Why Coffee Beans Have Wrinkles: Roast Levels, Processing Methods, and Bean Structure Explained

 I don’t know if you’ve ever really taken a close look at the coffee beans you brew every day. Some beans have lots of wrinkles on the surface, while others look surprisingly smooth. So what actually causes that difference? Today, let’s talk a little about it — just enough to give you some fun coffee trivia to chat about with your barista, haha.

These wrinkles are actually caused by a kind of “shell collapse” that happens when the internal structure of the coffee bean goes through dramatic physical changes. Green coffee beans contain moisture and dense plant cell structures. During roasting, as the temperature rises, the water inside turns into steam, pressure builds up, and the gases try to escape outward. At the same time, structural materials like cellulose and lignin begin to soften and become more brittle under high heat.

After roasting, when the beans cool down, the remaining moisture and the carbon dioxide produced during roasting continue to slowly release from the bean. The cell walls that were once expanded by gas pressure begin to collapse as moisture and gas escape. Since the outer surface of the bean is less flexible than the internal cells, it can’t fully shrink back into a perfectly smooth shape. That’s what creates those uneven wrinkles and folds.

But then why do some beans still look smooth?

A lot of it comes down to roast level, bean density, and processing method. If you think about the smooth-looking beans you’ve seen, chances are many of them were light roasts. Lightly roasted beans expand less internally, experience shorter pressure buildup, and lose less moisture overall (usually around 12–15% weight loss during roasting). Because the cellular structure remains relatively intact, the surface stays tighter and smoother, with very few wrinkles.

The beans with the most obvious wrinkles are usually medium-dark roasts. These beans expand significantly during roasting, the surface stretches outward, and then they lose a large amount of moisture (typically 15–18% weight loss) while releasing gas. Once cooled, the structure collapses inward, creating those classic walnut-shell-like wrinkles.

Interestingly though, extremely dark roasts can actually appear smoother again. I’m talking about beans roasted well past second crack — the kind that become visibly oily on the surface. At this stage, the bean structure has already been heavily damaged. The surface becomes brittle and porous under extreme heat, often developing a shiny oily coating. The original fine wrinkles get flattened or hidden beneath the oil, creating more of a cracked appearance instead of detailed wrinkles.

But this smoothness is really an illusion created by oils and surface brittleness — very different from the smoothness of a light roast.

Light-roasted beans have a dry, tight surface, almost like a fully stretched drum skin. Their cell structure remains mostly intact, with little to no oil leakage, giving them a matte and delicate smoothness. Deep dark roasts after second crack, on the other hand, develop shiny, reflective surfaces that almost look wax-coated. That oily layer fills in the tiny wrinkles and creates a glossy reflection that makes the beans appear smooth. But if you look closely, you can still spot tiny crack-like patterns — almost like a dried riverbed — rather than the continuous smooth surface seen in light roasts.

Bean density also plays a role. High-altitude hard beans, which are denser, tend to expand more evenly during roasting, so their wrinkles appear more organized and uniform. Lower-altitude softer beans are more likely to develop irregular wrinkles.

Processing methods affect appearance too. Washed coffees usually look cleaner, and their wrinkles appear much more obvious compared to natural-processed coffees.

That’s because washed coffees go through fermentation and water washing after the fruit skin is removed, fully cleaning away the mucilage layer before drying. The resulting green beans have very clean surfaces with only a thin layer of silverskin remaining. Most of that silverskin falls off during roasting, leaving the surface fully exposed. So when the bean collapses and wrinkles form, they appear sharp, direct, and highly visible. Sometimes washed beans almost look like they’ve suddenly “aged” after roasting, haha.

So if you’re trying to guess a coffee’s processing method by appearance, here’s a fun clue: if you see lots of silverskin and very visible wrinkles, there’s a good chance it’s a washed coffee.

Natural-processed coffees are different. In the natural process, the entire coffee cherry — including the skin, fruit, and mucilage — is dried together. During drying, sugars and sticky fruit compounds cling to the parchment layer surrounding the bean, forming a semi-transparent hardened “sugar coating.” During roasting, this layer caramelizes into a brown, crispy shell that still stays attached to the bean surface.

