1.- Origins of fermentation.
 
Fermentation is older than any ancient civilization that we know of today. Several archaeological excavations have found jars with the remains of wine that are approximately 8,000 years old.
 
After much trial, error and careful observation, almost all civilizations began producing fermented beverages (and foods as well), but mainly wine and beer. It started with the fermentation of water with honey in Asia, then the Egyptians, Babylonians and Romans used grapes to produce wine, the Chinese used rice instead to produce wine and other civilizations produced beer with barley. Chicha was produced in South America, through the fermentation of corn.
 
In those days people started to leave fruits and grains in closed containers, because they knew that after a long time, that would turn into wine or beer. But no one really understood how the recipe worked. The process was called fermentation, which comes from the Latin "Fervere" which means "To Boil". The name was created because after a time of leaving the fruit in the vessels, people saw the mixture bubbling, so they thought it was boiling.
 
Producing fermented beverages at the time was complicated, if the mixture didn't stay long enough in the container, the result would not have alcohol at all; but if you left it too long, it was undrinkable. After much observation, people understood that temperature and air exposure were critical to the fermentation process.

​2.- What is fermentation.
 
First of all, we must say that the general definitions of fermentation do not apply directly to coffee. This is because coffee is not a fermented beverage like wine or beer, but coffee production processes USE FERMENTATION AS A TOOL, either to break the mucilage structure and facilitate the execution of a certain processing method (Washed, Giling Basah, etc) and/or directly influence the quality and flavor of the bean (Natural, Honey, Washed, Giling Basah, Experimental, etc). Almost all the different coffee processing methods in the world use fermentation in one way or another, with the sole exception of mechanical washing.
 
So now that we've made this exception regarding to coffee, let's go back to the more general concepts of fermentation. In very simple words, fermentation is a TRANSFORMATION of a complex element into another much simpler one. OK, that's perhaps too simplistic! :)
 
Now more in depth: fermentation is a metabolic process that converts sugars into acids, gases or alcohol.
 
Louis Pasteur, the father of microbiology, who is responsible for all our understanding of fermentation today, pointed out in 1856 that there are two types of fermentation: Alcoholic and Lactic Acid. Alcoholic fermentation occurs through the action of yeast, lactic fermentation occurs through the action of bacteria.

3.- Coffee Fermentation.
 
As we already know, fermentation is a metabolic process of transformation of simple sugars into acids or alcohol. This can be divided into two main groups: alcoholic fermentation (produced by the effect of yeast) and lactic acid (produced by the effect of bacteria). But the variety of microbiota (that is, yeast + bacteria) that are involved in the fermentation process of coffee, is still poorly understood from a scientific point of view.
 
A study that we could find on "Mucilage Fermentation" from 2004 in Nicaragua (SC Jackels. Dept. of Chemistry, Seattle Univ.), Took samples from 7 different lots that were fermented in concrete tanks for periods between 10 to 24 hrs at a temperature of between 21 - 23 ºC; and concluded that: (1) in all samples the glucose level decreased constantly throughout the entire process; (2) that the levels of lactic acid and / or ethanol increased exponentially only in the last 3 hours of the fermentation process; (3) and perhaps the most important discovery, the PH level is a fundamental factor in determining when the fermentation would be complete, without developing unpleasant over fermented flavours (produced by acetic acid and ethanol), and this value on average was PH = 4,6.
 
The coffee microbiota has spread throughout the world along with its plants through human activity (Current Biology 26, 965–971, April 4, 2016). But also, the more "artisan" styles of coffee fermentation have generated several microbiota strains with independent origins. In other words, the bacteria and yeast found in Africa are different from those in South America, and these are different from those in Asia. These could play a much more important role in the development of unique cup profiles for different origins of the world, or what would be known as the "MICROBIOTIC TERROIR".

​4.- Types of Fermentation.
 
With this post we end this series of four articles where we have tried to understand fermentation in depth. First through its history, then understanding what exactly is fermentation, following on how it is used in coffee production; and finally we will see in detail the types of fermentation that are currently used around the world of specialty coffee.
 
We must say that the following types of fermentation, in the industry are called "experimental processes", and refer EXCLUSIVELY TO THE ENVIRONMENT where the coffee is fermented, and not to the metabolic process of fermentation, which by definition is anaerobic, meaning, free of oxygen.
 
