Coffee Processing Methods: What's the Difference in Flavor Characteristics Between Anaerobic Natural and Natural Processing?

In pursuit of greater sweetness in coffee, anaerobic processed coffee beans have become very popular in recent years. For example, FrontStreet Coffee's Colombian Flower Moon Night coffee beans use anaerobic natural processing. When prepared as pour-over coffee, they exhibit rich fruit aromas and fermentation notes, with gentle acidity and noticeable sweetness, making them highly popular among coffee enthusiasts.

What is Natural Processing?

Those who have studied coffee processing methods should know that the coffee beans we taste are actually seeds inside the fruit. After coffee cherries are picked, they need to go through a series of steps to remove the pulp and dry them before we obtain the coffee beans we want. Natural processing is the oldest traditional method and also the most common green bean processing method, still widely used in many countries today.

So-called natural processing involves spreading freshly picked coffee cherries under the sun, allowing sunlight to evaporate the moisture from the fruit surrounding the beans. When the target moisture content is reached, the outer shell can be mechanically crushed to extract the parchment coffee beans. Since natural processing doesn't require sophisticated technology, basically every small farmer household can process it themselves. The entire drying process only requires sunlight on clear days, making production costs lower, and it's most common in high-altitude coffee growing regions.

Regions pursuing refined flavors will first float-select the coffee cherries, removing underripe fruits and gravel debris, then spread them evenly on elevated drying beds. The purpose is to keep them away from the ground to prevent infection by crawling insects, dust, and bacteria. During the natural drying period, dedicated personnel will check the drying degree of the coffee cherries and remove worm-infested, burst, and moldy fruits to prevent these bad cherries from affecting other coffee.

Since the inner beans of natural processed coffee are dried while completely wrapped in fruit pulp, the coffee cherries undergo longer fermentation times, with higher degrees of reaction between microbial strains and fruit pulp. When the fruit begins to ferment, microorganisms produce more volatile compounds, especially esters. These aromatic substances provide more floral and tropical fruit fermentation notes for roasted coffee beans, such as furan compounds, which broaden the flavor profile of natural processed coffee and make it taste sweeter. Examples like FrontStreet Coffee's Yirgacheffe Red Cherry coffee, Flower Queen coffee, and Panama Red Label Geisha coffee all use refined natural processing.

What is Anaerobic Natural Processing?

Simply put, anaerobic natural processing is a post-processing method based on natural processing that utilizes modern technology to ferment coffee cherries in an anaerobic environment for a period of time first. Anaerobic natural processing involves placing freshly picked coffee cherries in sealed barrels for low-temperature fermentation. In an anaerobic environment, the decomposition rate of pectin decreases, while the pH value drops more slowly, extending the coffee's fermentation time and thereby developing more sweetness. The entire anaerobic environment requires strict temperature control, averaging between 10 to 15 degrees Celsius.

After more than three days of anaerobic fermentation, the coffee cherries in the barrel undergo natural drying processing. Finally, the dried coffee cherries have their excess parts removed to extract the coffee beans. FrontStreet Coffee's Colombian Flower Moon Night coffee beans are processed using this anaerobic natural method. This Flower Moon Night coffee bean gains richer mature fruit acidity and fermentation aromas due to anaerobic natural processing. Considering that Flower Moon Night coffee beans use anaerobic natural processing, to preserve the fermentation sensation while showcasing full body thickness and flavor sweetness, FrontStreet Coffee's roasters use a medium roast approach.

After roasting, FrontStreet Coffee immediately conducted cupping. This Flower Moon Night coffee bean emits obvious berry and mature fruit aromas during grinding. The wet aroma after adding hot water is like rich strawberry jam. On entry, it's the sweet and sour of cranberry and strawberry jam, plus a strong fermentation sensation, just like eating liqueur-filled chocolate. After swallowing, faint floral notes remain in the mouth. To taste the poetic and picturesque aromas of Flower Moon Night, there are still details to pay attention to in brewing.

How to Brew Anaerobic Natural Coffee for Good Taste?

Since anaerobically processed coffee beans ferment for long periods in sealed spaces, the density of the bean cell walls decreases accordingly. Even though they are extremely hard beans from high-altitude Central American regions, the cell structure of anaerobically processed coffee beans becomes less compact, and the internal structure becomes looser after roasting. Therefore, water flows through more easily during brewing, the contact time between grounds and water shortens, and coffee can easily be under-extracted, resulting in lack of flavor. FrontStreet Coffee will make adjustments in grind size and pouring technique.

FrontStreet Coffee adjusts grind size using a tool—China No. 20 0.85mm standard sieve. For medium-light roast coffee beans, FrontStreet Coffee consistently uses a 75-80% sieve passing rate, while for medium-dark roast coffee beans, FrontStreet Coffee uses 70-75%. Here, the Colombian Flower Moon Night coffee beans use anaerobic-type fermentation, making the coffee beans' texture looser with better water absorption, and water passes through the coffee grounds more quickly, easily leading to under-extraction. Therefore, FrontStreet Coffee will adjust the grind to be finer, with stores using an EK43s grinder setting of 9.2-9.5.

Water temperature plays a similar role to grind size. The higher the water temperature, the higher the coffee extraction efficiency, making it easier to release various substances and resulting in higher concentration. If using near-boiling hot water for brewing, it's easy to extract unpleasant bitter substances. Therefore, FrontStreet Coffee recommends using 87-90°C for medium-dark roast coffee beans, while light roast coffee requires higher temperatures to stimulate aromas, thus using 91-93°C. FrontStreet Coffee suggests using 90°C to brew Flower Moon Night. This coffee leans toward a balanced sweet and sour, well-rounded profile. If using too high temperature water, it's easy to extract heavy bitterness, thereby masking various fruit and floral aromas.

The brewing dose remains 15g, with a coffee-to-water ratio of 1:15. A moderate concentration is more conducive to experiencing the various flavors of Flower Moon Night coffee.

Three-Stage Pouring Method:

First, place the folded filter paper in the dripper and wet it with water to make it fit better with the dripper. Prepare hot water and a thermometer, and pour 15 grams of ground coffee into the dripper at the same time, zeroing the electronic scale.

For the first stage, pour 30g of water for a 30-second bloom. Start timing while pouring, using a small water stream to pour from the center point outward in circles, ensuring the entire coffee bed is wetted. At this time, you can see the coffee grounds forming a dome as they release gas.

After 30 seconds, use a steady water stream to pour the second stage of 100g water, aiming to raise the entire coffee bed. The water column needs to be poured vertically and evenly. At this point, the scale shows 130g, completed in about 55 seconds. When the liquid level drops to nearly expose the coffee bed, start using a small water stream in small circles to pour the third stage of 95g. Try to control the water stream to not be too wide, and also try not to let the coffee liquid level exceed the powder wall formed by the second stage accumulation, as this can cause water to flow down along the filter paper, resulting in under-extraction.

Finally, the total amount of water poured is 225g, with a total drip completion time of approximately 1 minute 50 seconds. Remove the dripper and shake the coffee liquid in the sharing pot evenly before starting to taste. The flavor of hand-poured Flower Moon Night coffee: First comes the sweetness of strawberry jam and the fermented sensation of mature berries. After entry, the acidity of cranberry and berry juice sensation distribute throughout the mouth, followed immediately by a liqueur-filled chocolate-like aftertaste presented in the nasal cavity.

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