Where does a coffee flavor come from?

The Sensory Experience you perceive when tasting coffee is an accumulation of many things. In this series, we will explore where a coffee flavor comes from. To start out, we will take a dive into what in a coffee’s life contributes to flavor. Keep your eyes peeled to our blog for upcoming posts! They’ll cover each section of the flavor wheel and how specific flavors are created and evolve.

Granted, coffee is made up of more than a thousand flavor compounds. During roasting, hundreds of physical and chemical reactions occur. All this to say, what we explore here is only the tip of the iceberg as far as coffee flavor chemistry goes.

For a clear picture on how your senses work to define how the flavor experience happens anatomically speaking please see our previous post on Tasting Coffee.

Where a coffee flavor comes from: The Basics

Terroir/Origin

The coffee tree doesn’t really know where it is growing per se. Rather, the bean’s chemistry is effected by the soil’s mineral content, the surrounding plants and trees, the topography, the weather, area specific cultivars and common processing techniques for a specific region. For example, the phosphoric acidity (think Coca-Cola like acidity) of a Kenyan coffee can be traced directly to the amount of phosphorus in the soil. Alternatively, the typical flavor profile of a Kenyan coffee is tied to the most common variety grown there, SL-28. When this variety is grown at other origins, it often brings a similar flavor profile to the cup.

Available Nutrition

One reason a slower maturation of coffee cherries is helpful with flavor and sugar development is because it allows for a slower absorption of nutrients. This is opposed to a quick depletion of available nutrients.

The soil around the coffee tree loses SOM (Soil Organic Matter) at a much faster rate than the soil produces more nutrient rich soil from the breakdown of organic matter. We don’t want the coffee to grow so quickly that it absorbs all the nutrients out of the soil faster than the soil can replace them. Nutrients are vital for overall coffee quality. To combat this some producers grow a diverse variety of plants. Moreover, they ‘feed the soil’ either by compost, other fertilizer, or by adding other organic materials directly to the ground.

Organic materials needed, but mineral composition is important as well. Therefore, this is why coffee grows so well in volcanic soil. Phosphorus, nitrogen, potassium, calcium, zinc and boron are all contributors in developing flavor. Potassium influences total sugar and citric acid in a coffee, while nitrogen is a major influencer in the caffeine build. The result of lack of minerals and/or other nutrients is often ‘flatter coffees.’ These have low acidity and very basic flavor profiles.

Weather/Elevation

Weather and elevation are very closely tied together. Meaning, the weather changes as the elevation changes. More rainfall happens and cooler nights occur as you go up a mountain. In Kona, Hawaii most coffees grow between 240 – 800 masl, which is roughly equivalent of Colombia at 1,200 – 1,800 masl, temperature-wise. Kona can get down to the 5C at night, which is comparable to the temperatures at higher elevations in Colombia. This is important because the bean doesn’t know how high it is growing. Higher elevations often lead to climatic conditions that are ideal for specialty coffee. Large variation in temperature from hot days to cool nights forces a slower maturation of the coffee cherry. Moreover, temperature variation increases flavor and sugar development. The closer to the equator, the higher the elevation must be to achieve comparable temperatures.

In general, the higher the elevation, the cooler the nights are. Therefore, the coffee quality is better overall. Furthermore, steep topography is ideal for a coffee-growing climate. It helps with drainage and increases the sun exposure of each individual tree. A tree loves water, but its roots don’t want to be sitting in it! All of this contributes to the resulting cup.

Variety

Varieties of coffee are as different as varieties of apples.  Not all varieties can grow in the same conditions optimally. Additionally, the flavors can range as much as a granny smith and a red delicious apple does.  For instance, a Geisha will most likely have a lighter body, delicate complexity, and floral elements as opposed to a Pacamara grown under the same exact conditions. The Pacamara will be much juicier and heavier in body with malic acidity. One of the reasons variety is less commonly discussed is that multiple varieties are often grown on a farm or in an area, and they are often blended together. For an extensive overview on varieties, we find WCR’s Variety Catalog helpful.

Processing Method

Post-harvest coffee processing seems to be the hot topic in coffee right now. The way a coffee is processed (the method in which the cherry is removed from the seed can drastically effect the flavor of the resulting coffee. The basic ‘styles of processing’ are Natural, Honey, Washed, and Wet-Hulled. There are more experimental methods like the Anaerobic process. Even within each of these methods there are variations that effect the final cup. For instance, in the washed process, how long the cherry stays on the seed for, how long the coffee is fermented for (if it is), and the temperature at which is was fermented, even the chemistry of the water used can affect the flavor of a coffee. Processing is the primary point when most flavor defects can be created if it is not done right.

Drying/Milling

The main factors are how evenly a coffee dries and the length of time the drying process takes. Coffee can take anywhere from a few days to a month and a half depending on the processing style, the weather, and access to resources like mechanical dryers, solar dryers, or raised beds. The drying phase is also a point at which coffee can develop off-putting flavors or defects if it is not handled correctly. Proper drying allows for sugars to be preserved as well as ensuring that the green coffee will stay full of flavor for a prolonged period of time, as opposed to a quick-to-stale coffee.

Roasting

The Roasting process drastically changes a coffee’s flavor attributes. Coffee goes from this hay-smelling green bean to a brown bean with a wide variety of aromatic compounds and flavors. Just like the rest of the factors influencing flavor, roasting is extremely complex in that hundreds of chemical reactions are happening during the process, and it can be similar to a ‘choose your own adventure book’ in that each reaction can lead to a slightly different set of subsequent reactions.

On a broad scale, the main focus of what we talk about is the maillard reaction, which occurs when reducing sugars react with amino acids, repeatedly. These reactions produce melanoidins, which are responsible for coffee’s color, as well as some of the bitter compounds found in coffee, but these reactions can also lead to fruity, floral and sweet aromas. The ‘path’ a coffee takes and the resulting flavor profile is greatly dependent on what is available in the coffee, as well as the application of heat. During roasting, citric and malic acid are quickly dissipating, ascetic acid is being produced, and lipids are forming. All of which which effect the perceived acidity, body, and crema in your final cup.

Bean Age: Green & Roasted

Coffee, just like almost any product, oxidizes (like a banana) and loses organic material and changes in flavor. This is true for both green coffee and roasted coffee, although oxidation and LOM (loss of organic material) happen much slower in green coffee than roasted, mainly due to it’s overall density. Generally speaking, the denser the bean roasted or green the slower it will oxidize and lose available flavor. In green coffee, this leads to ‘papery or woody flavors’ regardless of how the coffee is roasted afterwards. Coffees with high water activity are most likely to age quicker than those with lower water activity. Roasted coffee will lose much of it’s vibrancy and begin to taste ‘flat’ and ‘stale.’ The primary factor you want to avoid when storing coffee is oxygen, followed by moisture and then varying or high temperatures.

Brewing

Depending on your brew recipe a coffee’s flavor will be greatly varied. Depending on your method or recipe for brewing, you can create a sour and thin bodied coffee or an intense and bitter beverage. You can highlight different aspects available in coffee by altering different brew parameters. This all has to do with the amount you extract from the bean and then the strength and intensity you achieve overall in the resulting cup. Which solubles and how much of each of these solubles you extract, can vary greatly based on your temperature, contact time, grind particle size, water composition and more. For instance, harder water will give you heavier more intense brews. A higher brew temperature will not only increase extraction, it will also extract citric acid more easily than malic acid. You can find more information on extraction theory here.

So, there it is, the ‘basics’ of flavor in coffee. Stay tuned to the RNY Blog for a more in depth look into each section of the flavor wheel.