Coffee Processing Methods | Hartmann Red Wine Processing Principle? Yemen Mocha | Ethiopian Harar | Brazil

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Coffee Processing Methods | Hartmann Red Wine Processing Principle? Yemen Mocha | Ethiopia Harar | Brazil Traditional Natural Sun Drying Process?

The red wine processing method for coffee beans, also known as the red wine-like processing method, is inspired by the winemaking process. Currently, only eight estates in Colombia have successfully brought coffee beans processed using this method to market. According to information from these eight estates, we can broadly categorize the types of red wine processing into: acetic fermentation (Aerobic fermentation), lactic acid fermentation (Anaerobic fermentation), and mixed fermentation (Mix Fermentation = Aerobic + Anaerobic).

Traditional processing methods make it difficult to control the variable fermentation degree of coffee beans. However, the red wine processing method can ensure coffee bean quality by controlling pH values, and even temperature and humidity, while sealed fermentation prevents aromatic substances from volatilizing easily. The red wine processing method for coffee beans, also known as the red wine-like processing method, is inspired by the winemaking process. Currently, only eight estates in Colombia have successfully brought coffee beans processed using this method to market. According to information from these eight estates, we can broadly categorize the types of red wine processing into: acetic fermentation (Aerobic fermentation), lactic acid fermentation (Anaerobic fermentation), and mixed fermentation (Mix Fermentation = Aerobic + Anaerobic).

As for the description of the difference between water-based and water-free methods in red wine processing, although the specific details of the red wine processing method are not fully known, the editor has combined the aforementioned information with personal understanding of the wine fermentation process to roughly summarize the process description of the "red wine processing method."

Traditional processing methods make it difficult to control the variable fermentation degree of coffee beans. However, the red wine processing method can ensure coffee bean quality by controlling pH values, and even temperature and humidity, while sealed fermentation prevents aromatic substances from volatilizing easily. Next, let's discuss the specific fermentation process. First, Colombian farmers carefully pick coffee cherries and meticulously select red coffee fruits to ensure that among the selected coffee cherries for processing, the ratio of unripe cherries is less than 2%, defective beans are less than 3%, and floating beans are less than 5%. The selected coffee cherries are placed by farmers in specific containers. However, in any case, this container should have a device similar to a red wine fermentation plug or a one-way exhaust valve. This way, carbon dioxide can escape through this device to control the air concentration in the container. At this time, the coffee cherries in the container undergo acetic fermentation, and the beans produced from this reaction have relatively bright, clean flavors with a lemon-like acidity. The processor injects carbon dioxide into the container to prevent the formation of volatile acids through oxidation. This process is lactic acid fermentation, which produces malic acid and tartaric acid. Since tartaric acid is relatively stable, beans produced through lactic acid fermentation have a mellower acidity, with cheese, nut, and cream flavors.

Natural Process (Dry Process/Natural Method)

The natural process is the oldest and most primitive processing method for coffee beans. Over a thousand years ago, Arabs used this method to process coffee. It involves placing harvested coffee cherries directly on patios for sun exposure (about 27-30 days), drying the moisture content from 60% to about 12%. This processing method is conceptually simple and not expensive, but it has many variables and risks; for a long time, it was used to process beans of lower quality.

Flavor Profile: Soft acidity with uniform bitterness, thick consistency, rich layers, and more noticeable sweetness. High-quality natural beans will have fruity or wine-like aromas.

Sun Drying: Fresh coffee fruits are placed in sun-drying fields for natural sun drying. After about 2-4 weeks of constant turning, they dry naturally until the moisture content reaches about 12%. This ensures even heating of the coffee cherries. After drying, the coffee bean separates from the outer skin, and then a huller removes the pulp, peel, etc., followed by screening to complete the process.

Coffee beans from Yemen Mocha, Ethiopia Harar, Brazil, and Indonesia Sulawesi are often processed using this method.

