Coffee farmers, dawn breaks and it's time to get up. Still sleepy, you make your first cup of coffee , waking up as you take a deep breath and enjoy the wonderful aroma that fills your home. There's no smell like it: sweet, roasted, complex, enough to put a smile on your face. But what is that aroma , why does coffee smell so good, and ultimately how does this affect its flavor?
Whether you're a coffee connoisseur or don't care much about where you get your coffee, no one can deny that the aroma of a cup of coffee is electrifying. Starting your day with energy may be the goal of morning coffee, but caffeine itself is odorless and tasteless, and it's a variety of other compounds that contribute to its aroma.
In its most basic form, aroma is responsible for many of the flavor attributes not directly perceived by the tongue (such as sweet, salty, bitter, sour, and umami). There are over 800 known aromatics in coffee, and new ones are regularly discovered thanks to advances in tasting equipment.
Because aroma is the release of coffee compounds through the air, freshly brewed coffee will have a much stronger aroma than aged coffee. It changes and becomes detectable, meaning the aroma becomes stronger. Without its scent, coffee would only taste sour or bitter due to the organic acids. Try it with your next cup of coffee: hold your nose as you take the first sip.
The rich, satisfying sensation of coffee is almost entirely due to the volatile compounds produced when we roast coffee beans. The compounds formed during the roasting process are very similar to any other compounds formed during the cooking process.
What we smell in coffee
Approximately 800 different compounds are produced during the coffee roasting process. These thermal degradation reactions break down sugars and proteins to form the volatile compounds we smell.
Most of these reactions take place within the thick cell walls of coffee beans, which act as tiny pressure chambers. However, not all of these 800 compounds cause the same response in the olfactory membrane of the nose.
Green (unroasted) coffee has a very grassy flavor when brewed. You still get the organic acids and caffeine in the brew, but it lacks the full flavor because there are fewer volatile compounds due to the lack of roasting.
The profile of roasted coffee includes only 20 major compounds, but it's the influence of some of the minor compounds that determine the overall flavor we experience. When chemists analyze the volatile compounds in coffee, a wide range of different odor qualities are experienced.
Some nitrogen-containing compounds, such as pyridine, can smell quite unpleasant, while others can smell quite fruity.
Other compounds have descriptors like putrid or rancid. One compound, 5-methyl furfural, is described as similar to coffee. But it's the rich mixture of hundreds of different volatile compounds that, when we smell it, we can only describe it as "coffee."
A whole series of studies has been dedicated to discerning which of these extracted compounds contribute to the aroma of a cup of coffee . While over a thousand different chemical entities have been identified in coffee beans, and a significant number of them will be extracted during brewing, it is a small set of chemicals that impact coffee aroma . Studies often consider two main factors when discerning a compoundβs aroma impact: the compoundβs concentration and the compoundβs odor threshold, or the minimum concentration at which we can detect its scent. The ratio of a compoundβs concentration to its odor threshold gives compounds their βodor activity valueβ (OAV), which measures their importance to the overall aroma.
A 2008 study found that the smell of coffee beans affected the activity of genes and proteins in the brains of rats, some of which were linked to stress relief. While rat and human brains differ, this could suggest that the importance of morning coffee isn't just a consequence of its caffeine content, but directly related to its aroma.
Now we know where that exciting, awakening, and even welcoming aroma comes from at home. With this, it's clear to us that the aroma of coffee is what gives us the complexity of flavor and allows us to recognize a special coffee from a distance. So let's do coffee justice and remember that quality and freshness are best.