Even if the bean underneath collapses and wrinkles, this caramelized layer softens and masks those sharp edges. Instead of detailed grooves and wrinkles, you see a smoother, more even surface with a slightly textured appearance.

When we drink coffee every day — especially Ethiopian beans, which are often tiny to begin with — washed beans can honestly look pretty “ugly.” Many people assume smooth surfaces and even coloring mean better-looking, higher-quality beans, especially with naturals. But that’s also a kind of disguise. The heavily wrinkled washed beans are actually showing you the bean’s true cellular structure.

Appearance doesn’t equal quality. Sometimes, wrinkles are the most honest face a coffee bean can have, haha.

The Sugar Cane Decaf Process Explained in One Diagram

 As people become more health-conscious, decaffeinated coffee has become a hot topic among coffee enthusiasts. Traditional decaffeination methods usually involve harsh chemicals or sacrifice the coffee's original flavor. For instance, early methods used chemical solvents like methylene chloride to extract caffeine from coffee beans—these chemicals leave behind residual tastes and can pose health concerns. Ever since, decaf coffee has carried a somewhat suspicious reputation.

With technological advancements, the Swiss Water Process became the mainstream decaffeination method. This process uses water filtration to remove caffeine. While considered a safer alternative, it also strips away some desirable flavor compounds from the beans, resulting in coffee that tastes flat or even oddly off-flavor. I'll never forget the time I tasted shiitake mushroom and vegetable bun notes in a Swiss Water decaf—absolutely baffling!

Let's take a quick look at the history of decaffeination. In the early 20th century, German merchant Ludwig Roselius accidentally discovered decaffeination when a batch of coffee beans was soaked in seawater. This prompted him to explore methods for removing caffeine while preserving flavor. Roselius developed the first commercial decaffeination process using the chemical benzene and produced the first instant decaf coffee under the Sanka brand. For decades, chemical decaffeination was the standard practice. However, growing concerns about harsh chemicals and their impact on coffee flavor led producers to explore alternative methods.

In the adult world, we don't want to choose. We want both: the health benefits of low caffeine intake AND the natural flavor quality of coffee itself. Decaffeination methods that follow consumer demand are the ones that gain market recognition. This brings us to the increasingly popular "Sugar Cane Decaf Process."

I believe many of you have heard of this decaffeination method and may have even tried beans processed this way. I've had it a few times while visiting cafés, and my biggest takeaway was : if no one told me it was decaf, I would never have detected any off flavors. The flavor complexity and body were remarkably intact.

So what exactly is the Sugar Cane Decaf Process? And what does sugar cane have to do with it? Let's dive into this topic today.

The name "Sugar Cane Decaf" is primarily a marketing choice—it's easier for consumers to remember and share, and it has a bit of a curiosity-hook appeal. But if we were to name it more scientifically, it should be called the Ethyl Acetate (EA) Decaffeination Process. This method uses a naturally occurring compound called ethyl acetate (EA), which is extracted from fermented sugar cane—hence the "sugar cane" designation.

When talking about the Sugar Cane Decaf Process, we have to mention a Colombian company called Descafecol. They use EA naturally extracted from locally grown sugar cane to decaffeinate coffee. With over 30 years of experience in coffee industrialization, they currently operate two facilities: Colombia's only decaffeination plant and an instant coffee factory. Their clients span 28 countries, so chances are, if you've had coffee processed this way, it likely came from them.

Compared to other decaffeination methods, the sugar cane process retains more of the coffee's original flavor. Here's roughly how it works:

1. Green coffee beans are gently steamed to open their pores and increase permeability

2. The hydrated beans are soaked in an EA solution

3. EA selectively bonds with caffeine molecules and extracts them

4. The beans are separated from the caffeine-rich EA solution

5. The EA evaporates at low temperatures, leaving decaffeinated beans

6. The decaf beans are dried

Natural compounds like EA don't leave chemical residues in the coffee, eliminating health concerns. The entire sugar cane decaf process takes place under low-pressure, low-temperature conditions, minimizing impact on the coffee's delicate flavors. Plus, EA's evaporation temperature is 70°C (158°F), meaning once the beans are roasted, there's no EA residue remaining.

