What is Wet Hulled Coffee? Learn About This Unique Process

Coffee drinkers worldwide have long understood that the process from bean to cup is a complicated one that can significantly influence the flavor of their morning jolt. Below, we explain the much lesser known wet hulled coffee processing, and how it imprints unique flavors to the coffee bean unlike any other coffee varieties.

In this post, we are going to explore what wet hulled coffee is, how it is processed, what type of difference the process makes in taste, and why this becoming one of the most respected processes in the coffee world.

Understanding Coffee Processing Methods

First let’s step back and look at what differentiates wet hulled coffee, so we can compare it to other coffee processing methods. The coffee bean is the seed of the fruit of coffee (A coffee ‘bean’ is technically a seed grown at the heart of a ripened coffee cherry). Once coffee cherries are picked, they require processing to remove the layers and yield green coffee beans to be roasted to make coffee.

There are two main types of coffee processes: washed (or wet) and natural (or dry). Both methods will influence the profile of the coffee beans: washed coffees generally have cleaner, brighter flavors, while natural coffees are more complex and fruity.

Wet hulling is an unusual hybrid process, employed primarily in selected coffee-producing countries, Indonesia in particular—particularly in Sumatra.

What is Wet Hulled Coffee?

Wet hulled coffee is a type of coffee processing between wet and dry processing. The method involves stripping the outer layers of the coffee cherry early on, but with an important variation. When the beans are hulled (have their parchment, or mucilage, removed) they’re left wet.

Wet-hulling is central to a type of Indonesian coffee farming, from the ancient to contemporary world. The outcome is that the coffee bean has its moisture locked in, providing a unique flavour that is in demand right now in the coffee market.

In this process, the coffee cherries are depulped to detached the outer skin and the beans are then washed to separate the mucilage. The beans are wet-hulled after being washed and have a high percentage of moisture. This precocious removal of the parchment skin is what distinguishes wet hulled coffee from washed coffee.

The Wet Hulling Process Step by Step

There are some steps of wet hulling process, such as:

1. Harvesting the Coffee Cherries

The process starts with ripe coffee cherries being picked. Usually the cherries are picked by hand so only the ripe fruit is selected. In wet hulling areas, like Sumatra, harvest is typically on a seasonal schedule to coincide with the cherries being at perfection.

2. Pulping the Cherries

After the cherries are picked, the next step is pulping. In the case of wet hulling (for reasons I’m about to explain), this means removing the cherry flesh off you-know-what.

There are mechanical pulping machines or hand pulping machines, which remove the skin and pulp of the cherry, leaving the beans covered in mucilage – a sticky, sugary substance.

3. Washing and Fermentation

Following pulping, the beans are washed to eliminate the mucilage. This is an important classifying stage in the wet hulling process.

The beans may be fermented to loosen mucilage further. The beans are then washed well in time for the next process.

4. Drying the Beans

The next stage is drying but this is where wet hulling starts to deviate from the wet processing norm. Instead of drying the beans wet, and to a moisture content of around 30-40%. Washed coffees, like 54, are usually dried to the 10-12% moisture content level.

5. Hulling the Beans

The beans are then dehulled while still relatively moist. And this one took off the coffee’s parchment layer. Hulling damp beans is a difficult process and calls for machinery with high bearing requirements to handle higher moisture content while not crushing the beans.

6. Drying Again

Once the beans have been hulled, they are laid out to dry more. Here, the beans are sun-dried or dried mechanically. The moisture is decreased gradually to 12%, which is the best rate for storing and roasting.

7. Sorting and Grading

After the beans are completely dry, they are cupped and graded. Wet hulled coffees are hand sorted and graded for size, shape, and color. Defective beans are also detrashed to ensure the final quality of the product.

Read also: How the Luwak Coffee Process Works

Why is Wet Hulling Done?

Wet hulling is done for many reasons but one of the big ones is the environment in which wet hulling is done. In Indonesia, where it is very humid and rains significantly, drying the beans can be challenging with the usual techniques.

