How to Write Wet Hulling in English: Coffee Bean Wet Hulling Method - Giling Basah or Wet Hulling?

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Wet Hulling

This is a coffee processing method exclusive to Indonesia and surrounding coffee-producing countries. Giling Basah is Indonesian, literally translated as "scraping off the hard shell under wet conditions." It also has another English name called Wet Hulling.

The earliest domestic translation of this term appeared in Teacher Huan Huai-zong's book "Specialty Coffee Studies." I personally believe that Teacher Huan's translation of "wet hulling" is the best understanding of this processing method. Other incorrect naming, such as the most typical "Semi-Washed," confuses several coffee processing methods, causing a group of coffee people to have almost zero understanding of wet hulling, which is lamentable. Believe me, you will never see these three words "semi-washed" again in our description of processing methods.

The significance of wet hulling to the global coffee industry is no less than that of honey processing. The "Mandheling," which every coffee enthusiast must try when starting out, is processed using this method. It can even be said that the vast majority of Arabica coffee in Sumatra and Sulawesi, Indonesia, uses wet hulling. According to 2014 International Coffee Organization (ICO) statistics, Indonesia is the world's fourth-largest coffee-producing country. A processing method that contributes so much to global coffee production must be worth our research and analysis.

Coffee Cherry Structure

Before getting to the main topic, we need to understand the nature of coffee beans.

First, botanically speaking, coffee beans are not "beans." Coffee fruits belong to fruits. Indeed, they look very much like beans, but from the fruit形态 of the coffee plant, coffee fruits are more like peaches than beans. What we usually call "coffee beans" are the seeds of the coffee plant.

In other words, the coffee beans we usually see have four layers of material outside: silver skin, parchment/endocarp, mesocarp/pulp & mucilage, and exocarp/red or yellow skin.

Why do people, regardless of nationality, mistakenly call coffee beans? Mainly because people tend to ignore the pulp part of coffee cherries. The pulp of coffee cherries is really too thin. Below are cross-sections of coffee cherries and peaches.

In our daily lives, when we eat peaches, we eat their pulp; when we enjoy coffee, we roast their seeds, grind them, and brew them with water. All other skins and pulp are discarded. Plus, coffee seeds look very much like beans, so everyone naturally calls them coffee beans. In future descriptions, for simplicity and ease of understanding, we will still use the term "coffee beans," but everyone needs to understand that coffee beans are not beans.

What is the significance of processing methods? Coffee cherries grow on trees. When coffee farmers pick them, they look like this.

At this point, the coffee cherries are still fruits, and their moisture content is still quite high. Coupled with the sugar contained in coffee pulp, if they are piled together for a long time, they can easily lead to fermentation, mold, various bad flavors, and even food safety issues.

Therefore, people need to find ways to convert coffee cherries that are not suitable for long-distance transportation and storage into something stable and not easily perishable. The idea is to remove the skin, pulp, and parchment of coffee cherries, and then dry the seeds.

Steps

Whether in small coffee farms or slightly larger coffee estates, all coffee in Indonesia is hand-picked. After picking, there is the routine soaking to see sinking and floating for rough screening: the sinking coffee cherries are kept, while floating debris and green fruits are screened out.

The mature red cherries are now put into a depulping machine to remove the skin. Unlike the washed method, wet hulling uses smaller depulping machines. These machines are so small that almost every coffee farmer can afford one, so the "depulping" stage is almost entirely completed at the farm level.

The next two pictures show aunties and uncles using machines to scrape the fruit skin. The hardworking coffee people are always so beautiful and handsome.

Next comes fermentation. In the washed method, fermentation involves putting depulped coffee beans with mucilage into fermentation tanks to soak, using bacteria to remove the mucilage. This process lasts about 24-48 hours, with the water quality in the soaking tank roughly equal to the quality of the beans. Wet hulling fermentation is slightly different: fermentation is only 12 hours, very little water is used, and it often takes place in smaller containers, such as plastic basins or even plastic bags. After this brief fermentation, most of the mucilage attached to the parchment can be easily rinsed off, with a small amount of mucilage remaining on the parchment. This step is also completed at the coffee farm level.