I highly recommend trying sugar cane decaf coffee—even if you're not caffeine-sensitive. The flavor preservation is impressive, offering a delicious and "guilt-free" way to enjoy your cup of joe. It might even shatter any negative stereotypes you've held about decaf coffee.

Panama Geisha Coffee Review 2025｜Carmen Estate Anaerobic Washed Geisha Tasting Notes & Brew Guide

 When “Panama Carmen Estate” comes up, you already know this is another release from Jianjia Specialty Coffee Studio. And sure enough, their new-crop Carmen Estate beans have just come out of the roaster. Back in the 2024 harvest, I was deeply impressed by the magnolia-like elegance of their Mu Yun He Bi Washed Geisha. This new crop, however, brings a noticeably different flavor experience. Today, I want to share this tasting and talk about what’s changed with the new Carmen harvest.

This custom lot from Jianjia Specialty Coffee Studio is entirely processed using a temperature-controlled anaerobic dark-room washed method. Let’s briefly break down how this processing works.

The “dark room” refers to a fully enclosed space where temperature and humidity are strictly controlled—typically low temperature, low humidity—and completely isolated from natural light. During the dark-room drying stage, after the coffee cherries are depulped, the beans are left with their mucilage intact and placed in sealed dark rooms to ferment and dry. This process allows precise control over microbial activity, reduces flavor degradation caused by light oxidation, makes fermentation more predictable, lowers the risk of mold, and preserves a higher level of clean sweetness.

The washing stage may incorporate either anaerobic or aerobic fermentation depending on the specific protocol, resulting in different flavor expressions. After washing removes residual mucilage and impurities, the cup clarity is further enhanced. Coffees processed this way often present a profile that is both clean and intense—combining the bright acidity of washed coffees with the complexity often found in naturals. Tropical fruit notes, floral aromatics, and pronounced sweetness are common, with a clean yet layered mouthfeel.

This custom program from Jianjia includes 16 individual Geisha profiles, released across two batches. To make things even more interesting, they’ve introduced the MBTI 16 personality types as a playful, anthropomorphic way to label each lot—allowing you to “unlock” a batch that matches your personality type.

Each batch includes four different fermentation environments:

• E / I represent honey process vs. washed

• N / S indicate harvest batches (combined with F / T to mark fermentation details)

• F / T denote fermentation styles

• P / J refer to the temperature-control approach used during processing

For example:

• NFP and INFP come from the same fermentation tank but undergo dark-room drying in different post-fermentation states.

• ENFP and ESFP are both honey-processed after fermentation, sharing similar fermentation environments and temperature-control tendencies, though with different data points—ENFP from the first harvest batch, ESFP from the second.

Based on this framework, it’s easy to see that all 16 custom Geisha profiles differ in fermentation type, temperature-control strategy, and directional fermentation design.

The coffee cherries used for the Jianjia × Carmen custom Geisha lots all come from a designated micro-region. The high altitude, dramatic day-night temperature swings, and misty climate give the coffee a distinctive sense of terroir. A directional yeast, dual-temperature fermentation combined with slow dark-room drying and washed processing—custom-designed by Jiuyu—produces a wide range of acids, alcohols, and esters during fermentation. The result is a cup that paints a vivid floral landscape layered on top of its terroir foundation.

Roasting takes place at Ayding Lake, 154 meters below sea level. The negative elevation brings higher atmospheric pressure, a higher boiling point, and denser air, allowing the Ikawa hot-air roasting system to express flavors with exceptional clarity.

Each tube is individually vacuum-sealed, containing 16.5 grams of coffee—just enough extra beans to purge the grinder. That leaves roughly 16 grams per brew. I used an EK43s set to grind size 10, paired with a three-hole Kalita Wave dripper and HIFLUX Korean Lyocell cotton fiber filter paper (fast flow).

The dry aroma after grinding is explosively sweet—almost shockingly so. I immediately picked up notes reminiscent of orange soda, accompanied by white floral aromas similar to magnolia or gardenia. This floral note plays a crucial role: it stands out clearly in the dry fragrance yet feels refined and airy rather than overpowering.

My brew followed a four-pour structure, 60 grams per pour. The first pour included a 25-second bloom. Total brew time was 1 minute 45 seconds, with 240 grams of water poured and 200 grams of final yield—roughly a 1:13 brew ratio.

