The Alchemy of Processing: How Coffee's Acidity and Body Are Forged

Question: How do processing methods affect the acidity and body of a coffee?

The journey from cherry to cup is a testament to transformation, where various processing methods act as alchemists, profoundly influencing coffee’s inherent acidity and body. These stages are not merely about drying and sorting; they are intricate chemical and physical processes that dictate the final sensory profile of our beloved beverage [1, 2]. Understanding these transformations offers a deeper appreciation for the complexities found in each brew.

Fermentation: The Crucible of Acidity

Fermentation, a cornerstone of many coffee processing methods, plays a critical role in developing acidity and complex volatile compounds. Aerobic and anaerobic fermentation treatments have been shown to positively influence pH and acidity levels, as well as the concentration of various volatile compounds that contribute to aroma and flavor [1]. For instance, a process involving the removal of pulp and mucilage before drying, a common method, is linked to the acidity of the fermentation medium, which in turn affects microbial growth [5]. This microbial activity during fermentation can lead to the production of organic acids and esters, directly impacting the perceived tartness and brightness of the coffee bean [3]. The specific duration and conditions of fermentation, such as the presence or absence of oxygen, can lead to distinct differences in the final acidity profile [1].

Roasting: Unlocking Flavor and Modifying Acidity

While often considered a separate stage, roasting is intrinsically linked to the success of prior processing methods and significantly impacts acidity and body. Roasting profiles dynamically alter titratable acidity. Studies have demonstrated that different roasting profiles can lead to increases in acidity. The intensity and duration of roasting influence the degradation of acids and the formation of new flavor compounds [6]. Furthermore, brewing temperature and roast level are critical in the extraction of compounds that define coffee’s characteristics. Hotter brewing temperatures and darker roasts tend to extract more compounds, potentially influencing both acidity and body by altering the solubility of various chemical constituents [7]. This implies that while processing lays the groundwork, roasting is where much of the final acidity is revealed or modified.

Beyond Fermentation and Roasting: Other Influences

While fermentation and roasting are primary shapers, other aspects of processing and the coffee bean itself contribute to the final sensory attributes. The type of coffee, such as Coffea arabica versus Coffea canephora, can exhibit different pH values, with Arabica generally having lower pH values (4.22-4.42) compared to Canephora (5.90-5.97) [2]. The preparation of co-products, like cascara or silverskin, also shows variations in water activity and pH, hinting at how even post-harvest by-products are influenced by initial processing [2]. Ultimately, the interplay of these factors creates the diverse spectrum of coffee flavors, where acidity and body are integral components of a rich sensory tapestry.

In conclusion, the processing methods employed, from the initial fermentation stages to the final roasting profiles, are fundamental in sculpting the acidity and body of coffee. These techniques are not merely mechanical steps but carefully orchestrated processes that unlock the bean’s chemical potential, directly translating into the nuanced and varied sensory experiences we cherish in our daily cup.

References

[1] — Gustavo Galarza, Jorge G Figueroa — Volatile Compound Characterization of Coffee ( — 2022-Mar-21 — https://pubmed.ncbi.nlm.nih.gov/35335365/ [2] — 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/ [3] — 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/ [4] — 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/ [5] — Claudia Gonzalez Viejo, Eden Tongson, Sigfredo Fuentes — Integrating a Low-Cost Electronic Nose and Machine Learning Modelling to Assess Coffee Aroma Profile and Intensity. — 2021-Mar-12 — https://pubmed.ncbi.nlm.nih.gov/33809248/ [6] — 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/ [7] — Niny Z Rao, Megan Fuller, Meghan D Grim — Physiochemical Characteristics of Hot and Cold Brew Coffee Chemistry: The Effects of Roast Level and Brewing Temperature on Compound Extraction. — 2020-Jul-09 — https://pubmed.ncbi.nlm.nih.gov/32659894/