Unlocking Flavor: Navigating Grind Size for Washed vs. Natural Coffees

Question: How should home brewers adjust grind size when switching between washed and natural coffees?

Unlocking Flavor: Navigating Grind Size for Washed vs. Natural Coffees

For the home brewer, the quest for the perfect cup often involves a delicate dance of variables. Water temperature, brew time, and water-to-coffee ratio are familiar partners in this dance. Yet, one of the most impactful, and sometimes overlooked, elements is the size of your coffee grounds. When venturing between washed and natural coffees, a simple adjustment to your grinder can unlock a world of nuanced flavors. While the underlying physics of extraction are complex, understanding the fundamental differences between these processing methods can guide your grind size decisions.

The Processing Divide: How Nature and Water Shape the Bean

The primary distinction between washed and natural coffees lies in how their fruit, the cherry, is handled after harvesting. Washed coffees undergo a pulping process, where the outer layers of the cherry are removed before fermentation in water. This fermentation stage is crucial for breaking down the mucilage, the sticky layer beneath the skin. The acidity of washed Ethiopian coffees, for instance, is typically reported to be in the range of 4.5 to 5.5 [Context excerpt 1]. This method generally results in cleaner, brighter cups, emphasizing the inherent characteristics of the bean itself.

Natural, or dry-processed, coffees, on the other hand, are dried whole with the fruit intact. This means the beans absorb sugars and compounds from the surrounding cherry pulp as they dry. This extended contact with the fruit can impart distinct fruity, boozy, or even wine-like notes to the final coffee. The sugars from the mucilage are believed to contribute significantly to these flavors, and the presence of these components influences the extraction process differently than in washed coffees.

The Grindstone of Extraction: Matching Size to Process

So, how does this processing difference translate to your grinder? Research on extraction kinetics, particularly in espresso, has shown that particle size significantly influences the extraction of various compounds [1]. While these studies often focus on espresso, the principles can inform other brewing methods. Smaller particles offer a larger surface area for water to interact with, leading to faster extraction. Conversely, larger particles have less surface area, resulting in slower extraction.

When brewing natural processed coffees, the goal is often to tame some of the intense fruitiness and boozy notes that can arise from the sugars present in the mucilage. These sugars can extract quite readily. Therefore, a slightly coarser grind compared to your usual setting for washed coffees can be beneficial. This coarser grind slows down the extraction rate, preventing the over-extraction of these sugary compounds, which can lead to a muddled or overly sweet cup. It allows for a more balanced presentation of the coffee’s complexity, letting the nuanced flavors emerge without being overwhelmed.

Conversely, washed coffees, with their inherent brightness and cleaner profiles, often benefit from a grind that allows for more complete extraction of their delicate aromatics and acidity. Because they generally lack the high concentration of readily extractable sugars found in naturals, you can often get away with a slightly finer grind. This increased surface area facilitates a more thorough extraction of the coffee’s intrinsic flavors, bringing out its vibrant acidity and aromatic complexity. However, it’s a fine line; grinding too fine can still lead to over-extraction and bitterness, so careful observation of your brew is key.

It’s important to note that while differences in grind profiles between coffees of different origins and processing methods have been observed, these differences can sometimes be minor [2]. This underscores that while processing is a significant factor, other variables such as bean density, roast level, and even the temperature at which the coffee is ground can influence particle size distribution [2]. Therefore, these are guidelines, not rigid rules. The best approach is always to start with a small adjustment and taste.

Fine-Tuning Your Brew: The Art of the Adjustment

When making the switch, begin by adjusting your grinder one or two notches coarser for natural coffees if you’re accustomed to a specific setting for washed coffees. For washed coffees, try moving one or two notches finer. Pay close attention to the taste. If your natural coffee still tastes too sweet or boozy, try grinding even coarser. If your washed coffee tastes a bit muted or underdeveloped, a slightly finer grind might be in order. Observe your brew time as well; a change in grind size will inevitably affect how quickly water flows through your coffee bed.

In conclusion, understanding the impact of coffee processing on bean chemistry and extraction dynamics can empower home brewers to achieve better results. By adopting a slightly coarser grind for natural coffees to moderate sugar extraction and a slightly finer grind for washed coffees to enhance aromatic and acidic expression, you can unlock the full spectrum of flavors each processing method has to offer. This thoughtful adjustment to your grind size is a powerful yet accessible tool in your pursuit of the perfect cup.

References

[1] — Benedikt K L Schmieder, Verena B Pannusch, Lara Vannieuwenhuyse, Heiko Briesen, Mirjana Minceva — Influence of Flow Rate, Particle Size, and Temperature on Espresso Extraction Kinetics. — 2023-Jul-28 — https://pubmed.ncbi.nlm.nih.gov/37569140/ [2] — Erol Uman, Maxwell Colonna-Dashwood, Lesley Colonna-Dashwood, Matthew Perger, Christian Klatt, Stephen Leighton, Brian Miller, Keith T Butler, Brent C Melot, Rory W Speirs, Christopher H Hendon — The effect of bean origin and temperature on grinding roasted coffee. — 2016-Apr-18 — https://pubmed.ncbi.nlm.nih.gov/27086837/