Coffee Fermentation: Understanding Dry vs Wet Coffee Process

Coffee, I was once surprised to learn, is not a bean in any proper sense. Wikipedia tells us the beverage is “a brewed drink prepared from roasted coffee beans, the seeds of berries from certain Coffea species.” Today, we’ll cover why the fact the coffee fruit is dried onto or wet-processed off the coffee bean has a big impact on the flavor of your final cup. Washed vs natural coffee might seem like a mystery now—it did to me at first, too.

As I’ve learned more about coffee, I’ve learned that my sweet tooth really appreciates “dry-process” or “natural process” coffees. These are generally contrasted with “wet-process” or “washed process” coffee. This dry process vs wet process distinction will really have an impact on how “fruity” vs “classic” the flavor profile of the coffee in your cup will be. But just so we’re clear, “washed coffee” doesn’t mean it’s “clean,” but how it was processed. It makes a noticeable difference in the cup you drink, so we wanted to inform our audience (as best we can) Onward to real learning!

Basics of Coffee Production

To be effective, I’ll vastly oversimplify the work thousands of that people do regularly with expert skill. Coffee making is a process humans have spent hundreds of years improving, too. No matter. The production process for coffee in comically short form goes through approximately the following five steps…

5 steps to making coffee, from start to finish

  1. A coffea “tree” is planted, and nourished. Eventually it grows to a size where it can bear fruit.
  2. Once it has born and ripened “cherries”, the berries of the plant are harvested.
  3. The “coffee bean” we want, the cherry pit, in effect, must be separated from the fruit. When and how this is done is the difference of dry vs wet (vs honey) coffee processes.
  4. Coffee is roasted to perfection.
  5. You brew your (more lightly) roasted coffee beans, and you discover the difference that dry vs wet coffee process makes in the final coffee drink.

Coffee is Grown; We’re drinking the “cherry pit”

I just want to reemphasize the point in parts 1 & 2 above: whether from wet or dry processes, coffee “bean” are not botanically beans at all. (It’s very like how “peanut” are botanically not nuts, and tomatoes are botanically fruits.)

The other thing that’s relevant but I know a lot less about is that in this stage of coffee production, you have different types of coffee plants. “Arabica” coffee and “Robusta” coffee are actually just varieties of coffee plants. In general, robusta is more mass-produced, and grow at lower elevations, where Arabica grows higher and is generally preferred by snobs like us.

Even more, I’ve heard a lot about “bourbon” (pronounced as if French “bore bone”, not like the corn-whiskey made here in the USA “bur bun”) coffee. Bourbon coffee originated in Yemen, and is simply a variety (“cultivar”) of the Arabica variety. Similarly, Gesha or Geisha coffee is a plant variety. But I’m very off topic, let’s get to what happens after the coffee plant (of whatever type) is harvested: the processing.

A Rundown on the Main Coffee Processing Methods

What are the three coffee processing methods? Onward to coffee fermentation process 101.

Method 1: After Harvest, Wash That Fruit Away (Washed Process Coffee)

Coffee beans on drying racks
“Coffee Farms and Processing, Kerinci, Sumatra, Indonesia” by Wild Sumatra https://www.wildsumatra.com is licensed under CC BY-NC-SA 2.0

Wet process coffee beans seem to be by far the most common. If you think of “traditional” coffee, there’s a high probability that you’re thinking of washed-process coffee. Further, because this method basically gives you the flavor of the bean-only, and you get no input from the drying method, you’ll often get a clearer sense of bean itself, and the “terroir” of its growth.

Conditions for drying will impact whether producers end up washing the fruit away quickly, or letting it sit on the bean. A producer trying to dry process can harm the integrity of the beans inside (they’ll split, and thus make consistent roasting much more difficult) if the conditions are too humid. So, high humidity or rains when the coffee would dry mean they must follow the coffee processing steps to wash/wet process their bean and separate the fruit off ASAP. 

The wash-process, as the name suggests, is where you pull the ripe fruit off the bean as soon as you can, and get the beans wet. That’s why it’s often called either “wet” or “washed” process. You’re generally pulling off the fruit in a water-y system, and often get the beans a little “wet” as a result. I saw someone explain this separation process of pit-from-fruit as a squeeze of the fruit so it “spits out” the bean. Again, I’m sure that’s a vast oversimplification of complex machinery people have worked on for years. In any case, once extracted we wash the bean to get rid of the spit, or the sticky residue of the fruit. Whether or not this “spitting” analogy is accurate, it sure sticks with me.