Washed Process

The washed process is a technique invented by the Dutch in the 18th century, suitable for rainy regions. Although the process is quite cumbersome, it is currently the most common green bean processing method, accounting for about 70% of total coffee production. Harvested berries are processed through a depulper to separate most of the pulp from the coffee beans, then the parchment beans are guided to a clean water tank and soaked in water for fermentation to completely remove the residual pulp layer. Through water processing, unripe beans and defective beans are selected out due to buoyancy, and the fermentation process is easier to control. Therefore, unlike natural beans which may have off-flavors, washed beans present distinct fruit acidity, slightly stronger complexity, and cleaner cup characteristics (no negative flavors exist, such as astringency or sharpness). However, because they are too "clean," the flavor richness is slightly weaker.

Flavor Profile: Stronger acidity, with a cleaner, crisper, and brighter mouthfeel.

Screening Out Floating Beans: Coffee fruits are rinsed with clean water, and unripe fruits floating on the surface are removed.

Pulp Removal: Fresh fruits are sent to a pulp screener for removal of peel and pulp.

Mucilage Removal: Seeds after pulp removal are transferred to fermentation tanks for about 16-36 hours of natural fermentation to dissolve surface mucilage, then cleaned.

Drying and Hulling: Continue sun drying for 1-3 weeks until moisture content drops to 12%, then use a huller to remove the outer shell.

Washed beans have a blue-green color and attractive appearance. Guatemala, Colombia, Blue Mountain, Kona, Kenya, Java, and Panama coffees are all washed beans.

Semi-Washed Process

The semi-washed process, also called wet-hulling or wet-grinding. Unlike other processing methods, this process does not directly dry coffee beans to a moisture content of 11-12%, but first dries them to about 30-35% moisture content before removing the hard outer shell, exposing the surface of the green beans directly, then continues drying until reaching a moisture content that prevents spoilage and facilitates storage. This secondary drying method gives coffee beans a swamp-like dark green appearance. Coffee beans processed through the semi-washed method have lower acidity and thicker characteristics.

The flavor of semi-washed processed coffee falls between that of natural and washed processes. This processing method is popular in Indonesia, with Mandheling mostly using semi-washed processing. Brazil has also started using the semi-washed method in recent years.

The semi-washed process is somewhat similar to the washed process, first removing the outer skin and some pulp of coffee cherry berries, then drying the berries. After the berries are dried, they are moistened again, then special machines are used to grind off the pulp and extract the seeds.

Honey Process

The name honey process comes from the very sticky mucilage layer of coffee beans before sun exposure, which feels as sticky as honey; when coffee pulp separates from coffee beans, the surrounding mucilage layer becomes sticky after sun exposure, absorbing moisture from the air. The "honey" here refers to the mucilage layer of coffee pulp. After harvesting, the fruits are also peeled with a pulping machine to remove the outer skin, leaving the pulp to be sun-dried, allowing the sweetness of the pulp to enter the beans, without requiring as much time as the natural process.

Flavor Profile: Low acidity, higher sweetness, with fruity aromas. The mouthfeel is cleaner than natural beans, and after drying, there's a fermented wine aftertaste.

Skin Removal: Coffee fruits are washed with clean water, then the skin is removed while leaving the pulp.

Sun Drying: The pulp containing sugar is retained for sun drying together. During this stage, constant turning is necessary to avoid mold growth on the green beans.

Obtaining Green Beans: After drying is complete, the pulp, mucilage, and outer shell are removed all at once.

The honey process is currently a popular processing method, with Central American countries such as Costa Rica and El Salvador being experts in this area.

FrontStreet Coffee Recommended Brewing:

Dripper: Hario V60

Water Temperature: 90 degrees

Grind Size: Fuji Royal grinder setting 3.5

Brewing Method: Water-to-coffee ratio 1:15, 15g coffee grounds. First infusion with 25g water, bloom for 25s. Second infusion to 120g water, then stop pouring. Wait until the water level in the coffee bed drops to halfway, then continue pouring slowly until reaching 225g water. Extraction time around 2:00.

Analysis: Using a three-stage brewing method to clearly define the front, middle, and back-end flavors of the coffee. Because the V60 has many ribs and faster drainage speed, stopping pouring can extend the extraction time.

Important Notice :

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