The Influence of Processing on Coffee's Brightness and Acidity: A Sensory Exploration

Question: How do different processing methods affect the perceived acidity or brightness of a coffee?

The journey from bean to cup involves a series of intricate processes, each capable of shaping the final sensory experience of coffee. Among the most impactful of these are the processing methods employed, which can significantly influence the perceived acidity and brightness of a brew [2, 4, 6]. Understanding how these methods interact with the coffee bean’s inherent chemistry is key to unlocking a nuanced appreciation for this beloved beverage.

Fermentation’s Role in Acidity

Fermentation is a critical stage where microorganisms break down sugars and organic acids within the coffee cherry. Research indicates that specific fermentation protocols can directly enhance coffee quality and consumer satisfaction by positively influencing pH, acidity, and the concentration of volatile compounds [2]. For instance, both aerobic and anaerobic fermentation treatments have demonstrated beneficial effects on these attributes, contrasting with the inhibitory impact observed in treatments involving only CO₂ [2]. The duration and conditions of fermentation, such as temperature and pH levels, are crucial parameters that dictate the resulting acidity profile [2].

Processing Methods and Their Impact on Flavor

The physical removal of the coffee cherry pulp before drying, a common processing step, is associated with contributing to bright, tangy flavors in coffee [6]. This method, often referred to as a washed process, can lead to distinct sensory characteristics compared to other approaches. While specific parameters are not detailed, the general principle suggests that altering the external layers of the bean prior to drying can influence the development of desirable flavor precursors and, consequently, the perceived acidity and brightness [6].

Roasting’s Influence on Titratable Acidity

Beyond initial processing, the roasting phase is equally instrumental in defining coffee’s acidity. Roast profiles meticulously manage temperature and time to influence the dynamics of titratable acidity. Different roasting strategies can lead to varied levels of acidity, a fundamental component of a coffee’s perceived brightness and tang [7]. The complex interplay between the bean’s chemical composition and the thermal energy applied during roasting dictates how these acids manifest in the final cup.

Co-Products and Varietal Differences

Even the by-products of coffee processing, such as cascara and silverskin, exhibit variations in pH influenced by the coffee varietal. For example, Coffea canephora co-products tend to have higher pH values (5.90-5.97) compared to Coffea arabica (4.22-4.87) [3]. While this pertains to co-products, it highlights how the inherent genetic makeup of different coffee species can predispose them to different acidity levels, which processing further modifies.

In conclusion, the perception of acidity and brightness in coffee is not solely an intrinsic characteristic of the bean but a dynamic outcome shaped by a confluence of processing techniques. From the controlled environment of fermentation to the transformative heat of the roaster, each step plays a vital role in orchestrating the complex symphony of flavors, with acidity and brightness acting as key conductors.

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] — 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] — Verônica Belchior, Bruno G Botelho, Adriana S Franca — Comparison of Spectroscopy-Based Methods and Chemometrics to Confirm Classification of Specialty Coffees. — 2022-Jun-04 — https://pubmed.ncbi.nlm.nih.gov/35681405/ [7] — 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/