One defining characteristic of this coffee is its exceptionally high sweetness. This sweetness feels intrinsic to the bean itself—more like the natural sweetness of fresh coffee cherry mucilage once the skin is peeled away, rather than something created during roasting. Think honey-like sweetness, layered with a citrus hard-candy acidity. Within that sweetness, there’s a rounded, tea-like smoothness and depth.

What makes the body particularly special is that it doesn’t feel like a thin, fruit-forward sweetness. Instead, it carries a white tea character, adding structure and elegance. Being able to clearly pinpoint that white tea sensation feels genuinely rare.

In their official cupping notes, the producer describes the flavor as “white fruits,” similar to cherimoya or mangosteen. Personally, I find those fruits quite delicate in flavor, but what they share—and what aligns perfectly with my own experience—is an intense, concentrated sweetness.

This sweetness is not caramelized, nor is it a simple lingering aftertaste. It’s a very concrete, forward-facing sweetness, accompanied by complex floral and fruit aromatics. The sense of refinement comes from how flavor and mouthfeel support each other, leaving you wanting another sip—an experience that feels graceful, lingering, and deeply satisfying.

Gold Washed Coffee Explained: Lemongrass & Ginger Flavor Notes from Colombia Cauca

 In a gold washed coffee, I tasted unmistakable notes of lemongrass and ginger.

A few days ago, I shared a dedicated introduction to what gold washed processing is—a relatively new method that combines the strengths of both washed and natural processing. The first time I encountered a gold washed coffee was last November at the Shanghai Coffee Expo. At the booth of Direct Coffee from Kyoto, this particular coffee immediately caught my eye. That moment marked the beginning of a flavor experience that completely amazed me—one that has stayed with me ever since.

I placed an order for the beans on the spot. This coffee is a Gold Washed Red Bourbon from Popayán, Cauca, Colombia. The barista at the booth was also the roaster of this very coffee, and the way he presented its flavors was incredibly impressive. It was the first time I had ever tasted such distinctly clean and vivid lemongrass and ginger notes in a Colombian coffee built on an innovative twist of traditional processing methods. Ultra-clean, ultra-refreshing, and incredibly smooth. Today, I want to take some time to talk about this coffee in detail. If you ever come across beans from the same region, make sure you give them a try. From what I’ve researched, most of the production from this farm is exported to Japan and Australia.

Popayán is a city in southwestern Colombia, the capital and largest city of Cauca Department. The Cauca region itself is considered one of Colombia’s core coffee-growing areas. Before diving deeper into this coffee, it’s necessary to revisit the concept of gold washed processing and the Santuario Project that I mentioned previously. Santuario is a professional coffee producer and exporter with farms and processing facilities in Colombia, Costa Rica, Brazil, Mexico, Ethiopia, and El Salvador.

The founder of the Santuario Project, Camilo Merizalde, is also behind the Colombian farm where this coffee was produced. His journey into coffee is quite interesting—he originally worked as a financial trader with no background in the coffee industry. During visits to suppliers, he was often asked where to find high-quality Colombian coffee. After returning home to Colombia, he reached out to people working in coffee farming, and that’s how he gradually entered the world of specialty coffee.

“Santuario” means “sanctuary” in Spanish. Camilo envisioned creating a refuge and a dream farm in the Cauca mountains of Colombia. The farm mainly grows Bourbon varieties along with several others, at elevations ranging from 1,850 to 2,100 meters above sea level—nearly ideal conditions for coffee cultivation. The farm also operates a large-scale processing center. Their focus goes beyond simply improving coffee quality; they emphasize developing styles and techniques grounded in scientific processes, ensuring consistent quality year after year.

I also want to briefly talk about Direct Coffee, the roastery based in Kyoto. They don’t have an official brand website, nor is there an abundance of written information about them. However, their official Instagram account has around 11,000 followers, which is quite solid compared to many overseas independent roasters I’ve come across. Judging from this particular coffee, you can get a sense of their roasting philosophy. They use a Diedrich roaster—one of my personal favorite brands.