By leaving the beans moist and hulling them earlier in the process, farmers can avoid the risk of mold and spoilage that could occur if the beans were left to dry for extended periods in these wet conditions.

Another reason wet hulling is done is because the process contributes to a distinctive flavor of the coffee beans. The water content is beans during hulling influences the chemical reactions in beans to produce characteristic flavor compounds. This produces coffee with the fuller body, earthy and, at times, spicy as well as lower acidity compared to washed coffees.

The Unique Flavor Profile of Wet Hulled Coffee

One of the reasons customers and roasters love wet hulled coffee is the distinctive flavour profile that it gives. Note, depending on the region or specific beans used, the flavor may vary slightly but in general you can expect wet hulled coffee to have:

• Earthy: Wet hulled coffees tend to be fairly vegetal and musty tasting, which is what distinguishes them from the brighter, more acidic flavors of washed coffees.
• Full-bodied: These are heavier in the mouth with more body in these coffees. Wet hulled coffee has a thick and heavy texture, making it a favorite for those who like their coffee strong.
• Spicy: A lot of wet hulled coffees have a spicy note to them (cloves and pepper) which gives it even more dimension and character.
• Low acidity: Wet hulled coffees tend to be lower in acidity compared to their washed coffee counterpart. These beans are less acidic, making them the perfect option for those who can’t handle that kick anymore.
• Herbal and woody notes: Wet hulled coffees can take on an herbal, woody or even tobaccoey flavor, depending on the region. Of these flavors, they contribute complexity to the cup as a whole.

Where is Wet Hulled Coffee Produced?

Wet hulling is mostly synonymous with Indonesia, and in particular Sumatra, though it can be found elsewhere in South East Asia and beyond. The climate of these regions also renders the wet hulling process really appropriate for the situation.

Indonesia

In Indonesia wet hulling is a traditional processing method used to process coffee beans in Sumatra, Bali, and Sulawesi. The most well-known coffee these days processed in this way is Sumatran Mandheling; arguably the earthiest and spiciest coffee in the world.

It is best suited to the wet hulling process in Sumatra’s wet climate with high humidity and frequent rain, so that the beans do not dry too fast.

Other Regions

Wet hulling is also practiced in other coffee producing countries, Papua New Guinea, Timor, and parts of Malaysia as well. The climate and environment in these origins are similar to the climate in Indonesia thus wet hulling is a good practice for local farmers.

The Impact of Wet Hulling on Coffee Quality

Wet hulled coffee can be a good product, but the quality can vary from one area to another, one farmer to another, or based on the overall processing. And, generally, wet hulled coffee is bolder and more complex than it’s processed by other processes, though the quality can differ.

Some farmers carefully hull and dry the beans, and you’ll drink fine in the flavors there. Wet hulling gets its name from the fact that beans are not completely dried out (like is typically done for other forms of processing) and are therefore at risk for mold or spoilage if not appropriately handled.

Wet Hulled Coffee and Sustainability

More recently the environmental impact of coffee production has received more attention and the practice of wet hulling is under review in this context. And although the process is not inherently damaging to the environment, it is incumbent upon producers to dispose of waste products in a way that won’t harm the environment.

In some context, wet hulling is as much a sustainability argument as it is anything else. For instance, some coffee growers are collaborating with organizations to make the wet hulling process more efficient, minimize waste, and make coffee growing more eco-friendly.

Conclusion

Wet hulling coffee is a complex and interesting process that gives the beans their enjoyable flavors. This method (known only in Indonesia) produces a thick, rich and syrupy cup that is one of the boldest in the world.

For the seasoned coffee drinker or novice speciality drinker, and experience tasting a wet hulled coffee is enlightening and may expand your palate to new taste sensations.

References:

• Wet Hulling Coffee: What You Need to Know – Perfect Daily Grind
• A Guide to Wet Hulling Coffee – CoffeeReview
• The Coffee Processing Methods: A Comprehensive Guide – Atlas Coffee
• How Wet Hulling Affects Coffee Flavor – The Coffee Collective