AEROBIC FERMENTATION: Implies that the fermentation stage is carried out in an environment high in oxygen. It is the most widely form of fermentation used in coffee; and it occurs during the FW process when we dry-ferment (without water) coffee in a tank, or when we dry natural or honey processed coffee on African beds or concrete patios.
 
ANAEROBIC FERMENTATION: Implies that the fermentation stage is carried out in a low or no oxygen environment. An example, take place during the FW process when we wet ferment (soak) coffee in a tank with water.
 
LACTIC FERMENTATION: Generally is carried out in a steel tank in an anaerobic environment. After pulping, it's assumed that only the especies of bacteria which transform  glucose into lactic acid are alive. There is little scientific support to this, since there are other microorganisms (like yeast) that can also survive in low oxygen environments and could also influence the final result of this type of fermentation.
 
CARBONIC MACERATION: Process borrowed from the French wine industry, and made popular by Sasa Sestic WBC 2015. The process is similar to that described above, but fermentation is done with the whole cherry without pulping. Fermentation here may take days or even weeks since the cherries are left intact.
 
YEAST FERMENTATION: As we have said, yeast and bacteria are microorganisms present in the soil, water, air, tank, pulp, etc. But this process refers exclusively to the adhesion of commercial yeast strains (generally the one used in the wine industry) to the tank, where a wet anaerobic fermentation is being carried out.
 
To wrapped out, we just want to say that all these experiments are great, because this industry has been built and grow on experimentation; but not because a process has a "funky" or "trendy" name it will be better than another which is simply called "washed" or "natural". Let's select our coffees by their cup profile and not by their names.
 
Honorable mention to many people from whom we borrow info (all references on our blog), and especially to Lucia Solis from the "Making Coffee" podcast.
 
THE END

​Suppose we are going to process the lot A, which will be separated according to a series of characteristics that in the industry we call traceability (origin, altitude, process, cultivation, fermentation, etc.); The quality of lot A will be defined by the way in which its cherries are harvested. After the harvest, there will be no possibility of increasing the quality of this lot, we can only maintain it and try very hard not to reduce it.

​Today, we often hear about processes with different types of experimental fermentations, which tend to confuse the expectations of our customers, and we may forget that coffee is the result of the sum of many factors and circumstances, which go beyond one or another specific fermentation.

​In Kilimanjaro Specialty Coffees we find it very positive that producers and importers continue experimenting with processes and fermentations that allow the development of the industry; but we also hope that these flashy names are not used to influence a purchase decision, or as a tool to charge more for a lot that perhaps was not harvested the right way, and it is assumed that just by having a "funky" fermentation the lot will develop a certain flavor, sweetness or quality. This is important, since otherwise we would be replicating the model followed in Indonesia with the Kopi Luwak, where due to the wonders of nature and the well developed nose of the civet, when in freedom, it was able to select the cherries with the greater amount of sugars (selective picking), and the quality of the coffee was given in the first place for this reason and not only by "intraintestinal" fermentation. Then we all know what happened to the sadly famous Kopi Luwak.

​For this reason, it is essential for us to travel every year to origin in harvest time, and observe first hand the standards that will dictate the quality of the lots that we will bring to Barcelona.

Enjoy your coffee and remember that quality is the result of the sum of many factors and not just one of them.

​But how has this happened? How can such an underestimated and undervalued origin by the world of specialty coffee, can become a new quality trend in many countries, and a No. 1 favourite for many coffee enthusiasts around the world in such a short time?

We believe that the answer to these questions is based on three fundamental changes that Sumatran producers understood, adopted and were willing to work very hard to achieve.

1.- Low price of coffee: We all want to live well, we all have bills to pay and we all want to give our children a good education. Sumatran coffee growers are no exception to that, and they understood that the key to improving their quality of life was to concentrate on producing high quality lots in order to obtain better prices. The only way that "C" prices would work in real life, it would be for a large estate, with many hectares of land and with large volumes of production. For small coffee farmers who own less than one hectare of cultivated land, the focus must be on high quality coffee and intercropping.

​2.- Traceability: today in Sumatra, it is not uncommon to find small cooperatives dedicated to producing traditionally cultivated coffees, in a specific area, with a determined variety and produced by a small and identifiable group of people. The lots are fully traceable, to a small village or a small group of coffee growers. This reality responds to a worldwide demand for quality and reliable information. Unlike before, when most of Sumatra's coffee was sold under the name of "Sumatra Mandheling," when there is no place, call Mandheling in Sumatra.