Method 2: After Harvest, Dry Fruit upon the Pit (Natural Dry Processed Coffee)

In short (I’m sure experts can add nuance to this), dry process is where the fruit is left in tact while the bean dries out in the sun. Only after this “aging” has happened to the coffee for a few days or weeks will the bean be removed. So, for longer after ripening for harvest, the bean and fruit co-mingle their molecules.

This gives, as you might expect, a greater transfer of flavor from the fruit of the cherry to the “coffee bean” pit inside. Because this sitting-together can help with the removal of the berry, this is also the oldest method of processing coffee. Dry-process requires less industrial equipment and clever gadgets than “washed process” coffee does, but it also works in a less diverse array of conditions. Primarily, the surrounding air must be at a good humidity level (a wet season can make this go wrong). And chronically-wet areas means its just plain impossible to dry-process coffee in certain countries.

We’ll go into more tasting details later on. But suffice it to say that while beans vary hugely between origin and producer, you’ll notice similar trends in flavor notes of all dry process coffee vs other methods. And they’ll generally be fruitier: citrus, blueberry, and more. Again, because of the longer sit-together of fruit-and-bean, this makes perfect sense.

Method 3: After Harvest, Pulp the Coffee Beans & Let Them Sit (Honey Process Coffee)

So far I’ve mostly talked about wet-vs-dry coffee-process. But there is actual a common third coffee processing methods. Wait?! Three? I actually just recently discovered this fact in a marketing email from Blue Bottle, a large artisinal American coffee chain now owned by Nestle, about “honey process coffee.”

Thinking mostly in terms of the dry-vs-wet dichotomy I understood, I was intrigued. They claim that is it indeed a third process, and I believe them. The core idea of honey process coffee is that it’s a mid-point between wet and dry process. Neither is the whole fruit-layer left on, nor is it expertly removed fully in a water bath. Instead some fruit-residue intentionally remains (often, unappetizingly called the “mucilage” in English), which can then dry into the beans to give them a honey-like look.

Then, rather sun-drying the remaining “pulped” coffee bean, the processor will also make sure to safeguard the coffee from the sun, at least a little. This is in contrast to the sun-soaked methods most common for natural process coffees. I found this video from Amber at Seattle Coffee Gear very well-done and super informative on the matter of “honey process” coffees:

*Ahem*—Sun-dried Coffee Beans?

While researching this article I was a little like “oh, what’s sun-dried coffee?” It turns out it’s not really a different processing system (like honey process), but just one more on the list of names for “natural” and dry process coffee. In this article from Counter Culture, they state it pretty plainly:

Natural process, dry process, unwashed, or natural sundried all refer to the same method of processing that usually involves drying coffee cherries either patios or raised beds in the sun.

They go on to point out the value of raking and turning the beans strategically during the coffee fermentation process, in addition to dry weather, that is necessary for the natural-process method of coffee processing to work. Again, making this a simple dichotomy is both useful but hiding complexity and expertise.

Which Tastes Better: Natural or Washed Process Coffee?

By now (if you’ve read thoroughly) you’ve picked up on my theme that “sun-dried natural process” coffees are “fruitier” in flavor than wet or washed process ones. In my very limited experience, I’d say that honey-process coffees are a little closer to the fruity end than most “washed process” ones.

When it comes to washed vs unwashed coffee beans, I’d generally expect “nutty” flavors from washed process coffee. You’ll also pick up things more like “maple,” “caramel,” “chocolate,” or “spice.” But if you have a cup of coffee and think, “is this blueberry tea?”, you should put your money on it being a natural-process coffee with the fruit dried onto that bean.

Because of how different coffees are (and my relatively lack of experience on the matter of what makes some coffee taste better to me than others), I won’t belabor the point about coffee bean processing methods and taste preferences much more. I’ll cite instead (from the Counter Culture article mentioned above) the claim that sun-dried dry-process coffees are also “more fruity and fuller-bodied. The natural sugars in and around the seed are infused into it during this process and result in a higher sugar content than washed coffees.” This certainly matches my experience, and explains why I like them so much. So for me, in the case of washed vs natural coffee, natural almost always wins.

Which Coffee Processing Methods Should You Pick?

Both! Or even all three! I don’t think there’s a “right” answer between washed-process coffees and dry-process ones. Two of my favorite coffees right now are from local Colorado roasters. One is a straight-forward delicious Guatemala from Harbinger. (I need to buy this again soon!) That’s the best of what I think of as “classic” coffee flavors. My other favorite is a natural process from Sweet Bloom (currently gone from stock and not shown on the web), for which the available Nyamasheke from Harbinger comes the closest of what I know you’ll be able to get. Both are very good. Cheers! 🙂

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