What are the categories of fermentation methods for raw coffee beans? How do different degrees of fermentation affect coffee

Professional coffee knowledge exchange more coffee bean information please follow the coffee workshop (Wechat official account cafe_style)

What are the categories of fermentation methods for raw coffee beans? How does different fermentation degree affect the flavor of coffee beans?

Sasa, the world barista champion, uses an innovative fermentation process called washing carbon dioxide impregnation, and two years later he has his own estate and is more involved in fermentation technology.

In fact, at the Budapest World Competition in June 17, Sasa gave a speech on controlling the flavor, quality and price stability of fermentation treatment, and he agreed to provide us with some of the information of the speech.

Coffee with endocarp after fermentation

After the coffee is harvested manually or by a harvester, how to get the kernel out of the coffee fruit?

In fact, it is not easy, because coffee fruit in addition to the core (that is, we now eat coffee beans Coffee beans), but also contains the peel (Skin), pulp (Pulp), fruit (Parchment), silver film (Sliver Skin) a total of five parts, and take out the coffee beans this way is called processing, treatment-it has drying (also known as non-water washing and natural or sun-drying), water washing, semi-washing three ways.

1. Dry fermentation (Dry process/Natural method):

Arabs knew how to use this method to deal with coffee beans more than a thousand years ago, but there must be more than 20 days of sunny days before coffee beans will not go bad, and the drying method is to actually expose the freshly harvested coffee fruit to the sun until it makes a clap, and then use a sheller to remove the skin, pulp and silver skin that has already been dried. Dry coffee beans are better than water-washed beans under favorable conditions, because the seeds fully absorb the aroma and sweetness of the flesh, and then are exposed to the sun, so they have soft acidity and uniform bitterness, and the flavor is better than that of water-washed beans. Consistency is also better; but beans are often defective and not very beautiful In addition, this method will also mix immature and defective beans and impurities and will be affected by the weather, so it must be carefully picked before shipment. Almost all countries such as Brazil, Yemen and Ethiopia get coffee beans by drying.

two。 Washing fermentation (Wet process/Washed method):

This is the technology started by the Dutch in the 18th century, suitable for rainy areas. In other words, the immature fruit and impurities floating on the surface of the raw coffee fruit are removed by running water, then the pulp and skin are removed by the pulp removal machine, and then fermented in a fermentation tank for one or two days, the pectin on the surface of the coffee fruit is dissolved, and then washed with water. after drying for a few days, the endocarp is removed by a sheller, which is quite cumbersome. However, the color of the obtained coffee beans is more glossy and less impurities. At present, Mexico, Colombia... Coffee beans are handled in this way in several countries. Washed coffee beans account for about 70% of all coffee. But the process of fermentation is very important, if handled properly, it can give off the advantages of coffee beans (that is, fragrance); otherwise, it will emit sour taste and fermentation smell.

This is also an important factor affecting quality and price. Generally speaking, the coffee washed by water has a bright and clean taste and a strong sour taste, but the consistency of the brewed coffee is slightly lower.

3. Semi-washing fermentation (Semi washed method):

Its method is somewhat similar to the washing type, except that the coffee fruit is not put into the fermentation tank, but the peel of the coffee is removed directly with a peeling machine, and then spread on the ground to dry it, then soak it, and then use a special machine to grind off the dried fruit and remove the raw coffee beans.

At present, most of the Mantenin produced in Indonesia are semi-washed. Semi-washed beans, the flavor is between drying and washing. And then according to the quality, size... With equal classification, it can be put into sacks and special containers for export and crossing the sea.

4. Anaerobic fermentation treatment:

100% ripe fruit is collected manually for 'anaerobic fermentation', and the average fermentation time is about 24 hours! At this time, there are four major elements of the treatment.

1, shade system shade can effectively block the sun, so that the pulp can produce more sugar, making the final coffee has more sweetness and wonderful acid value.

2. Stainless steel container (this is the most important)

Coffee beans are fermented in stainless steel containers as soon as they are picked, instead of using traditional cement or other containers, because these traditional containers absorb the flavor of coffee beans and do not retain more coffee flavor in the pulp of coffee. Stainless steel containers can make the flavor of coffee cleaner.

3. The coffee beans put carbon dioxide in the stainless steel container will be sealed and pressurized with carbon dioxide in the barrel so that there is no air in the container, which ensures that the flavor and aroma of all coffee are retained in the coffee. The original flavor of coffee is more obvious.