​Processing methods: There are many producers who are experimenting with different processing methods and fermentations in Sumatra. Although, these are new and powerful tools for them, they are improving and gaining experience quickly. We really hope that very soon we will be able to be buying natural, honeys, wine, and more lots with experimental processing methods, but until today we do not believe that the industry has reached that level yet. But there is one processing method that for us is the King, and until today, we haven’t been able to find any better coming from this exotic island and neither from the whole Indonesian Archipelago. This is Giling Basah! If you don’t know what Giling Basah is, please check our Youtube channel, we have a couple of explanatory videos there, both in English and Spanish. We'll leave the link of our channel in the bio.

Enjoy your Sumatran Coffee, and always remember: DO NOT buy cheap coffee!

​1º THE DENSITY OF THE LOT

During the washing process, there are many more opportunities for selection and grading than in the natural process. Although, lately in origins such as Ethiopia and Burundi, where there are cooperatives focusing on quality, they have begun to introduce hand selection and flotation grading, prior to the drying of the cherries on patios or African beds.

This "lack" of selection and grading during the dry process, generates big differences in the density, moisture content, sugar content and cellular structure of the beans of a certain lot.
​
Therefore, to obtain consistent results during your roasting, it will be necessary to adjust your profile, which should be different from the one you use for high altitude washed coffees, and also different from the one you use for Brazilians naturals, since these beans are less dense than those from Ethiopia or Burundi for example.

​2º METABOLIC EVENTS THAT OCCUR IN THE BEAN DURING DP

During the dry process, a series of important metabolic events occurs within the bean that are almost imperceptible to the human eye, but very much to the taste buds!

In the cell wall structure of the bean, there is a significant mutation of organic and inorganic compounds, a migration of low molecular weight sugars (such as sucrose, glucose and fructose), and a relative (but not absolute) increase of polysaccharides and acetic acid.

​3º PRACTICAL ASPECTS TO CONSIDER

- Start your roast with a lower charge temperature. (25% less than  what you use your high-density washed profile is a good starting point)
- Try to stretch the drying stage, so you can "thermally align" the whole batch.
- Reduce the amount of energy input (with air flow and/or gas) when the crack begins, but without extending its development for more than 1.30 min.

We hope this article become useful and let us know in the comments what is your experience roasting natural coffees from Ethiopia or Burundi!

​Only two centuries ago, we began to understand this important process, when in 1854 the French chemist Louis Pasteur determined that fermentation is caused by yeast. In very simple terms, yeast is an unicellular microorganism classified as a fungus, which perform the decomposition of sugars by alcoholic fermentation.

Today, the importance of fermentation and yeast in the production of beverages and food is absolute. Various studies, for example, show that the yeast associated with wine or chocolate fermentation, significantly influences its properties, including its flavour and aroma.

​Fortunately, and despite the fact that the microbiota of coffee fermentation is still mysterious and poorly understood, more studies are being conducted to understand the impact of fermentation and yeast on our cup result.

A very interesting study was conducted in 2016 by Dr. Aimee Dudley and her team. They were trying to determine if the specific yeast of coffee was transported through their plants and human activity, or if particular regions of the world harbor these specific populations of yeast?

​The results were striking, since it was discovered that unlike wine, the more natural styles of coffee fermentation, have generated several yeast strains with independent origins. It was also found that the strains associated to coffee from specific places, are the result of a mixture of yeast strains from different parts of the world.

Considering that the varieties of yeast found in coffee fermentations are genetically more diverse than those of wine, they could play a much more important role in the development of coffee properties in different parts of the world, or what would be known as the "MICROBIAL TERROIR".

After the first selection, the outer skin and the pulp of the coffee cherries will be removed, using a locally built mechanical pulping machines, traditionally called "luwak". Right after pulping, overnight fermentation is needed for breaking the thick structure of the mucilage attached to the parchment. The following morning, the coffee is washed and there will be a 2nd selection, again by density, to remove the remaining floaters.

​Hulling machines in Sumatra are bigger and more powerful than normal hulling machines, because they need to generate more power and friction to strip off the still parchment from the still wet green bean. After the hulling, the green bean will emerge swollen and with a whitish/blueish color.

​For the second time, the green bean naked will go into drying again, until it reaches 12% moisture content. 

The final stage of the process is grading; or what we call the Triple Pick (TP). This stage includes the gravitational grading, size grading and hand sorting.