made up of a-pinene, camphene, b-pinene, sabinene, linalool, limonene, nerol, and many other chemical components. Alone, they would not smell like a lemon, but together, that’s where the magic starts to happen! Many of these components can also be synthetic, e.g. nerol maybe. The huge benefit in perfumery of having these single notes is that you can create unique smells that would not be possible with natural aromas, fruity smells are a great example of that.

 

There’s an incredible amount of misinformation about fragrances. I always hear people saying that synthetic fragrances are way more allergenic than natural ones and that natural fragrances are always the eco option. Simply put, it’s not that cut and dry. Clearly, when we’re talking about sustainability, petrol-derived can never truly be sustainable because it’s non-renewable. But I think it’s important to always look at the flip side… Natural aromas can be sustainable, but sometimes they’re not. For example, if they’re taken from marginal habitats (e.g. some frankincense varieties), if they have glacial regrowth periods (e.g. sandalwood), if the plants are endangered (e.g. rosewood, some cedarwoods). Arguably, in these cases, synthetic notes, which we make pretty easily in a lab without a huge environmental effect, may be the more sustainable option. Coming to allergenicity, I think a lot of people will be surprised to hear that certain natural fragrances are actually among the most allergenic fragrances used in cosmetics today. Just because it’s potentially allergenic though, doesn’t necessarily mean that it’s going to cause you an allergy, just like synthetic notes. Ultimately, all fragrances are allergenic and all fragrances need to be used with respect and properly diluted to mitigate these risks.


There are thousands of different synthetic notes to choose from, as well as many pre-made synthetic accords to work with, for example, chypre, musks, fruit (e.g. pineapple), aquatic (e.g. beach or water ‘smells), green (e.g. grass) and gourmand (e.g. toffee) accords. In our last post about fragrances, we went through the various fragrance families. For more on this topic, click here to give it a read! Today there’s also a lot of research and development being put into biotech (which many may classify as synthetic); often fermentation reactions to create different aromas, chemically identical to their natural counterparts (i.e. nature identical). For example rose otto, which because of the fact it requires about 10000 lbs of plant material to often extract a single pound of essential oil, biotech might be the path forward for it, as well as many other natural aromas that are more intensive to produce. These natural fragrances, without biotech, will have a hard time surviving into the future with all of the pressures of our changing climate. If you’ve listened to my podcast, you’ll know that I’m a big fan of this research and it’s potential for sustainable ingredients, but that’s about all the detail I’ll go into about biotech fragrances. Today there’s really not that many biotech fragrances available to especially the smaller brands, but you can be sure that over the next 20 years, that’s going to probably change.

 

In contrast to synthetic perfumes, natural perfumery relies on natural aromas, which comes with their own unique challenges. Plants from different regions of the world will have their own unique chemical profile in their essential oils. For example, with lavender, in different regions of the world, some will contain a higher percentage of linalool, some a higher percentage of linalyl acetate, some may be more camphorous, and so on. This is because essential oils are really there to protect the plant and help it thrive in its environment. As things like climate, elevation, soil quality or pests vary, so will the constituents in the essential oils, and as the constituents change, so does the smell. To make things even more challenging, the constituents of the same plant will vary throughout the season as well. When you make a perfume for the market, you usually want it to consistently smell the same (which is why synthetic aromas are usually easier to work with), but because of all of these variations, that can be pretty tough in natural perfumery. Many industry perfumers will, as a result, only source their essential oils from specific locations and plants at a specific time of the year. Other things that can be a bit challenging include how complex essential oils compared to synthetic notes - usually, less is more in natural perfumery to avoid muddling the end smell. Finally, natural aromas typically have less longevity throughout the day then synthetic fragrances, although this can be combated by including more heavy base notes to help ‘ground’ the perfume. At the end of the day though, these challenges are part of the reason why I love natural perfumery.

Here's an example of small variations with ylang-ylang in chemical compositions between different samples of the same plant.

 

The rest of this blog post will focus on forms of natural aromas out there!


Essential Oils


These are the building blocks for natural perfumes. Essential oils are the aromatic (smelly) volatile (they’ll quickly evaporate and they’re super small molecules generally) chemicals of aromatic plants; they are secondary metabolites that, as I mentioned above, help plants thrive in their environments. Ultimately, all of the natural aromas include essential oils, but when we think of essential oils, we usually mean the ones that have been extracted via steam distillation or cold pressing. Note, both extraction methods can damage the constituents of an essential oil, resulting in not a complete profile of the smell. For example, because of the heat of steam distillation, some of the more volatile components of essential oils will often not survive the process. The overall temperature in general during steam distillation will have a big impact on the overall quality of the end essential oil. For more on essential oils, click here, and for more specifically on their chemistries, click here.

Here's a great infographic on how steam distillation works by Dr.EricZ.com


Absolutes


This process is typically used for plants that are more difficult to extract the essential oils efficiently, for example, jasmine or rose otto. Compared to the essential oils, because this process is more efficient at extracting the essential oils, absolutes will typically have a more complete profile of an aroma, chemically speaking. Absolutes are usually made via solvent extraction, which can vary from synthetic to natural solvents, e.g. petroleum ether, methanol, ethanol or hexane. The solvent pulls out the chlorophyll and other plant materials, resulting in a colored viscous solvent known as a concrete, which contains the waxes/fats as well as aromas. The concrete is then mixed with alcohol to extract the aromatic materials, this final product will be the absolute. The processed concrete can be used to form floral waxes, which are useful in solid perfumes. Absolutes are more commonly used in perfumery rather than aromatherapy, compared to the essential oils above.

Here's a great infographic by New Directions Aromatics to take you through absolute production.

CO2 Extracts


These essential oils have been extracted via carbon dioxide. Carbon dioxide can be pressurized to become liquid, which can act as a solvent and produce aromatic oils similar to absolutes. CO2 is then brought back to the gaseous state to leave you with a CO2 Extract. The big advantage of CO2 extracts over other methods is that none of the constituents (or very little) are damaged during the process and you don’t really have to worry about solvent residue, such as in the case of absolutes. This method is a wee bit newer compared to the other extraction types but because of how efficient it is, I think over the next few decades it will become a lot more popular than it currently is. CO2 extracts can either be partial (i.e. CO2 Selects), which extracts only certain constituents and generally happens at a lower pressure, or complete (i.e. CO2 Totals), which happens at a higher CO2 pressure and captures pretty well all of the constituents.

Here's another great infographic by New Directions Aromatics to take you through CO2 extraction.

 

And that’s a wrap! To avoid writing a book here, I think this is a good place to stop. Hopefully, after this post, you have a better understanding of the types of fragrance material out there and the differences between them. Questions, queries, conundrums or concerns? Leave them below in the comments section or on any of our social media feeds!