There are many reasons why we might fall in love with a cup of coffee. It could be its rare and complex flavor profile, a rich and weighty mouthfeel, layered and evolving notes, or even the story behind where it comes from. Beyond these, there are also some more niche reasons. For example, I have quite a few friends who judge a coffee by one key word: “clean.”
Here, “clean” doesn’t mean visual clarity, nor does it mean a coffee with low flavor complexity or “nothing going on.” Instead, it refers to a cup that is free of any unpleasant off-flavors, with flavors that are well-defined and easy to distinguish. It may sound simple, but achieving this level of cleanliness actually places very high demands on coffee quality. From growing and processing to roasting and brewing—in short, every step from seed to cup needs to be handled with great care.
Before the concept of specialty coffee became widespread, exported green coffee was often processed in rough, unsophisticated ways by local farmers. As a result, it was common for coffee to carry undesirable flavor defects. In the old version of the SCAA flavor wheel, there was even a dedicated section known as the “negative flavor wheel.”
So what is the negative flavor wheel? It refers to flavors that are universally recognized as unpleasant—defective notes that make coffee uncomfortable to drink. As mentioned earlier, these defects can arise at many stages along the coffee chain. For example, when unripe beans are mixed in, the brewed coffee may exhibit grassy or hay-like flavors, usually caused by harvesting underripe cherries. Poor control during processing can lead to mold or over-fermentation, resulting in musty or moldy notes. Uneven roasting can cause scorching, producing smoky flavors, while underdeveloped roasts may bring out dry, hay-like characteristics.
Beyond outright defects, extraneous flavors also play a role in perceived cleanliness. These are flavors that detract from clarity. They include defects, but are not limited to them. For instance, imagine tasting a coffee whose main profile should be berries and citrus, but you also find notes of nuts, cocoa, or toasted bread mixed in. While these aren’t necessarily negative flavors on their own, when they appear in a fruit-forward coffee, they can make the cup feel cluttered and unfocused—like a room filled with good furniture, but arranged in complete chaos. This, too, is a sign of insufficient cleanliness.
With the arrival of the specialty coffee era, people at every stage of the supply chain have begun to prioritize quality. Fully ripe cherry harvesting has become standard practice in most producing regions, and processing techniques have grown increasingly refined. As a result, many undesirable flavors are eliminated right at the source. For us as end consumers, choosing a reliable roaster (for example… me—I’m very reliable) means that our attention can largely shift to the final step: brewing. With green buyers and roasters acting as multiple layers of quality control, it’s unlikely that truly poor-quality beans will end up in our hands.
In addition, factors such as dirty brewing equipment with residual oils, filter papers with strong papery flavors, or coffee that is too fresh and carries a “green” or restless sharpness can all introduce unwanted notes and reduce clarity. So it’s not just about extraction parameters—every small detail during brewing needs to be carefully controlled. Only then can we brew a truly clean cup of coffee.
Generally speaking, if you start with high-quality beans and use reasonable extraction parameters, your coffee will almost always display excellent clarity. If you’d like to experience a particularly clean cup, I recommend trying two coffees from my lineup: Esmeralda Estate · Washed Green Label Geisha and Ethiopia · Natural ALO. Brew them with a water temperature of 92°C (198°F), a brew ratio of 1:16, an extraction time of 2:00–2:20, and a grind size where 75–80% passes through a #20 sieve.
With these parameters, you’ll get a beautifully clean cup. The former offers clearly defined notes of citrus, jasmine, and green tea, while the latter expresses mango, pineapple, and magnolia. Both are driven by bright acidity and gentle sweetness, with a silky, cream-like mouthfeel and a clear, uplifting sense of clarity.
