Understanding Coffee Aroma : after the workshop.
One of the best ways to start to understand the complexity in coffee is to start to interpret aroma compounds.
This workshop was divided into three segments.
- A calibration using an assortment of spices, herbs, nuts etc. in sniffer jars.
- A presentation on what Coffee aroma is, how it is formed, and a quick look into all the possibilities available.
- And of course….a cupping with the sole intention of aroma identification.
Below is a brief dissection of the workshop for those who couldn’t creep out of their beds on Sunday.
How is aroma in coffee formed?
There are a host of processes that occur in coffee roasting that create aroma compounds. I will just mention the two that are the most important.
- The Maillard reaction (pronounced ‘My- Yar’).
This is a chemical reaction between reducing sugars and amino acids. This reaction potentiates at 145 to 165 degress celsius, but likely starts earlier. Various sugars and amino acids will produce different molecules. This is one way in which coffees become divergent. But of course, it’s not that simple. The Maillard reaction is also dependent on ph, water, and temperature progression in the roasting process and produces a plethora of aroma compounds.
- Caramelization
This is a reaction exclusively with sugars. Caramelization begins around 150- 180 degrees Celsius. As the sugars start caramelizing, its converted to the furan aroma compound group- producing various sweetness associated aroma compounds. This will of course change and/or become more complex as caramelization ensues. Nutty, chocolatey and caramelly notes are common.
The Aromatic bouquet.
The total aromatic profile of a coffee brew is known as the bouquet and can be divided into three categories.
- Fragrance
Experienced when the coffee has been ground but not brewed. Also known as the dry aroma.
- Wet
When hot water is poured onto coffee, the heat from the water changes some of the organic material present in the bean fiber from a liquid to a gaseous state. This forms the most complex mixture of gases in the bouquet.
- Nose
Any gaseous material previously held in the brew is immediately released upon ingestion. The vapours released, travel up into the olfactory epithelium where the aroma is experienced as taste. It’s like backwards aroma perception, also known as retronasal aroma perception. The nose can be experienced more ‘intimately’ if you were to vigorously slurp the coffee, as is performed in a traditional cupping ( tasting). The character of the nose will depend on the degree of roast.
What you can start doing to explore coffee aroma at home.
By using different filters, you can hold back or allow oils through into your cup. The oils in coffee act as an aroma compound carrier. This is incredibly noticeable, especially when comparing a standard drip- paper filtered brew to an espresso extraction. Of course, not everybody has an espresso machine at home or the office. Just think of what uses metal filters. A French- press is a good example, albeit not using any pressure at all. Paper, on-the-other-hand, produces a cup with less oils, and therefore less aroma. This doesn’t mean paper is bad. Paper filtration has it’s own merits. Mostly in the way that it can highlight acidity by removing the buffer- oil.
One needs to realize that the perception of coffee flavour (just like anything else) is a combination of olfaction(nose) and gustation(mouth). By gustation, I’m refering to everything other than aroma, namely- sweet, salt, sour, bitter and savoury. So if you filter out the oils, you might actually be missing out on your coffees potential. It’s a little more complicated than that. Expect a future post elucidating this topic. For now, just keep the concept in mind.
There is no doubt that Coffee aroma plays a critical part in the overall flavour profile of a coffee. Just remember, it’s not all about the aroma.
In roasting-I sometimes opt to portray the coffees gustatory attributes instead. This will of course depend on the character of the coffee.
Enjoy the brews.