Diedrich roasters are best known for their infrared heating systems. This technology transfers energy directly through infrared radiation, efficiently delivering heat to the drum and the bean surface while minimizing heat loss to the surrounding air. More importantly, this roasting method helps preserve complexity and sweetness in the coffee. Infrared heat reduces the risk of scorching the bean surface and allows for more even internal and external development. That’s exactly why the coffees they roast have such clean, clearly defined flavor profiles. They place strong emphasis on expressing terroir and highlighting sweetness. When you drink their coffee, you can clearly sense its cleanliness, pronounced sweetness, and a gentle yet gradually bright acidity, with a well-structured and layered overall profile.

As soon as you open the bag, you’re greeted by an intense lemongrass aroma. Honestly, smelling something like this in winter feels like spring blooming inside your heart. Within that strong lemongrass aroma, there’s a hint of ginger lingering in the finish—not the sharp, spicy note of aged ginger, but a fresh, uplifting sweetness reminiscent of young ginger. It’s truly unique. Once ground, these aromas become even more intense and expressive.

I brewed this coffee using two different setups. The first was a V60 Drip-Assist (Smart Dripper) used purely as a V60 cone, just like the barista did at the expo. The valve was kept open throughout, with no immersion involved. The pouring focused on a small central area, mostly using a single continuous pour. I used 92°C water (Nongfu Spring), a brew ratio of about 1:16, and a total brew time of around 1 minute and 55 seconds, including a 20-second bloom. In the V60, the citrus notes really stood out, with acidity that was extremely gentle yet bright. It was a genuinely pleasant sensory experience. The highlight, though, was the mouthfeel—exceptionally smooth and round, almost rolling across the tongue. It felt refined and elegant.

The second method I used was a three-hole flat-bottom dripper paired with Læsseyr filter paper, a setup I’ve been using quite often recently. With this dripper, I usually go for a slightly tighter ratio—around 1:15. Using 15 grams of coffee and yielding about 198 grams of brewed coffee results in an effective ratio closer to 1:13. This slightly higher concentration brings out a richer sweetness, which is exactly what I was aiming for. In the flat-bottom dripper, the flavors came through more boldly: bright lemon and citrus notes, paired with a delicate ginger aroma. The smooth, rounded texture was consistently satisfying in every cup. It’s the kind of coffee that makes you finish it almost without realizing it—pure comfort, like a gentle massage for your taste buds.

Gold Washed Coffee Explained: What Is Gold Washed Processing & Why It Tastes So Sweet

 When shopping for coffee, you may have come across a processing method labeled “Gold Washed.” We’re all familiar with one of the classic processing methods—washed—but what does the addition of gold actually mean? How is it different from traditional washed coffee? Today, I’d like to dedicate this article to exploring exactly what the Gold Washed process is.

I wanted to write this piece because I recently encountered an outstanding roaster from Kyoto at a coffee festival. They were showcasing a Red Bourbon from the Popayán region of Cauca, Colombia, processed using the Gold Washed method. That coffee left a deep impression on me—it was simply too good. Naturally, it sparked my curiosity to dig deeper into this processing style. (I’ll be sharing a full tasting review of that coffee later. I couldn’t resist and ordered two bags on the spot—no hesitation at all.)

When it comes to “Gold Washed,” there is a certain degree of producer-specific ownership to the method. By that, I mean that while the process can be learned and replicated, most of the Gold Washed coffees currently available on the market come from Santuario Project. Santuario is a professional coffee producer and exporter with farms and processing facilities in Colombia, Costa Rica, Brazil, Mexico, Ethiopia, and El Salvador.

In this article, we’ll focus on two things:

1. The overall workflow of the Gold Washed process

2. The specific advantages it brings to flavor expression

In simple terms, Gold Washed combines the strengths of both washed and natural processing. It does not strictly belong to the traditional washed category. Instead, it can be seen as a more refined, upgraded version of washed processing. The core goal is to retain the clean, bright flavor profile of washed coffees while introducing the enhanced sweetness, fruit complexity, and body commonly found in natural processing—through carefully controlled fermentation.

To better understand this, let’s compare it step by step with the traditional washed process.

