When we talk about the “flavour” of coffee, it’s easy to think we’re referring solely to the way it tastes. However, with more than 40 aromatic compounds in every roasted coffee bean, aroma not only affects perceptions of flavour, it can also tell us a lot about the growing conditions, roast profile, and processing methods of the coffee beans themselves.
Yet while green coffee contains the chemical precursors of aroma, it’s up to the roaster to bring out the aromatic compounds by roasting the beans. Before doing this, it’s important to understand what goes into producing the aroma of coffee and how it can be affected by different factors.
I spoke with 2019 World Cup Taster Champion, founder of Sumo Coffee Roasters, and MTPak Coffee Ambassador, Daniel Horbat, to find out more.
See also: What’s The Best Packaging For Storing Coffee At Home?
What Is Aroma?
When green coffee is roasted, more than 800 volatile compounds are produced within the beans. Of these compounds, approximately 5% contribute to a coffee’s “aroma”, the distinctive, typically pleasant, smell apparent when preparing and drinking a cup of coffee. Aroma has a profound impact on the perception of coffee’s flavour, and can often be used to determine its origin, roast profile, and freshness.
In coffee, each aromatic compound produces a different aroma which contributes to the overall flavour profile of the bean. For example, furans produce caramel-like notes, while phenolic compounds, such as guaiacol, produce smoky and spicy aromas.
Daniel Horbat has been working in the coffee industry for nearly two decades. In 2019, he was crowned World Cup Tasters Champion, before going on to open his own roastery in Dublin, called Sumo Coffee Roasters. He tells me that although fragrance and aroma are often used interchangeably when talking about coffee, the two have different meanings.
“Aroma is detected when we add water to coffee grounds,” he says. “Whereas fragrance refers to the smell of dry coffee. Coffee flavour cannot be achieved in the absence of aroma. When you smell it, you already know what flavour to expect.”
One way of looking at it is when you have a cold and your food tastes bland because your sense of smell is compromised. Your taste buds are still active, but the flavour can’t be detected.
There are two ways of perceiving aroma: orthonasal olfaction and retronasal olfaction. Orthonasal olfaction is when we smell coffee through our nose, whereas retronasal olfaction is when aromatic compounds are detected as they travel through the nasal passage when coffee is consumed or present in the mouth.
As well as its importance to the consumers’ sensory experience, aroma also acts as a guide for specialty coffee roasters in determining whether the development of the beans.
“Underdeveloped beans have a grassy aroma,” Daniel explains. “While beans that are roasted too dark will have a rubbery or ashy aroma. These indicators help me understand whether I need to make adjustments to my roasting parameters.”
What Affects The Aroma Of Coffee?
Typically, green coffee beans have no distinguishable smell. It’s not until the coffee is roasted, triggering a series of chemical processes, that aromatic compounds are formed and coffee takes on its distinctive aromas.
A number of chemical precursors, such as sugars, proteins, carbohydrates, and chlorogenic acids, are responsible for this. However, the concentration of these chemical precursors varies depending on a number of different factors, such as varietals, growing conditions, and processing methods. Daniel explains that innovative processing methods like anaerobic fermentation, in which the vessels used to ferment coffee cherries don’t contain any oxygen, can create exotic, pleasant aromas in the cup.
The Specialty Coffee Association (SCA) places coffee aromas into three broad categories: enzymatic, dry distillation, and sugar browning. Enzymatic aromas refer to those created as by-products of enzyme reactions in coffee beans during growth and processing. Some common descriptors of such aroma are fruity, flowery, and herby.
Dry distillation aromas and sugar browning aromas arise during the roasting process. Dry distillation aromas (usually described as carbony, spicy, and resinous) are produced when plant fibers are burned, whereas sugar browning aromas (commonly described as caramel-like, chocolatey, and nutty) develop as a result of the Maillard reaction.
Yet it’s not just the growing conditions and roasting that affects the aroma of coffee; brew methods can also have an impact because of differences in compound polarity.
Research shows that compounds with greater polarity, such as, 2,3-butanedione, extract at a higher rate compared to less polar ones, like β-damascenone. Due to differences in the extraction rates of the compounds, the perceived aroma in a cup of brewed coffee changes with extraction time.
How Packaging Helps Preserve Aroma
As well as influencing the flavour of coffee, aroma can also have a significant impact on freshness, which is broadly defined as the original, unimpaired qualities of coffee.
During roasting, coffee beans lose mass and become more porous, making it easier for the aromatic compounds to escape. If the roasted coffee is not properly stored, it will quickly lose its aromatic compounds, causing it to become flat, bland, and flavourless. Professor Chahan Yeretzian, the head of the Coffee Excellence Center at the Zurich University of Applied Science, says that if you measure the aroma of a roasted coffee bean, you can sometimes detect a loss of freshness after just a day.
If coffee is not protected from external factors, it can also mask the unique characteristics of the beans. As Daniel explains, this is because coffee readily absorbs odours from its surroundings.
“Roasted coffee beans are like sponges that absorb all types of aromas,” he says. “The materials of coffee bags should be high quality to prevent any external odours from entering and obscuring the aroma profile.”
He also recommends that coffee bags are well sealed and fitted with degassing valves to prevent oxidation. Oxidation occurs when coffee comes into contact with oxygen, causing it to become stale and flat.
When tasting coffee, aroma plays a vital role in perceptions of flavour. Without it, the coffee would taste bland, flat, and unexciting. For specialty coffee roasters, it’s important to understand not only what goes into producing aroma, but also how to preserve it.
At MTPak Coffee, we offer a range of sustainable packaging options to help keep your coffee beans fresh, ensuring the best sensory experience for your customers.