Coffee farmers bag the wet and sticky coffee parchment and transport them to weekly gatherings of agricultural markets to sell to others, often buyers from processing stations. The purchasing unit calculates by volume, with locally pre-measured dedicated buckets—one bucket marked as one liter or two liters—and pays coffee farmers at a price of XX yuan per liter of coffee beans. Buyers often pay in tiers based on observing the amount of residual mucilage attached to the parchment. More residue means lower price; less residue means higher price. The picture below shows a dedicated one-liter measuring bucket "a litera can."

After processing stations collect many, many wet parchment beans, they directly send the still-un dried parchment beans (35%—45% moisture content) into the hulling machine to scrape off both the parchment and the mucilage attached to it. This is the so-called "wet hulling." This step is different from all other processing methods. Whether washed, natural, or honey processing, all dry the parchment beans (11% moisture content) before "dry hulling" to remove the parchment.

Wet Hulling Coffee Bean Hulling Also Has Its Tricks

The picture above shows a dedicated hulling machine for Indonesian wet hulling. In terms of size alone, it is three times the size of a washed hulling machine. More important than size is the nature of the grinding core. The picture below shows freshly hulled wet-hulled green beans, which are very moist.

The surface of wet green beans appears white and is slightly swollen. Such green beans are very soft. If using the internal metal grinding core hulling machine of the washed method, the beans would quickly be ground to pieces. An American processor once tried this out of curiosity. "Only about one-tenth of the beans were whole," the American cried. Indonesians therefore have their own modified version of hulling machines. To accommodate the swollen beans, not only is the caliber wider, but they also use softer, high-friction plastic grinding cores. Although there are still many broken beans due to the fragility of the green beans, the situation has greatly improved compared to using washed grinders.

The first picture shows a cross-section of washed dried parchment beans, and the second picture shows a cross-section of wet-hulled, very high moisture content parchment beans. As you can see, the parchment of wet hulling is still soft at this time, while the parchment of the washed method has become brittle and dry after being blessed by the hot sun. During the drying process of the washed method, after the green beans inside the parchment lose moisture, their volume decreases relatively, and there is a very obvious gap between the green beans and the parchment. However, the wet-hulled parchment beans do not have such an obvious gap inside, and the beans are very swollen. The two points described above make the step of hulling the parchment in wet hulling increasingly difficult, and the number of broken fragments caused by intense friction in wet hulling is also quite high.

At this time, the exposed green beans with still high moisture content are spread out on cement ground covered with straw mats or plastic sheets for drying. Although there is no easily perishable organic matter like mucilage on the bean surface, coffee workers still need to pay attention to turning the beans frequently. After all, with such high humidity, plus the directly exposed green beans being very fragile, they can rot if left covered.

Theoretically, wet hulling drying is faster due to the lack of "sealing" from parchment. This is not the case. People in the coffee industry describe Sumatra's drying process as a "nightmare." Indonesian Sumatra is truly one of the few coffee-producing regions with very humid climates. According to a coffee person who has visited Indonesian producing areas, "the longest drying time within a day is 4 hours—taken out in the morning and brought back in the afternoon when it rains heavily." Some slightly wealthier coffee processing workshops set up greenhouses! Drying in the shed might save more costs than taking them in and out.

The humid weather also brings great trouble to coffee picking. In producing countries with clear and stable weather patterns, such as Central America, coffee pickers go to the fields an average of 3 times to pick all coffee cherries. For Sumatra, which doesn't know what weather distribution is, coffee pickers need to go to the fields countless times over the entire 6-month period when coffee cherries mature. Why? Because coffee trees flower and fruit according to the weather! If the weather is stupid, then the coffee trees will be completely confused.

Under such harsh conditions, drying the green beans takes about half a month, with the specific number of days depending on luck. The big brother from Counter Culture Coffee, and SCAA President Peter Giuliano believe that due to the lack of parchment, plus the freshly hulled green beans being moist and warm, and Indonesians not using raised beds for drying, the green beans can be influenced by many external enzymes and microorganisms, especially those from the ground. Perhaps it is due to these factors during the drying stage that Sumatra coffee generally carries a "earthy" odor/aroma (judge for yourself).

