Smell is one of the most primitive of senses; even plants, insects and single celled organisms have it. It allows us to detect chemicals in our surroundings, helping us to avoid nasty things (like stinky dog poo) while indulging in life’s pleasures (like freshly baked bread).
Perfumes are inspired by the natural scents we have evolved to enjoy. For example, the ‘essential oils’ of fruits and flowers are often added to perfumes. These essential oils contain alcohols and chemicals known as ‘esters’, which give them their aromas. Sensors in the nose called ‘olfactory receptors’ bind to these chemicals, based on their specific molecular shape, which then send messages to the olfactory region in the brain. The olfactory regions then interpret the smell, telling you what it is and whether it is something you enjoy. Importantly, the olfactory regions in the brain are very closely linked to the brain’s emotional regions (the limbic system), meaning that emotions follow immediately after a distinctive aroma.
Extraction of essential oils from fruits and flowers is a laborious and low-yielding process. Scientific advances mean that we can now sidestep this and synthesise these fragrances in a lab. (A recent study has even shown that genetically engineered yeast can be used to produce fragrant chemicals!) As the Human Touch of Chemistry tells us: “a mixture that has geraniol, citronellol, phenylethyl alcohol and linalool (all types of alcohol) in a ratio of 30:25:25:5 smells just like roses”. How romantic.
Just like working from a recipe book, we can make many smell-inducing chemicals (esters) by mixing different types of alcohols and acids in the lab. Each ester has a distinct aroma that perfumers use to give their products a sweet edge:
|Alcohol +||Organic acid =||What does it smell like?|
Info sourced from BBC Bitesize.
By Michael McKenna
Elizabeth Bernays. Chemoreception. Encylopaedia Brittannica [website]. http://www.britannica.com/EBchecked/topic/109023/chemoreception. (Accessed 7 March 2015).
Aviva Rutkin. (March 2015). Would you wear yeast perfume? Microbes used to brew scent. New Scientist [website]. http://www.newscientist.com/article/mg22530113.600-modified-yeast-perfume-what-the-future-smells-like.html#.VQAWASi5Kap. (Accessed 7 March 2015).
The Human Touch of Chemistry. What makes perfumes smell nice? The Human Touch of Chemistry. http://humantouchofchemistry.com/what-makes-perfumes-smell-nice.htm. (Accessed 7 March 2015).
BBC. Smells. BBC Bitesize. http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/carbon_chemistry/smellsrev1.shtml. (Accessed 7 March 2015).