The initial steps are exactly the same. First comes harvesting and flotation: only fully ripe red cherries are picked, then placed in water tanks to remove floaters, defects, and debris. Next, a depulping machine removes the outer skin and most of the fruit flesh. At this stage, the coffee beans are still coated in a sticky layer of mucilage.

Up to this point, the process is identical to traditional washed coffee. The key difference begins during the mucilage fermentation stage. In a classic washed process, mucilage-covered beans are submerged in water for underwater fermentation, typically lasting 12–36 hours. After fermentation, the mucilage is completely washed away with large amounts of clean water, followed by drying.

Gold Washed processing takes a different approach. Instead of fermenting underwater, the beans—still coated with mucilage—are placed in a dry or semi-dry environment (without full water immersion) for a longer, tightly controlled dry fermentation, which may last several days. During this time, temperature, pH levels, and humidity are closely monitored.

The reason for this method is to allow microorganisms—such as yeasts and bacteria—to interact more deeply with the mucilage, producing more complex sugars and flavor compounds. At the same time, the beans are not in contact with the full fruit mass as in natural processing, making the process more controllable and consistent in quality. This is a critical distinction: traditional washed processing prioritizes efficiency and cleanliness, often washing away much of the fermentation-driven flavor potential. Gold Washed coffees, on the other hand, manage to preserve the cleanliness of washed coffees while capturing the sweetness and expressive character typically associated with naturals.

Next comes the drying stage. In traditional washed processing, fully washed parchment coffee (still wrapped in its inner skin) is dried on patios or in mechanical dryers until moisture content reaches around 11–12%. With Gold Washed, after fermentation reaches its intended endpoint, the beans may be lightly rinsed with water, but not thoroughly washed as in traditional methods, before moving on to drying. (Perhaps this brief contact with water is why it still carries the “washed” name—just a thought.)

This gentle rinse is more important than it might sound. Its purpose is to halt fermentation, preventing over-fermentation and ensuring flavor balance in the final cup.

Because of the extended and carefully managed fermentation, Gold Washed coffees tend to develop higher sugar content, resulting in a pronounced sweetness. At the same time, they retain the hallmark bright acidity of washed coffees—often reminiscent of citrus, lemon, or green apple. The overall flavor profile is clean and well-defined, yet layered with notes of stone fruits (such as peach or apricot), berries, and sometimes even subtle tropical fruit nuances. The mouthfeel is rounder and smoother. (Honestly, I found almost all of these characteristics in the coffee I tasted—and it was incredibly satisfying.)

I really enjoy sharing these less common but thoughtfully designed processing innovations—methods that push boundaries without resorting to extreme or gimmicky techniques. Gold Washed is a great example of a modern processing approach that uses precise fermentation control to optimize flavor. It doesn’t aim to overthrow tradition, but rather to refine it.

If you appreciate the cleanliness of washed coffee but wish for more sweetness and fruit complexity, then the next time you see a coffee labeled Gold Washed, don’t hesitate. It’s absolutely worth trying.

Co-Fermentation vs Yeast Fermentation: What’s the Real Difference in Specialty Coffee?

 In recent years, “flavor-enhancing” coffee processing methods have become one of the most talked-about topics in the industry. As more and more unconventional techniques emerge, it’s easy for concepts to get blurred and definitions to overlap. Clarifying these processing methods can be genuinely helpful when you’re choosing coffee beans in the future—it gives you a more concrete framework and makes it easier to identify the flavor profiles you actually enjoy.

One of the most commonly confused pairs is co-fermentation and yeast fermentation. Some marketing narratives even lump yeast fermentation directly into the category of co-fermentation. In reality, the two should be seen as parallel but distinct approaches. Today, let’s take a closer look at how they differ.

Co-fermentation and yeast fermentation are essentially two major branches within flavor-enhancing coffee processing, covering the vast majority of “boosted flavor” coffees you’ll find on the market. They do share certain similarities. At their core, both aim to amplify the flavor potential already present in the coffee cherry, allowing producers to guide flavor direction and sensory characteristics—and, as a result, often increase the coffee’s economic value.

Put simply, co-fermentation involves adding external organic substrates—such as fresh fruit pulp or fruit juice—during the fermentation process. Yeast fermentation, on the other hand, deliberately introduces specific yeast strains into fermentation to create distinctive flavor profiles.