4. Controllable temperature these coffee beans are all in a temperature-controlled environment, so that the coffee beans have the same flavor, while the traditional treatment method can keep the same flavor of the beans each time.

[pressure honey treatment] is now very ramming anaerobic treatment or so-called anaerobic fermentation!

That is the pressure honey treatment, which is the same as making red wine, put the removed coffee pulp and pectin coffee beans into a stainless steel bucket to ferment, the pressure in the barrel fermentation rate becomes very slow, so that the coffee has more sweetness and wonderful acid value! This is the ultimate goal!

But: do not think that this is a panacea, coffee is good or bad or return to the essence, good raw beans + good handling, is good coffee beans, do not listen to some masters nonsense, Taiwan coffee through this technology can be unparalleled, score 94, master, this system is still developed by the Taiwanese, carried forward in Costa Rica, where who developed it, left to the master guess, can not be too many masters!

Why are we talking about fermentation?

Sasa mentioned that we know little about fermentation, but it is very important.

He said at the meeting: "I flew to countries around the world to taste coffee and tested the coffee processing process with more than 50 farmers. I also experimented on my own farm and found that there were too many unstable factors in the traditional treatment methods in the past. The most unstable of which is the effect of fermentation.

He mentioned that in fact, there are some examples of how fermentation can improve or reduce the quality of coffee or even reach an eight-point difference. When most boutique coffee scores are defined at 80-92 out of 100, eight is a startling difference.

Iced coffee in Sasa experiment, cup score was 87.5 points, source: Sasa Sestic

What is fermentation?

Simply put, fermentation is the process by which sugars and starches break down into acids or alcohol. Let's delve deeper. Sasa says yeast and bacteria are important for fermentation.

Yeast fermentation, called Saccharomyces cerevisiae, is a natural wild yeast that is also found in grapes, cocoa beans and other fruits. It is currently used in wine making, cocoa bean processing and coffee processing. "

And the strain is lactic acid bacteria.

During the natural fermentation of coffee, different biodegradation procedures take place, and enzymes produced by yeasts and bacteria begin to decompose the sugar in the pectin layer. Sugar breaks down lipids, proteins and acids and converts them into alkyd, which changes the smell, color, pH and composition of the pectin layer of coffee beans.

Sasa also said that there are many different fermentation methods in the world, but they are mainly divided into dry fermentation and wet fermentation.

Dry fermentation and its flavor

"after we remove the pulp, we put the coffee with endocarp in the fermentation tank, and the fermentation promotes the sweetness, chocolate and fruit flavor of the coffee." but one of the challenges of fermentation is temperature control. Since temperature can affect the degree of fermentation, it will also negatively affect the stability and flavor of the process.

Effect of temperature on dry fermentation, source: Sasa Sestic

The diagram on the left side of the dotted line above shows that we ferment the coffee at an average temperature of 16 degrees for 24 hours. The coffee tastes great and the flavor is well balanced.

The right side of the image above represents fermentation at a temperature of 26 degrees for 24 hours, with marked pink blocks, which can occur when the fermentation is too long, and alcoholic acids dominate the fermentation, resulting in excessive acetic acid, dryness and metallic taste.

Wet fermentation and its flavor

You may have heard someone describe wet fermentation as double washing, double fermentation, Kenyan washing, etc., which is common in East African countries and is famous for its clean and clear flavor, but Sasa describes this treatment as adding flavor to the cup.

"when we remove the pulp and put the coffee with endocarp into the water, the water will help prolong the fermentation time, resulting in a softer mellow thickness, rich acidity and more elegant flavor characteristics of the coffee."

Fermentation tank built by the inspection program in Ethiopia, source: Project Origin

Of course, this does not mean that the treatment is not challenging. Sasa mentioned that temperature and water quality can also affect the results.

Sasa: "A few years ago, I did an experiment with Raul Riviera, the owner of Santa Rosa in El Salvador. We used Rain Water instead of spring water to ferment. Rain Water would absorb a lot of fruit flavor and sugar from the coffee fruit, resulting in a five-point drop in the cup test score. The coffee tasted insipid and had no distinct flavor. The effects of the water used for fermentation still need to be studied. "

The left side of the picture above shows the coffee fruit soaked in spring water for 30 hours with a ph of 7.5 / TDS 180.

The right side of the image above shows Rain Water's coffee fruit soaked for 30 hours, with a ph of 6.5 / TDS 30.

