The Elusive Bitterness: How Brew Time Fine-Tunes Your Coffee's Character

Question: What’s a simple change in my brew time that can significantly alter the bitterness of my coffee?

The quest for the perfect cup of coffee often involves a delicate balance of factors, from bean origin to roast level. However, one of the most accessible yet impactful adjustments a home brewer can make is to manipulate the brew time [7]. This seemingly simple variable holds substantial power to alter the perceived bitterness of your coffee, a characteristic deeply intertwined with the extraction of various soluble compounds [7, 5].

The Science of Extraction and Bitterness

At its core, brewing coffee is an exercise in extraction. Hot water acts as a solvent, dissolving the myriad of chemical compounds present in roasted coffee grounds. These compounds include acids, sugars, lipids, and importantly, various phenolic compounds and alkaloids responsible for bitterness [2, 5]. As brew time increases, the contact between water and coffee grounds is extended, allowing for a greater volume of these soluble substances to be drawn into the liquid [7].

Early in the brewing process, acids and lighter flavor compounds tend to extract first, contributing to a brighter, more acidic cup. As the brew progresses, more complex compounds begin to dissolve, including those that impart sweetness and, eventually, bitterness. Chlorogenic acids, for instance, are known contributors to coffee’s flavor profile and can break down into more bitter compounds during the brewing process [5]. Therefore, extending the brew time past an optimal point can lead to an over-extraction of these bittering agents [7].

Brew Time and Method: A Synergistic Relationship

The impact of brew time on bitterness is not uniform across all brewing methods. Full immersion methods, such as French press or cold brew, where coffee grounds are steeped directly in water for an extended period, are particularly susceptible to the influence of brew time [7]. In these methods, the longer the coffee steeps, the more opportunity there is for bitter compounds to accumulate [7].

For example, studies on full immersion brewing have shown how flavor profiles evolve over time, with sourness, berry, and citrus notes being strongly linked to titratable acidity, while bitterness often emerges with prolonged contact [7]. Conversely, brewing methods that involve continuous water flow, like pour-over or drip coffee, have a more controlled extraction rate, where the water is in contact with the grounds for a shorter and more defined period. Even in these methods, however, extending the brew cycle by slowing down the water flow can lead to a more bitter result.

Optimizing for Bitterness

Understanding the relationship between brew time and bitterness allows for intentional adjustments. To reduce bitterness, a shorter brew time is generally recommended. This limits the extraction of the compounds that contribute to a bitter taste [7]. Conversely, if a more pronounced bitter character is desired, extending the brew time, within reason, can achieve this [7]. It is important to note that excessive brew times can lead to an unpleasant, harsh bitterness due to the over-extraction of a wide range of undesirable compounds.

While other factors like grind size, water temperature, and coffee-to-water ratio significantly influence extraction and flavor, brew time offers a readily adjustable lever for fine-tuning bitterness. By simply adjusting how long your coffee grounds steep, you can command a noticeable shift in the final cup’s flavor profile, moving it towards or away from the realm of bitterness.

In conclusion, the duration your coffee steeps in water is a potent tool for controlling bitterness. A shorter brew time favors brighter, less bitter notes, while a longer steeping period encourages the extraction of more soluble compounds, including those that contribute to bitterness. Mastering this variable allows for a more nuanced and personalized coffee experience.

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] — Jiexin Liang, Mackenzie E Batali, Catherine Routt, William D Ristenpart, Jean-Xavier Guinard — Sensory analysis of the flavor profile of full immersion hot, room temperature, and cold brewed coffee over time. — 2024-Aug-20 — https://pubmed.ncbi.nlm.nih.gov/39164402/