What Affects Coffee Cleanliness? What Are the COE Cupping Evaluation Items? Why is Brazil the World's Largest Coffee Producer?

The Importance of Coffee Cleanliness

"Cleanliness" is the first scoring item in COE cupping. If coffee fails to achieve a passing score in initial cleanliness during cupping, subsequent items will also fail. This demonstrates how crucial cleanliness is for a cup of coffee!

What is Coffee Cleanliness?

In the world of coffee, cleanliness refers to the absence of any negative flavors or sensations that affect the tasting experience. Earthy notes, hay, and woody flavors are common representatives of negative flavors, while astringency and roughness are examples of negative sensations.

Causes of Coffee "Uncleanliness"

There are many reasons why coffee might be "unclean." Coffee harvesting, processing, roasting, and brewing are all important factors that affect cleanliness. Let's first discuss harvesting and processing, as COE's emphasis on cleanliness largely stems from the harvesting and processing methods of Brazilian coffee at the time.

As we know, Brazil is the world's largest coffee-producing country! Its coffee production accounts for one-third of global production, yielding over thirty million bags (60kg/bag) annually. Therefore, such enormous quantities naturally cannot be hand-harvested as fully ripe cherries (this concept didn't exist back then). Coincidentally, most of Brazil's coffee plantations are flat, so Brazil invested in mechanical harvesting. Unlike humans, machines cannot identify fruit maturity, so in this situation, both ripe and underdeveloped cherries are all harvested together by machines.

(Although, wouldn't this method of screening beans hit people in the face?) Most of us have probably eaten unripe fruit before! The obvious and prominent astringent feeling, with a bland taste, applies equally to coffee. However, for Brazil at the time, coffee was already an ordinary agricultural crop that didn't require special treatment. So there was no sorting after harvesting—instead, everything was directly piled into processing plants for simple sun-drying before being exported for sale. How simple was it? Simply spread on the ground, and coffee cherries began their drying process. Before the concept of specialty coffee emerged, most coffee-producing countries would use crude sun-drying methods to process coffee cherries. This crude sun-drying method causes coffee cherries to absorb a lot of dust, developing negative flavors like earthiness and hay. (For more information on the crude sun-drying process, you can refer to previous articles~)

Even post-processing storage didn't provide proper storage for coffee beans. Large amounts of mold and insect damage were common occurrences, all of which would add undesirable negative flavors to coffee. Therefore, at that time, coffee could only rely on the bitterness developed through deep roasting to mask these negative flavors. But as roasting techniques continued to improve, the mainstream shifted from dark to light roasts, gradually exposing these shortcomings. So various countries began to re-examine the upstream coffee industry, improving harvesting and processing, ultimately enhancing bean quality. Although bean quality improved, some defective beans were still mixed in, which is unavoidable. Therefore, before roasting, we first sort out defective beans from the coffee, then proceed with roasting. Next, let's discuss how roasting and brewing affect coffee cleanliness~

How Roasting Affects Coffee Cleanliness

During the coffee bean roasting process, beans produce a large amount of water vapor due to moisture evaporation within the beans, while the expansion of bean volume causes the silver skin to separate. At this point, we need to increase the airflow to expel steam and silver skin. If not adjusted in time, the thin, cicada-wing-like silver skin will quickly burn under high temperatures, then transform into tiny carbon particles that adhere to the coffee beans. We can understand this as charcoal attaching to food, adding burnt and smoky flavors to the coffee.

In addition, under-roasting leading to underdevelopment can also cause coffee to develop negative flavors like greenness and hay; as well as freshly roasted coffee, due to excessive internal gases, which not only hinders hot water extraction but also causes coffee to have a rough sensation—a negative feeling where coffee feels scratchy in the throat after drinking. These can all be considered miscellaneous flavors imparted by roasting, factors that reduce coffee cleanliness.

How Brewing Affects Coffee Cleanliness

This is easier to understand—under-extraction and over-extraction! Besides desirable flavor compounds, coffee also contains some negative, undesirable flavors. These flavors are generally released continuously during extraction, but because their release efficiency is lower, they are masked by positive flavors when extraction is appropriate. However, once under-extraction occurs, they become prominent: sharp acidity, greenness, and hay are all negative sensations/flavors that affect overall cleanliness when coffee is under-extracted.

And when we over-extract, these inconspicuous miscellaneous flavors continue to accumulate. When they exceed a certain quantity, they will no longer be masked by positive flavors, ultimately filling the entire cup with unpleasant negative flavors like woody and smoky notes, thus reducing cleanliness. Therefore, we can understand that coffee cleanliness is affected by every aspect of the coffee industry. The cleaner a cup of coffee is, the higher its quality, the more appropriate its roast, and the more proper its extraction during brewing.

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