Because of this, you’ll notice that both methods rely on external organic materials and compounds to produce flavors that terroir alone might not create. Yet there is a fundamental difference between them. A key point lies in co-fermentation methods that add ingredients like passion fruit, orange juice, or lemon juice. These additions don’t actually aid fermentation itself; the coffee beans mainly absorb the flavors of the added fruit. This is why many people view co-fermentation as a form of “flavor cheating.”

Yeast fermentation works differently. Here, specific microorganisms participate throughout the entire fermentation process, still following—and actively engaging in—the essential stages of traditional coffee fermentation. The introduction of targeted yeast strains leads to the formation of new sugars and compounds that generate unique flavors. In this sense, yeast fermentation is closer to a “natural selection” process, involving far less direct human intervention compared to co-fermentation.

At its core, yeast fermentation draws heavily from techniques used in craft beer brewing. Specific yeast strains may be introduced before or during fermentation. A yeast strain is a particular variant within a yeast species, defined by unique genetic traits that influence how it metabolizes sugars and, ultimately, the flavors it produces.

Much like in craft beer or winemaking, this process can be controlled in multiple ways to create a wide range of flavor outcomes. Fermentation is essentially the microbial breakdown of sugars. Even without adding selected strains, fermentation is already a natural part of traditional coffee processing—processing methods, at their heart, are all about managing fermentation well. And even with specific yeasts introduced, the final flavor always retains a degree of unpredictability. It’s precisely this uncertainty that further distinguishes yeast fermentation from co-fermentation.

Co-fermentation, by contrast, introduces new microorganisms and new sugar sources through the addition of fruit juices or pulps. These fruits naturally carry their own microbial populations, which further alter and complicate the fermentation process. At the same time, this approach makes flavor outcomes far more predictable. Most fruits already have strong, recognizable aromas and flavors, and coffee beans inevitably absorb them during fermentation. As a result, you’ll often find very clear, unmistakable fruit notes in both dry and wet aroma.

From my own brewing experience, a lemon co-fermented coffee is a perfect example. No matter how you brew it—even brewing blindly—you’ll almost certainly end up with a pronounced lemon juice flavor. In fact, even after the coffee is gone, the container that held the beans can still retain a lingering lemon aroma.

Both co-fermentation and yeast fermentation currently fall within what the market broadly accepts as legitimate “flavor-enhancing” processing methods. They are fundamentally different from so-called “flavored coffees” made with artificial additives. As consumer awareness grows and supply chains become more transparent, these processes are now far more traceable than in their early days. Green coffee traders and roasters alike typically provide clear documentation of the entire processing method and strive to name these processes in more straightforward, honest terms.

That said, for consumers, these definitions can still feel complex and abstract. A clearer conceptual understanding is essential—not just to know what kind of coffee you’re actually drinking, but to decide whether it’s truly the kind of coffee you want in your cup.

A Rare Cold-Washed Obata Coffee from Denmark’s POMA Lab

 A few days ago, I introduced the cold-wash processing method developed by POMA Lab in Denmark, and I mentioned that I’d soon share a flavor review of the beans they grow and roast themselves. This is actually the first time I’ve ever tasted coffee beans produced directly from a research lab. Since they are both the growers and the roasters, this batch definitely counts as a rare find—haha.

POMA is a coffee research and roasting company founded in Copenhagen in 2024. Their mission is to develop coffee production technologies that can be easily adopted by farmers around the world, helping address industry challenges and bridge the gap between research and real-world application. Their main research facility is a greenhouse on the Danish island of Funen, where they simulate different farm microclimates to observe, study, and adjust various coffee production methods.

They developed the POMA Cultivation System—a comprehensive set of best agricultural practices designed to unlock the full potential of both new and existing varieties while pushing coffee production toward greater systematization and standardization. The system combines cutting-edge scientific research with practical field-tested methods, making it not only innovative but also highly accessible to farmers.

Inside the greenhouse, they manipulate environmental factors using plant-growth simulation algorithms. This allows them to study how coffee trees respond to climate change while maintaining stable conditions to examine the effects of farming practices. Their experiments cover nearly every aspect of coffee cultivation, with a special focus on crop-load management, growth regulation, water and nutrient optimization, and understanding how climate affects coffee quality and plant physiology.