More data makes better coffee

Sasa is one of the leaders in coffee treatment experiments, from his novel ice treatment (which will be a trade secret until his book is published) to the famous washing carbon dioxide impregnation.

Due to the lack of related research in the coffee industry, Sasa began its research on wine and beer brewing technology. Sasa: "Tim Kirk, the owner of Clonakilla winery, helps me a lot and gives me a lot of inspiration. His winery is in my hometown of Canberra."

"when I first visited Tim, I was impressed by his equipment. He knew very well where Rain Water would land in the vineyard, and he knew very well the temperature of the wind and how it would affect the flavor of the wine. It's really fascinating. I have never seen anyone know so much about climate and how it affects products.

Tim Krk of Clonakilla winery explains the cause of wine fermentation, source: Sasa Sestic

But Tim is not apt to describe the weather like the back of his hand, because he can even control it.

Tim can control the temperature and humidity of the environment during fermentation. He says that as long as he controls different temperature and time, he can make the wine reach different flavor levels.

He uses a double-layer insulated stainless steel container to increase the clarity of the fermentation. He will monitor and record pH, alcohol and carbon dioxide concentrations to ensure that he achieves the desired brewing results.

This data-driven approach has led Sasa to change the way he handles coffee.

Fermentation experiment

"imagine a cup of water-washed and tanned coffee with great flavor and distinctive characteristics. I want to create a treatment technology that can give full play to the aroma and flavor of coffee and have a good balance between sour and sweet taste. And then more importantly, I want to create so that this technology can be replicated on the farm side, just like Tim does with his wine. "

The following is the process flow of Sasa:

Step 1

First, remove the skin and pulp from the stainless steel bucket. "stainless steel is used because we can process coffee with a cleaner flavor, and we can move the container according to the temperature of the space; we can also seal these buckets."

Step 2

Next, move the bucket indoors, where the temperature is easier to control, but Sasa is still collecting data on how this affects coffee processing. However, he has observed some valuable conclusions: "if you want to get rich acid, you should ferment at a lower temperature (4-8 °C)." To get more sweetness, use higher temperature fermentation (18-20 °C).

Coffee fruit in stainless steel buckets before fermentation process, source: Ka'u Specialty Coffee

Step 3

Next, seal the bucket. In my experience, this stage will develop more aromas and add flowers to the coffee.

Step 4

The last and most important step is to inject carbon dioxide. The reason for choosing to inject carbon dioxide is that as long as there is no oxygen, the decomposition of sugar in the pectin layer will be reduced, and the range of pH change will be greatly reduced, which means that we can reduce the production of alcohol acidity.

Carbon dioxide can extend the fermentation time to three days at 22 degrees Celsius, even at low temperatures for a long time, without developing a sense of dryness and the irritating acidity of acetic acid-which often occurs during three days of dry fermentation.

Sasa wants to grasp the data of each step like Tim. "We also measure and record the pH value, carbon dioxide concentration and temperature of the fermentation process, and then we can replicate these fermentation conditions each time."

Carbon dioxide impregnation: carbon dioxide is injected and oxygen is discharged. Source: Sasa Sestic

Continuous improvement method

Sasa is not satisfied with his title: he urges himself to find more ways to improve the flavor of coffee through fermentation. "Last year, I had coffee from Jamison, Morgon Manor in Panama, and it was delicious. But I wanted more sweetness, deeper flavor, and more floral flavor, so after a few cups of yellow soup, we decided to do carbon dioxide impregnation. "

But this is different from the carbon dioxide impregnation method that has been operated in the past. "We decided to ferment coffee at a higher temperature of 20 °C to promote the sweetness of coffee, and to extend the time of carbon dioxide impregnation fermentation to 65 hours to promote the development of more flavor richness." As a result, we get more sweetness, better texture and clearer flavor characteristics. "in the end, the cup score of coffee increased by 2.5 points." Sasa said.

Fermentation monitoring curve, from Sasa Sestic2017's speech in Hungary.

Through this treatment, he brings the desired flavor, and they provide more opportunities for consumers, baristas, coffee contestants to get good coffee, and producers can get a stable good selling price.

"from my point of view, I believe there is no perfect variety of coffee, and there is no perfect way to handle it. However, if we can understand the potential flavor characteristics of different coffee varieties, as well as their advantages and disadvantages, and deal with them through carbon dioxide impregnation or other controlled fermentation methods, we can enhance the advantages and disadvantages of these coffees. When we get good processing data in the fermentation process, we can replicate this beautiful flavor.