What is the method of washing carbon dioxide impregnation? Treatment methods of raw coffee beans

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Sasa, the 2015 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.

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.

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. At present, it is used in wine making, cocoa bean treatment and coffee treatment. "

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 sugars in the pectin layer. Carbohydrates break down lipids, proteins and acids and convert 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.

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. "

Check the fermentation tank built by the project in Ethiopia. Source:

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. As a result, the cup test score was reduced by five points. The coffee tasted insipid and had no distinct flavor. The effects of the water used for fermentation still need to be studied. "

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 with wine and beer brewing techniques. 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. This is really fascinating! I have never seen anyone know so much about climate and how it affects products.

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 monitors and records pH, alcohol and carbon dioxide concentrations to ensure that the desired brewing results are achieved.

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 more importantly, I want to create a technology that can be replicated on the farm side, just like Tim does with his wine. "

The following is the process flow of Sasa:

First of all, remove the peel and pulp in the stainless steel bucket, use stainless steel because we can handle the cleaner flavor of coffee, in addition, we can move the container according to the space temperature; we can also seal these buckets.

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).

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

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 sour taste of acetic acid-which often occurs during three days of dry fermentation.

Sasa wants to know the data of each step like Tim. "We also measure and record the pH, 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:

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 test score of coffee increased by 2.5 points. "said Sasa.

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.