Indonesia is every sort of wet and always all kinds of “Basah.” Rain? Plenty of it, more than most places on earth.
Humidity? Oh, heck yeah. Humidity will often reach well above 90% throughout most of Indonesia. Ocean? Everywhere.
Everywhere, there is ocean. That brings us to wet hulled coffee.
The History of Wet Hulled Coffee
The story behind “Giling Basah” (grind or mill wet) coffee is, from start to finish, a story about moisture. Although you
might hear tell that wet hulled coffee is a processing expediency related to cash flow, the fact that producers can
be paid sooner rather than later for wet hulled coffee is simply a reality that coincides with the necessity of
battling the relentless presence of moisture and the impracticability—economic, logistic, structural—of drying
coffee efficiently in that environment, combined with the prevalence of smallholder farmers. The story goes like
Let’s say you are a small coffee farmer in Sulawesi (though you could
be in Flores, Sumatra, Java, or even Laos). Like nine out of 10
coffee farmers in Sulawesi you grow coffee on less than 1 hectare of land. Like your coffee farming neighbors, you
don’t have access to a coffee mill or production facility of any kind other than a small, shared, hand-cranked
pulper manufactured long ago by E. H. Bentall and Co. that has been rebuilt and repainted many times over the
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Founded in 1805, E.H. Bentall & Co., of England,
began manufacturing plows and was known for innovative design. By WWI the company had expanded into
manufacturing all kinds of farming implements, including a wide variety of milling equipment. Following
WWII, the company found a significant growth niche manufacturing coffee processing machinery. Bentall was
acquired by a company named Acrow in 1961, but the Bentall brand remained. Acrow closed its doors in 1984,
so when you see small milling equipment, like these Bentall pulpers in Sulawesi, they are at least 40 years
old and possibly much older. Photo by Olam.
After you harvest coffee cherries you run them through the hand pulper, spinning a cylindrical “cheese grater” that
removes the outer skin and the bulk of the flesh of the cherry, or pulp. But this leaves a layer of fruitiness, the
“mucilage,” or, if you're the kind of person who uses a lot of starch in your lab coat, what you might call the
“pectin.” To break down that pesky pectin, you soak the sticky coffee in water overnight inside … well, whatever you
have, from bags to buckets. This is fermentation and it makes it easier to wash off the mucilage to get to the clean
After pulping the mucilage remains, so the coffee is
fermented overnight to make it easier to remove.Photo by Olam.
The Difference between Wet Processing and Wet Hulled Coffee
But wait, you say, this sounds like wet-processing. But wait, I reply, yes it does, but I’m not finished. At this
point you have wet parchment coffee. We need the green bean inside the parchment to lose some of its “water weight”
because then it will be easier to remove the parchment. This means drying the coffee because as the green coffee
bean inside the parchments loses moisture it shrinks and separates from the parchment, making it easier to remove.
The difference between wet processed coffee and wet hulled coffee is how we get from point A (wet parchment) to
point B (dry green coffee).
mucilage is washed off you dry the parchment wherever you can to get the moisture content down to 50%. Photo by
In wet processing, or washed coffee, the wet parchment now begins a lengthy drying process, a distance measured in
moisture but not necessarily time. Wet parchment will have a moisture content well above 50% and it needs to be in
the neighborhood of 11% to remove the dry parchment after it has separated from the bean. This is accomplished by
drying the coffee in parchment on patios or mechanical dryers or a combination.
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You don’t have a drying patio. Even if you did, between rain and relentless humidity, it would take a long time to
get coffee down to 11-13% moisture for dry hulling. So, you spread the coffee out as best you can, wherever you can,
to get the moisture content closer to 50%. The time can vary from one to several hours depending on circumstances.
collectors buy coffee from farmers and then sell to the mill at the same price per standard size can. The
difference is, when they buy the coffee, they buy a heaping can full (like a heaping spoonful), but when they
sell the coffee they sell a level can. That tiny hill of coffee on each can is their profit. Photo by
Selling & Processing Wet Hulled Coffee
After this brief period of drying you take your coffee into town on market day and sell it to a buyer or “collector.”
If your coffee isn’t too wet and it’s clean of mucilage, you’ll get a better price than otherwise.The collector has
the means to transport coffee to a mill with a “wet hulling” machine. They wait for the coffee to lose another 20%
moisture, give or take, but even so the parchment remains tightly adhered to the bean.
A wet huller is a large milling machine designed to apply the extra friction required to remove parchment that is
still, relatively speaking, damp, and doesn’t want to go anywhere. A wet huller works on the same principle as a dry
parchment huller except it applies great friction and is designed to operate in a much wetter environment, drawing
off water in addition to parchment. Imagine you are removing leaves from your driveway with a leaf blower. Now
imagine how much easier it is to remove dry leaves than it is to remove wet leaves and you have some idea of the
difference between dry hulling and wet hulling. Finally, after wet hulling, the green coffee is laid out to dry, but
without the parchment it dries much faster. As a result, your coffee can go from picking to shipping in around a
month; whereas, in most coffee growing regions this takes several months.
Wet-huller. Photo by
This process can be abbreviated, usually depending on geography (i.e. the farmer might sell directly to a mill) or
elongated (i.e. there might be more "middle-people" between the farmer and the mill). Wet hulling can be more
unforgiving than other processing methods but can also provide opportunities to deliver the best of traditional
Indonesian profiles without the negative aspects sometimes associated with poor quality. Wet hulling emphasizes body
over brightness, and savory over sugary sweetness. Because the final drying is done without the protection of
parchment, care must be taken in the drying environment. Mills with an eye on improving quality use raised, screen
beds in greenhouse-like structures to protect the green coffee and to keep the moisture content from creeping back
Greenhouses for drying
coffee at both the parchment phase and green are more common as producers focus on improving quality while
maintaining the positive flavor attributes for which Indonesian coffees are known.