More Than A Cup Of Black Water

Maybe you have never thought about where your coffee comes from and what process it went through. 

In fact, the coffee we drink comes from coffee trees and the seeds inside their fruit after intense layers of processing. It comes from the mountains where hundreds of flowers bloom and where nature produces thousands of sweet cherries.

What has the coffee seed been through before it becomes a cup of black water in our hands?

The first stage is picking. In the common processing method, fresh fruit is screened by flotation after harvesting. The fresh fruit is put into the flotation tank where the poor quality and lighter weight fresh fruit are removed by flotation before fermentation or drying. The quality and state of fresh fruit will directly affect the quality of fermentation.

Picking

As a stage of cherry selection, picking determines the direction of the whole processing. For specialty coffee, the ripeness and elevation of fresh fruits are essential.

In the picking stage, all red, or even purple-red coffee cherries are picked by professional workers. Commercial use coffee is mostly picked in the way of strip picking; therefore, the maturity of cherry is not uniform.

There will be immature green cherries, over-ripe rotten cherries and dried-on-tree cherries with defective flavors. This is also one of the reasons for impurities, such as astringent and phenolic tastes when cupping.          

There is a higher demand for all-red cherries at high altitudes because the higher the coffee tree growth altitude is, the longer the coffee growth cycle will last, which is conducive to the accumulation of sugar and nutrients. Sugar is the primary source of flavor. The higher the maturity and the sugar content of fresh coffee fruit, the better the quality and flavor of the coffee.

Fresh fruits begin to ferment after harvesting, so it is necessary to carry out the formulation processing soon after harvesting.

Flotation/Sorting

Flotation is a process of removing impurities: through the fluidity and gravity of water, the immature fruits, floaters, withered beans, sticks and leaves that can cause impurities are removed.

After the fresh fruit is soaked in water, the pulp which carries abundant microorganisms will accelerate the fermentation process.

The coffee farmers must pay more attention to the wet surface of the pulp and turn over frequently to avoid the development of mold. In addition to water flotation, the color sorter can also be used for sorting fresh fruit to improve the quality of the finished product.

Fermentation

French microbiologist Pasteur described fermentation as "life without air", which is an essential phase in the flavor development. During fermentation, microorganisms interact with enzymes. Some microorganisms are produced naturally and they can make contact with enzymes directly.

An example is when fruit juice becomes “sour" after growing old. Another kind of microorganism created by human beings is used to create the condition for contacting enzymes, such as making wine by fermentation. In coffee processing, microorganisms in mucilage react with sugar to degrade, resulting in fermentation.

Many variables are affecting the fermentation process as such the shape and material of fermentation tank, the weight and maturity of coffee, initial and environmental temperature, fermentation mode (dry or wet fermentation), water quality and time.

In the process of fermentation, lactic acid and acetic acid are produced with the degree of sugar decomposition. We use the PH tester to detect the degree of fermentation. When PH is below 4, there is a risk of over fermentation; the smell is similar to pickles, rotten fruits and even nail polish.

The thickness of the coffee pulp is an important factor affecting the fermentation degree. The thicker the pulp of coffee beans, the higher the fermentation temperature, the more intense the fermentation. The coffee fragrance will change from fresh fruits to berry-like. The sweet fragrance will be transformed into tropical fruits and rich red wine which is the ideal state of natural fermentation.

 If we reach the smell of rotten bananas, we must immediately make the adjustment plan to avoid over-fermentation by drying them quickly. Wet environment condition is a paradise for bacterial growth. Ventilation during fermentation and dry environment are very important.

Drying

Next, let's talk about drying.

The drying is the preservation of green bean quality and the development of flavor. While maintaining embryo activity, the water content in coffee beans is reduced to the appropriate storage range of green beans: 10-12%. Too little water content of coffee beans will make embryo dry quickly, flavor loss quickly and woody flavor. On the other hand, too much water content will cause embryo growth environment humid and mildew and dead beans.

Drying is not simply a matter of reducing the moisture content of fresh fruits or husked beans. It takes time for fermentation products to interact with seeds to improve the quality of the coffee. The typical drying period is about 23 days. Drying the processed coffee by laying it out on an outdoor patio allows for higher temperatures and faster drying method.

However, overexposure under sunshine can cause the crack the husk and the potential for the green beans to produce mold when they are directly exposed to the microbial environment. In addition, the organic substances inside the coffee beans will be destroyed by high temperatures, which will reduce the retention of flavor substances.

Proper drying is done with a suitable temperature through convective hot air. This method results in only the surface of the coffee drying while the internal moisture will be transferred through multiple layers of organic substances to reduce the moisture and balance the flavor.

Resting

The main purpose of this stage is to stabilize the quality of coffee beans to achieve batch consistency. Coffee with parchments or husks may be unevenly dried. Therefore, it requires at least 4 weeks of resting time to balance moisture so that the flavor can be fully developed and ready for shipment.

Environmental changes are subtle. Usually, we will design the processing plan first, then implement it.  But in reality, we find that the temperature and humidity of the environment are continually changing.

Even in a cool and ventilated place, there will be some fruit that ferments too quickly resulting mildew. It still needs to be turned over in a small range to slow down the fermentation rate.

The uncontrollable factors brought about by this kind of environment increase the difficulty of processing. Depending on the climate and environmental variables of the coffee region, origin farmers must choose the processing factor best suited for their crop.

After our processing, these coffee beans with parchment will be sent to the dry mill for dry processing and become coffee green beans in the hands of the roaster. After roasting, the small roasted beans we see in the coffee shop become the " black water" in our cups.

So as you can see, it's not an easy journey for coffee to end up in a cup.  Not only is this tiny bean interesting, but it is like a precious treasure waiting for you to discover its delicious potential.

Where do flavors come from?

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.

coffee belt

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.

Natural Processing

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.

Honey Processing

Washed process differs from the former two in its richness and complexity. It usually has a clean, bright citrus flavor.

Washed Processing

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.

Washed Processing

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.

Dead beans

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.

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?