Beyond the Bean: Processing Methods for a Mellower Coffee Cup

Question: If I want a coffee that’s naturally lower in acidity, which processing methods tend to result in a mellower cup?

The Alchemy of Acidity in Coffee

The quest for a coffee that is naturally lower in acidity often leads us to consider the bean itself, its varietal, and how it’s roasted. However, a crucial, yet sometimes overlooked, factor shaping a coffee’s perceived acidity is its post-harvest processing. The journey from cherry to roasted bean involves a series of transformations, with fermentation playing a pivotal role in developing the complex array of flavors and aromas we enjoy, and crucially, influencing the titratable acidity in the final cup [2, 5].

Fermentation’s Fingerprint: Washed vs. Natural Processes

Coffee processing methods can be broadly categorized, with the ‘washed’ and ’natural’ (or dry) processes being two of the most prominent. Each method offers a distinct pathway for the coffee cherry to dry and develop its characteristic flavor profile.

The Washed Process: A Cleaner Slate

The washed process involves removing the coffee cherry’s pulp and mucilage before the beans are dried. This method, sometimes referred to as the ‘wet’ process, is known for producing a cup with a cleaner, brighter taste. While this often translates to vibrant notes, it can also highlight acidity, particularly fruity and citrusy characteristics [5, 6, 7]. Research indicates that this method, by removing the fruit layers early, can lead to a cup profile that is delicate and fragrant, with flavors reminiscent of tea-like qualities [5]. The removal of the fruit before drying often results in brighter acidity [6].

The Natural Process: Embracing Fermentation

In contrast, the natural process, also known as the dry process, involves drying the coffee cherries whole with the fruit intact. This allows for a more extended and complex fermentation phase as the sugars and compounds within the fruit pulp interact with the bean. Studies have shown that both aerobic and anaerobic fermentation treatments can positively influence pH and acidity levels, with some treatments leading to a contrastingly less inhibitory effect [2]. This extended interaction can mellow out some of the sharper acidic notes, contributing to a richer, often fruitier, and sometimes wine-like flavor profile. While not always explicitly detailing acidity reduction, the goal of these fermentation protocols is to enhance coffee quality and consumer satisfaction, suggesting a deliberate manipulation of the final taste [2]. Specific important flavor compounds identified in related contexts, such as those from coffee pulp wines, include phenylethyl alcohol and hexanoic acid ethyl ester, which can impart sweet apple and brandy-like notes, respectively, potentially rounding out the perceived acidity [4].

Beyond the Big Two: Nuances in Processing

While washed and natural processes are foundational, variations and other methods also exist. For instance, honey processing involves a partial removal of the mucilage, creating a spectrum between washed and natural. The degree of mucilage left on the bean can influence the fermentation process and, consequently, the final acidity. Coffea arabica co-products, for example, have been observed to have lower pH values compared to Coffea canephora co-products, though the specific processing method’s role in this differential requires further exploration [3]. Understanding these subtle distinctions is key to appreciating the diverse flavor profiles achievable through different processing techniques.

In conclusion, for those seeking a coffee that is naturally mellower and lower in acidity, processing methods that allow for controlled, potentially longer fermentation periods, such as the natural process, tend to be more conducive to this profile. The way the coffee cherry is handled after harvest profoundly shapes its destiny in the cup, offering a rich tapestry of flavors influenced by the subtle art of fermentation and drying.

References

[1] — Ernesto Illy, Luciano Navarini — Neglected Food Bubbles: The Espresso Coffee Foam. — 2011-Sep — https://pubmed.ncbi.nlm.nih.gov/21892345/ [2] — Gustavo Galarza, Jorge G Figueroa — Volatile Compound Characterization of Coffee ( — 2022-Mar-21 — https://pubmed.ncbi.nlm.nih.gov/35335365/ [3] — 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/ [4] — 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/ [5] — Laudia Anokye-Bempah, Timothy Styczynski, Natalia de Andrade Teixeira Fernandes, Jacquelyn Gervay-Hague, William D Ristenpart, Irwin R Donis-González — The effect of roast profiles on the dynamics of titratable acidity during coffee roasting. — 2024-Apr-08 — https://pubmed.ncbi.nlm.nih.gov/38589450/