What are the advantages and disadvantages of wet hulling process for coffee beans? The relationship between wet hulling and defective elephant foot beans

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The Love-Hate Relationship with Gayo Mountain Mandheling

The Lake Tawar Gayo Mountain Mandheling from Aceh Province, Indonesia, has always been a coffee that I deeply love yet find somewhat annoying. Friends who have encountered Mandheling series green beans should know more or less that Mandheling green beans have a special characteristic: vibrant green, clear, with little silver skin, full and juicy, strong beans that make you unable to resist being deeply attracted at first sight... and then your wallet unconsciously loses a few bills... XD But I must say, that's only after undergoing rigorous hand-sorting.

The first time I bought this Gayo bean, I didn't do my homework properly. Because I had long heard of Gayo's fullness and vibrant green color, and the beans in pictures all looked delicious, I was full of anticipation to receive perfect, full green beans. The result was that when I received the beans, I immediately called the bean supplier to argue with them!

Mandheling - Mixed Defective Beans

▲ Mandheling beans filled with many elephant beans, hulling machine bite marks, doubly terrifying insect-damaged beans, black beans, crushed beans, cracked beans, etc. I can't help but appeal to friends again! If you drink this kind of stuff, it would be strange not to have palpitations, insomnia, or discomfort!

Spectacular Color

▲ But the terrifying reward of defective beans is that the sorted normal beans become even more brilliant and beautiful!

Sumatra Gayo Mandheling

▲ Roasted from selected beans ^^

When I received the beans and saw them, I was stunned - how could they be like this?! Without understanding the situation, thinking the supplier had given me a bag of defective beans, I immediately called to argue with the supplier. The argument got so heated that the supplier angrily hung up on me, making me very angry and even deciding to process a return and refund. However, I didn't want to return the beans without understanding the situation clearly, and I was afraid that my own limited knowledge might wrong the supplier, so before processing the return, I asked a senior roaster about Mandheling's characteristics. Only then did I learn that strange beans like elephant beans and scratched ones are actually commonplace in Mandheling - completely normal. I had truly wronged the supplier, so I wrote an email to apologize, and after carefully sorting through the beans, I trial-roasted them, and have loved Mandheling ever since.

Although Mandheling green beans may seem to have many defective beans, after sorting to the end, I discovered that while the proportion is indeed higher than general estate beans or specialty beans, and visually terrifying when you first open the bag, most of it's the "showy" strange appearance of elephant beans, plus the visual magnification of Mandheling-specific defective appearances like scratched beans. Actually, after quickly removing the truly terrifying black beans and dark insect-damaged beans, it's not as unbearable as when first opened. However, my habit remains: if I'm going to do it, I want the best, so spending a whole day "one by one" picking up beans from the sorting tray, examining them to confirm zero or extremely minimal defects, then separately packaging them into half-pound portions for storage, is essential work every time I purchase Mandheling. Although it's truly exhausting, it's worth it for that clear, sweet, delicious flavor.

The reason why Mandheling has so many strangely shaped beans, even making people wonder "Is this bean supplier a scammer!?" was finally found in the recently published book "Fine Coffee Science." To understand Mandheling's appearance issues, we must start with its processing method. (The following is my reinterpretation and organization of Mr. Han Huaizong's introduction)

In Mandheling's origin: Sumatra, Indonesia, is a very humid region. Generally, coffee green bean processing is done after drying is complete, when moisture content drops to 12% or after one to three months of aging in storage, then the husk is removed to extract the coffee beans we're familiar with. However, because Sumatra is too humid, the wise local ancestors developed a unique technique: Wet-Hulling, which means removing the husk when the green beans are only half-dried, still with moisture content as high as 30%-50%, then continuing to let them dry to solve the dilemma of overly long drying times. This method shortens drying time to only two to four days, reducing the coffee's fermentation period, significantly lowering acidity, while increasing body, with distinct caramel and fruit aromas, even carrying herbal or grassy scents and woody notes - these are Sumatra's unique regional special fragrances.

However, the impact of early husk removal is that the green beans lose their last two protective layers halfway through drying (note: coffee beans' four protective layers: pulp, pectin, husk, silver skin), equivalent to sunbathing without clothes. Although the wet-hulling method solves the drying time problem, the probability of green beans being contaminated by mold, fungi, and yeast increases significantly. But paradoxically, these factors actually become key to creating Mandheling's special aroma...

Another characteristic brought by wet-hulling is the higher probability of so-called "elephant beans." Because the husking machine removes the husk when the green beans are still moist and in a semi-soft stage, the fragile, soft, wet green beans are very easily damaged by mechanical pressure, cracking, breaking, or scratching the bean surface, forming so-called elephant beans and scratched beans, making the green beans' appearance poor. This is why commercial Mandheling green beans always look messy - even those claimed to be G1 grade, triple hand-sorted, are the same, even making people suspect they've encountered an unscrupulous supplier. But after careful hand-sorting, the resulting green beans are more crystal clear than common green beans, which is also why Mandheling makes me both love and somewhat hate it.

Mandheling beans cannot be completely judged by traditional specialty coffee's defective bean standards, but as long as you carefully sort, removing heavily defective insect-damaged, black, and rotten beans, the beans after defect removal are basically usable - it just depends on how thoroughly you want to sort. Personally, I treat beans like works of art, so I select them to zero defects. Basically, you don't need to be like me.

FrontStreet Coffee: A roastery in Guangzhou with a small shop but diverse bean varieties, where you can find various famous and lesser-known beans, also providing online shop services. https://shop104210103.taobao.com

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