When you first begin drinking coffee, more often than not the first taste impression to most our palette is bitter. We may occasionally taste acidity, but the floral and fruity flavors that coffee connoisseurs like to describe are confusing.
For people who know very little about coffee, they will think that the flavor notes describing the coffee are added flavor substances in drink. In fact, that is not the case. The magic of coffee is that it has thousands of different flavor profiles! So far, we’ve known more than 800 kinds of distinct tastes in coffee, and there are many more to be discovered.
So where do all the varying flavors of coffee come from?
Coffee is a crop similar the fruit and vegetable we eat everyday. Vegetables and fruits in one area have the same attributes, but there are some differences in taste, shape and variety when the environment is different. Once coffee is planted in the ground, it’s origin is the first factor to affect the flavor.
In a map of the world, we can see that most coffee agriculture is distributed between 25 degrees North and South latitude in Africa, Central America, South America, Asia and some island countries. According to the altitude and the climate and soil of each origin, coffee is susceptible to the influence of the environment in the process of coffee growth, which results in different tasting coffee.
On the other hand, the variety of coffee tree also determines the flavor of coffee. For example, in the coffee family tree pictured below, the three thickest branches are Robusta, Arabica and Liberia. These are the three main varieties of coffee at present.
Arabica and Robusta have the largest market share, but the difference is very obvious. It lies in the chemical composition of the two varieties.
We all know that coffee contains caffeine, which is a substance that exhilarates and energizes people. At the same time, caffeine is one of the sources of bitterness. Meanwhile, another substance in coffee is chlorogenic acid which provides acidity and bitter taste. Robusta contains more caffeine and chlorogenic acid than Arabica.
Moreover, Robusta coffee has less sucrose, which brings sweetness, than Arabica. Robusta usually has full body and more bitterness while Arabica has more complexity and higher-quality flavors.
Processing method of coffee is also an important factor on the flavor. The coffee we drink is actually the seeds of coffee fruits called coffee cherries. The parchment, mucilage, and pulp that the seed is surrounded by provide flavor substances for coffee seed.
The three basic processing methods of coffee are washed, natural and honey process.
Natural, as the most primitive processing method, is drying out fresh coffee cherries directly after harvesting. Flavor substances of the whole coffee fruit, i.e. pulp, mucilage and parchment, can be fully absorbed by the seed as well as fermented with many other microorganisms.
The results show that the natural processing produces more winey, berry-like, tropical fruit flavors with a higher sweetness.
Honey process is to remove the pulp and keep mucilage layer of coffee for fermentation and drying. Coffee mucilage contains sugar and microorganisms which enhanced fermentation. Therefore, honey process highlights the sweetness and nutty flavor of the seed itself.
Washed process differs from the former two in its richness and complexity. It usually has a clean, bright citrus flavor.
This is due to the time before drying, pulp and mucilage of washed beans were removed. After the removal of external flavor-producing substances, only the internal flavor substances are left. So washed coffee represents clean and simple flavor characteristics.
In each processing method, we eventually dry the coffee beans to 10-12% moisture content, within which the coffee embryo can remain active.
Once the embryo dies, the flavor substances in coffee will also be quickly lost. This is known as the old crop which has a distinct woody flavor.
There are two kinds of water-induced embryo death, one is that the water content is too low and the embryo is dry out. In this case, coffee beans accelerate staling.
Another case is that the water content is too high, the embryo is prone to mildew and death in the humid environment, and the subsequent impact is that coffee beans become dead beans, or moldy beans.
Similarly, even well-dried coffee beans need to be stored in an appropriate storage environment.
Since coffee beans have very high adsorption, taints or excessive humidity in the storage environment can greatly affect the green beans. Therefore, when we store green beans, we should control the room temperature at 21℃-22℃ and relative humidity in a stable environment of 60% - 65%.
Good storage conditions also affect the flavor of coffee roasting.
The processing methods mentioned above are to change the flavor of coffee fruit through the external structure of the seed, while the roasting process is to present the flavor through the change of chemical substances inside the coffee seed.
From green to roasted beans, more than 800 flavor compounds in coffee have been noted after roasting.
In the process of roasting, organic acids and proteins in coffee beans, which affect the flavor, are constantly decomposing. The darker the roast, the less the retention of acids. Darker roast are known to have lower acidity and higher bitterer.
At the same time, when roasting Italian espresso coffee, it is very common to blend coffee in order to modulate the flavor of coffee.
At the end, the coffee flavor in our cup is adjusted by the barista through a variety of brewing methods, equipment, and skills.
As a coffee enthusiast, our expectation for coffee flavor is changing after every cup. And different people have different preferences. So, what kind of flavor do you like best in coffee?