Coffee Processing Methods: What Types of Natural Processing Exist? What's the Difference Between Natural and Semi-Natural Processing?

According to FrontStreet Coffee, good processing methods can bring out the rich flavors of coffee. Just as excellent wine requires proper brewing to produce exceptional flavors, processing methods are similarly crucial for green coffee beans. Different processing methods result in distinct flavor characteristics.

Dry Process/Natural Method

The dry process, also known as the natural method, is the oldest and most traditional coffee processing technique. Over a thousand years ago, Arabs used this method to process coffee. The harvested coffee cherries are placed directly on patios to dry under sunlight (approximately 27-30 days), reducing moisture content from 60% to about 12%. This processing method is conceptually simple and cost-effective, but involves many variables and risks. For a long time, it was primarily used for processing lower-quality beans.

Flavor Profile

Natural processed coffees exhibit soft acidity with uniform bitterness, rich body with complex layers, and more pronounced sweetness. High-quality natural processed beans carry fruity or wine-like notes. FrontStreet Coffee recommends their Natural Red Cherry, Flower Champion, and Queen Estate varieties, which showcase the smooth mouthfeel of traditional natural processing. These can be purchased at FrontStreet Coffee's Taobao store or Tmall flagship store.

Natural Drying Process

Fresh coffee fruits are placed on drying patios for sun drying. After approximately 2-4 weeks of constant turning, they naturally dry to about 12% moisture content. This ensures even heating of the coffee cherries. After drying, the coffee bean separates from its outer skin, and then hulling machines remove the pulp, skin, and other layers before sorting completes the process.

This method is commonly used for Yemen Mocha, Ethiopia Harar, Brazilian, and Indonesian Sulawesi coffee beans.

Wet Process/Washed Method

The wet process was invented by the Dutch in the 18th century and is suitable for rainy regions. Although the process is quite complex, it remains the most common green coffee processing method today, accounting for about 70% of total coffee production. Harvested berries are processed through depulpers to separate most of the fruit flesh from the coffee beans. The parchment beans are then guided to a clean water tank and soaked for fermentation to completely remove residual fruit pulp layers. Through water processing, underripe and defective beans are selected out due to buoyancy differences. The fermentation process is also more controllable, resulting in flavors without the impurities found in natural processed beans. Instead, washed coffees present distinct fruit acidity, slightly more complexity, and cleaner cup profiles (without any negative flavors like astringency or sharpness). However, this very "clean" characteristic also results in slightly less body.

Flavor Profile

Washed processed coffees display stronger acidity with a clean, refreshing, and bright mouthfeel. FrontStreet Coffee recommends their Flower Butterfly, Guodingding, and Emerald Geisha varieties.

Washed Process Steps

Removing Floating Beans: Coffee fruits are rinsed with clean water, and immature fruits floating on the surface are removed.

Depulping: Fresh fruits are sent through depulping machines to remove the skin and fruit flesh.

Removing Mucilage: Seeds after depulping are transferred to fermentation tanks, where they naturally ferment for approximately 16-36 hours to dissolve surface mucilage before washing.

Drying and Hulling: Continue sun drying for 1-2 weeks until moisture content reaches 12%, then remove parchment using hulling machines.

Washed processed beans display a bluish-green color with attractive appearance. Guatemala, Colombia, Blue Mountain, Kona, Kenya, Java, and Panama coffees are all washed processed varieties.

Semi-Washed Method

The semi-washed method, also known as the wet-hulling or wet-hulling method, differs from other processing methods in that coffee beans are not dried directly to 11-12% moisture content. Instead, they are first dried to about 30-35% moisture, then the hard outer shell is removed to expose the green bean surface directly. Afterwards, drying continues until reaching a moisture level that prevents spoilage and facilitates storage. This secondary drying method gives coffee beans a swamp-like deep green appearance. Semi-washed processed coffee beans exhibit lower acidity and fuller body characteristics. FrontStreet Coffee recommends their Golden Mandheling coffee beans.

The flavor of semi-washed processed coffee falls between natural and washed methods. This processing method is prevalent in Indonesia, with Mandheling predominantly using semi-washing. Brazil has also begun using semi-washed methods in recent years. The semi-washed method shares similarities with the washed method: first removing the outer skin and part of the fruit flesh from coffee cherry berries, then drying the berries. After the berries dry, they are moistened again, then special machines grind away the fruit flesh to extract the seeds.

Honey Process/Miel Process

The honey process gets its name from the very sticky mucilage layer of coffee beans before drying - the sticky feeling resembles honey. When coffee fruit flesh separates from the coffee bean, the surrounding mucilage layer becomes sticky during sun drying by absorbing moisture from the air. The "honey" here refers to the mucilage layer of the coffee fruit flesh. After harvesting, fruits are de-skinned using depulping machines, leaving the fruit flesh for sun drying, allowing the sweetness of the fruit flesh to penetrate the beans without requiring as much time as the natural method.

Flavor Profile

Honey processed coffees feature low acidity, higher sweetness, and carry fruity aromas. The mouthfeel is cleaner than natural processed beans, with fermented wine-like aftertaste after drying. FrontStreet Coffee recommends their Strawberry Sugar coffee beans.

Honey Process Steps

Removing Fruit Skin: Coffee fruits are cleaned with clean water, then the skin is removed while preserving the fruit flesh.

Sun Drying: The sugar-containing fruit flesh is preserved during sun drying. During this stage, constant turning is necessary to prevent mold growth on the green beans.

Obtaining Green Beans: After drying completion, the fruit flesh, mucilage, and outer shell are removed all at once.

The honey process is currently a popular processing method, with Central American countries like Costa Rica and El Salvador being particularly skilled in this technique.

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