Currently, they’re studying widely cultivated varieties such as Bourbon, Typica, Pacamara, Catuai, Caturra, and Geisha, ensuring their work remains directly relevant to farmers. All research findings are openly available for validation in real-world production environments. Typically, it takes 8 to 12 years for a technique to go from initial lab work to becoming a tool farmers can reliably use. In a way, that timeline reflects a kind of dedicated, almost spiritual commitment.

So POMA isn’t just “doing experiments in a lab.” They also collaborate closely with farms, transferring their technology to real-world applications and helping solve practical production challenges to make sustainable practices more accessible and effective. Their current projects include soil nutrition, shading systems, crop-load management, controlled pollination, and microclimate studies.

The beans I purchased this time come directly from the POMA Research Station, grown in an environment engineered to simulate an altitude of around 1,000 meters. The variety itself is quite special—and it’s my first time trying it. It’s called Obata, a modern Arabica hybrid created by the Campinas Agronomic Institute (IAC) in Brazil. The variety is a cross between Timor Hybrid (which contains Robusta genes) and Villa Sarchi, giving it both disease resistance and specialty-coffee potential.

A bit about the parent varieties:
Timor Hybrid—often called “Tim Tim”—is itself a cross between Arabica and Robusta. The beans are huge and elongated, sometimes even nicknamed “Long Mandheling.” Thanks to its Robusta lineage, Tim Tim typically has low to medium acidity, a heavy body, and strong viscosity.
Villa Sarchi, on the other hand, is a natural Bourbon mutation from Costa Rica, known for its lively acidity and sweetness. So you can imagine: one parent leans deep and balanced, the other bright and sweet—a complementary pairing, haha.

The core of the cold-wash process is an initial 48-hour chill at 8°C. After that, the cherries are fully depulped and washed, then dried in a pressurized rotating dryer at temperatures below 10°C. This low-temperature environment forces yeast and the beans themselves into a dormant state, inhibiting fermentation. The goal is to preserve and amplify the coffee’s inherent aromas without introducing additional yeast or triggering active fermentation. Essentially, the process aims to showcase the purest, most natural expression of the coffee beans.

They even performed pre-roast GC-MS analysis on cold-washed green coffee. Using Caturra as an example, they found that key aromatic compounds were better preserved and enhanced compared to traditional washed processing.

Each batch from POMA comes in a paper box, and inside is a vacuum-sealed one-way-valve bag. Before opening, it feels hard like a brick—haha. Once opened, the beans don’t give off any particularly strong aroma, but you can immediately notice their size—likely thanks to the Tim Tim lineage. After grinding, the dry fragrance shows hints of cooked apple and a light touch of spice, but overall, the aroma is relatively subtle without any unpleasant notes.

I treated this coffee both as a daily drinker and a test subject for more controlled brewing parameters. Across several brews, its main characteristics became clear: the sweetness is strong and consistent throughout. Even though the flavor profile at higher temperatures feels somewhat muted, the sweetness remains steady. As the temperature drops, the acidity rises and becomes pleasantly citrus-like, with some sweetness reminiscent of red berries. However, if you brew it with a fast-drip method, it may reveal the same weakness as its dry aroma—its flavor structure is relatively short. There aren’t many layers to latch onto; its main strengths are sweetness, cleanliness, and a light, balanced cup profile.

Compared to traditional washed coffees, I find this one more approachable and much more forgiving across brewing methods. You’ll almost never get overly bright acidity—haha. Its sweetness and balance make it appealing to a wider range of drinkers.

As for the bean variety itself, neither Timor Hybrid nor Villa Sarchi is considered a “premium” or prestigious cultivar. Both have flavor limitations. The typical “wild” character of Timor is barely noticeable in this hybrid. Its balance and cleanliness make it feel more restrained, though at the cost of losing some of the distinctive traits associated with its lineage. Ultimately, it comes down to personal preference. If you’re seeking smooth mouthfeel and an easy-drinking profile, Obata is absolutely worth trying. But if you’re looking for layered complexity and strong flavor identity, it may leave you disappointed.