Beyond the Brew: Decoding Coffee Bean Processing Through Visual Cues

Question: When selecting beans, how can I tell if a coffee was “washed” versus “natural” processed just by looking at the beans themselves?

As coffee enthusiasts, we often delve into the nuances of origin, varietal, and roast. Yet, the journey from cherry to bean—specifically, the post-harvest processing method—profoundly shapes the final cup. Two prevalent methods are ‘washed’ and ’natural.’ While the impact on flavor is significant, can we discern these differences by simply looking at the green beans themselves? The answer, unfortunately, is not definitively.

The Visual Challenge

When examining raw, unroasted coffee beans, subtle visual cues that reliably distinguish between washed and natural processing are scarce. The primary differences in these methods occur during the removal of the coffee cherry’s outer layers and the subsequent drying stages. Washed processing involves depulping the coffee cherries, fermenting them to remove the mucilage (a sticky layer), and then washing the beans thoroughly [3]. Natural processing, conversely, involves pulping the cherries and then drying them with the fruit pulp intact, allowing the bean to absorb sugars and flavors from the fruit during this extended period [2].

Inferring from Processing Principles

Although direct visual identification is difficult, an understanding of the processes can offer indirect clues, particularly when considering the potential for residual matter. In the natural process, where the entire cherry is dried around the bean, there’s a theoretical possibility for more organic residue to cling to the bean’s surface compared to a thoroughly washed bean. However, diligent processing in both methods aims for a clean bean ready for roasting. Researchers have noted that the ‘washed process involves depulping the coffee cherries, fermenting them to remove the mucilage, and then washing the beans’ [3]. This meticulous washing step is designed to leave a clean surface. Therefore, while one might hope for a visual indicator of more ’natural’ adherence to the bean, it’s not a reliable marker. The key distinctions lie not in the outward appearance of the green bean but in its internal chemical composition and the resultant flavor profile.

Flavor Signatures as Proxies

Instead of visual cues, the most significant indicators of washed versus natural processing are found in the cup. Washed coffees are often characterized by a cleaner, brighter acidity and more pronounced origin-specific flavors, sometimes described with notes of citrus or floral qualities [4, 5, 6]. This is because the removal of the mucilage layer before drying allows the inherent flavors of the bean to express themselves without the influence of fermenting fruit sugars. In contrast, natural processed coffees frequently exhibit more complex, fruity, and sometimes wine-like characteristics. The prolonged contact with the fruit pulp during drying can imbue the bean with deeper, richer flavors, potentially contributing notes of berries or tropical fruits [2].

Conclusion

While the fascination with deciphering coffee beans through sight alone is understandable, the visual differentiation between washed and natural processed beans is not a straightforward or reliable method. The true story of these processing techniques is revealed not in the appearance of the green bean but in the intricate interplay of chemical compounds that ultimately contribute to the diverse and captivating flavors we experience in our brewed coffee. For those seeking to understand their coffee’s journey, focusing on the origin, varietal, and processing method stated by the roaster will offer far greater insight than a visual inspection of the beans themselves.

References

[1] — Magdalena Zdanowicz, Marta Rokosa, Magdalena Pieczykolan, Adrian Krzysztof Antosik, Katarzyna Skórczewska — Biocomposites Based on Wheat Flour with Urea-Based Eutectic Plasticizer and Spent Coffee Grounds: Preparation, Physicochemical Characterization, and Study of Their Influence on Plant Growth. — 2024-Mar-06 — https://pubmed.ncbi.nlm.nih.gov/38473683/ [2] — Rongsuo Hu, Fei Xu, Liyan Zhao, Wenjiang Dong, Xingyuan Xiao, Xiao Chen — Comparative Evaluation of Flavor and Sensory Quality of Coffee Pulp Wines. — 2024-Jun-27 — https://pubmed.ncbi.nlm.nih.gov/38999011/ [3] — Magdalena Zarebska, Natalia Stanek, Krzysztof Barabosz, Anna Jaszkiewicz, Renata Kulesza, Rafał Matejuk, Dariusz Andrzejewski, Łukasz Biłos, Artur Porada — Comparison of chemical compounds and their influence on the taste of coffee depending on green beans storage conditions. — 2022-Feb-17 — https://pubmed.ncbi.nlm.nih.gov/35177718/ [4] — Michał Halagarda, Paweł Obrok — Influence of Post-Harvest Processing on Functional Properties of Coffee ( — 2023-Nov-01 — https://pubmed.ncbi.nlm.nih.gov/37959805/