Decoding the Bean's Journey: Brewing Clues to Coffee Processing Methods

Question: What everyday observations during the brewing process (like bloom or extraction rate) might hint at the coffee’s processing method without knowing it beforehand?

The Eloquent Bloom: A Sign of Fermentation

The initial ‘bloom’—the bubbling and expansion that occurs when hot water first meets coffee grounds—can be a telling sign. This release of carbon dioxide (CO₂) is a natural byproduct of coffee bean respiration and, importantly, fermentation [3]. While all roasted coffee will degas to some extent, coffees that have undergone specific fermentation protocols, particularly longer or more active ones, might exhibit a more vigorous or prolonged bloom. For instance, research has shown that aerobic and anaerobic fermentation treatments can positively influence volatile compound concentrations [3]. A more pronounced bloom, therefore, could indirectly suggest a processing history involving more intensive fermentation stages, hinting at methods like extended natural or experimental fermentation processes, rather than a rapid wash.

Extraction Rate and Crema: Echoes of Bean Structure and Lipids

The speed at which water extracts soluble compounds from the coffee grounds, often referred to as the extraction rate, can also offer clues. While influenced by grind size and water temperature [7], the inherent structure of the bean, which is affected by processing, plays a role. For example, washed coffees, with their mucilage removed, tend to have a cleaner, more predictable extraction. In contrast, natural processed coffees, where the fruit remains intact during drying, might present a slightly different extraction profile due to the presence of sugars and other compounds from the pulp. Furthermore, the quality and stability of the espresso crema can be indicative. Crema, the reddish-brown foam atop an espresso, is formed by CO₂ and emulsified oils [1]. The lipid content and the way these lipids interact with proteins in the coffee can influence foamability. While not directly tied to processing method in isolation, the presence of certain bean varietals or the removal of specific bean components during processing might subtly affect the lipid profile, thus impacting crema stability and appearance [1].

Volatile Compounds and Acidity: The Inner Workings

While not always directly observable without analytical tools, the underlying chemical changes wrought by processing can manifest in subtle ways during brewing. Research on fermentation treatments has highlighted their positive influence on pH and acidity, as well as volatile compound concentrations [3]. A coffee that brews with a particularly bright, zesty acidity might, in some instances, be a product of a processing method that preserved or enhanced these characteristics, such as controlled fermentation that managed pH levels effectively. Conversely, coffees processed with less intervention, like certain natural or honey processes, might present a different spectrum of volatile compounds, leading to a more fruit-forward or fermented flavor profile that, while perceived in taste, begins its journey from the bean’s processing.

Beyond the Obvious: A Holistic View

Ultimately, these observations—the bloom’s vigor, the extraction’s pace, the crema’s character, and even perceived acidity—are pieces of a larger puzzle. They are not definitive diagnostic tools but rather subtle hints. A truly skilled brewer, attuned to these nuances, can begin to infer aspects of a coffee’s journey from cherry to cup. For instance, a lively bloom followed by a swift extraction and a rich crema might point towards a carefully fermented natural process, while a less exuberant bloom and a slower extraction could suggest a washed coffee. As understanding of coffee processing deepens, so too does the ability to ‘read’ these subtle cues, enriching the appreciation of each brewed cup.

References

[1] — Ernesto Illy, Luciano Navarini — Neglected Food Bubbles: The Espresso Coffee Foam. — 2011-Sep — https://pubmed.ncbi.nlm.nih.gov/21892345/ [2] — 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/ [3] — Gustavo Galarza, Jorge G Figueroa — Volatile Compound Characterization of Coffee ( — 2022-Mar-21 — https://pubmed.ncbi.nlm.nih.gov/35335365/ [4] — Katarína Poláková, Alica Bobková, Alžbeta Demianová, Marek Bobko, Judita Lidiková, Lukáš Jurčaga, Ľubomír Belej, Andrea Mesárošová, Melina Korčok, Tomáš Tóth — Quality Attributes and Sensory Acceptance of Different Botanical Coffee Co-Products. — 2023-Jul-11 — https://pubmed.ncbi.nlm.nih.gov/37509767/ [5] — Rongsuo Hu, Fei Xu, Xiao Chen, Qinrui Kuang, Xingyuan Xiao, Wenjiang Dong — The Growing Altitude Influences the Flavor Precursors, Sensory Characteristics and Cupping Quality of the Pu’er Coffee Bean. — 2024-Nov-28 — https://pubmed.ncbi.nlm.nih.gov/39682914/ [6] — 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/ [7] — 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/ [8] — Mackenzie E Batali, William D Ristenpart, Jean-Xavier Guinard — Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee. — 2020-Oct-05 — https://pubmed.ncbi.nlm.nih.gov/33020560/