The left side of the picture above shows freshly hulled green beans, appearing white and larger; the right side shows dried green beans, appearing dark green and smaller. Common characteristic: an insanely high rate of defective beans.

The drying of exposed green beans gives wet-hulled green beans a common characteristic: a forest green color.

Among the beans, why is Mandheling's head green!

The introduction of wet-hulled coffee bean processing ends here.

Evaluation

To be fair, without blowing or dissing, if you put a medium-quality Mandheling and a bunch of medium-quality Central American beans together for cupping, the first one to be shot is often Mandheling. Its flavor characteristics don't seem to align with our accustomed evaluation standards. Wet hulling flavor is one of the most heated debates in the specialty coffee world—some treasure it, others wish they could spit on it.

I dare to summarize the flavor of wet hulling. Apart from those subtle differences, we generally believe that wet-hulled beans carry earthy, smoky, and chocolate flavors, with acidity described as "low acid," appearing quite dull. Using synesthesia, the editor would say: drinking wet-hulled coffee is like having a dark cloud covering your heart for a long time without dispersing.

The low acidity comes from the shorter, less effective fermentation process and longer drying time. If you forgot about wet hulling fermentation, go back and look. As for the "earthy" flavors of wet-hulled beans, opinions vary. Some say it's related to the bean varieties used in wet-hulling-related producing areas (Timor & Catimor varieties: with Robusta heritage), some say it's the result of organic interactions between green beans and the external environment (Peter Giuliano), and some even say it's because there are too many defective beans! Of course, there are quite a few...

There are many sources of defective beans in wet hulling. First, natural defects from the coffee cherries are inevitable, and another contributor to defects is the hulling part, plus corrosion during the transportation of wet parchment beans, damage to exposed green beans from sunlight and humidity, and additionally, the uneven drying speed caused by irregular weather also detracts from the flavor. Why does Mandheling require so many hand-sortings? Of course, there's a reason...

I emphasize that those who don't distinguish between washed and wet hulling are being deceptive, because as you can see yourselves, although there's not much difference in names: Semi-Washed & Washed, Semi-Washed is still an incorrect name. But the detailed steps of the processing methods and the flavor impacts brought by these operations are worlds apart. Whoever says Mandheling is washed again, wait at the school gate, I promise not to beat you to death.

Indonesian beans have always been an indispensable element in blended coffee. Its low acidity and rich chocolate aroma are very suitable for mixing with milk. The second wave of coffee brought by Peet's old man stood on the shoulders of Sumatra wet-hulled low-acid, thick coffee. Combined with his unique dark roast, it perfectly demonstrated the correct way to interpret Sumatra coffee. Although Starbucks is increasingly straying from the path now, who can deny the importance of Sumatra wet hulling?

After a wave of praise, let's have a wave of criticism. The so-called G1 Mandheling is basically useless. The 33% defect rate is still there. Not to mention several sortings at the producing area before export, just as the editor has seen, green beans are hand-sorted once when they reach the coffee roaster, sorted again after roasting, sold to shops, and shops even sort them again! Some have proposed a new theory for dark-roasted Sumatra: damn dark roasting covers wet hulling defects! Indeed, this cannot be denied. The past and future of Sumatra coffee still have many uncertainties. As we said before, on the cupping table, Sumatra often dies the most miserably because it doesn't fit our general standards for specialty single-origin coffee.

We should also have confidence in Sumatra. In recent years, the Indonesian Specialty Coffee Association (SCAI) has been established, quality supervision in the coffee production chain has been strengthened, and some producing areas and estates have introduced partial washing mechanisms. Some producing areas have begun to embark on the path of high-quality, high-supervision characteristic wet hulling. Regardless, the editor remains optimistic about the coffee development in Sumatra, Indonesia. I don't want such a large and important producing country to continue with an unclear burden. I believe it still has much room for improvement.

Wet hulling and related knowledge points about wet-hulled coffee beans end here.

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