Exploring the Science of Coffee Brewing: A New Control Chart for Better Flavour and Consumer Satisfaction
Article: “A new Coffee Brewing Control Chart relating sensory properties and consumer liking to brew strength, extraction yield, and brew ratio,” Jean-Xavier Guinard et al., Food Science; 2023; Volume 88, Issue 5: Pages 2168-2177. https://doi.org/10.1111/1750-3841.16531
We dive into a study that redefines how coffee professionals and enthusiasts approach brewing. The study, conducted by Guinard and colleagues and published in the Journal of Food Science, introduces a new Coffee Brewing Control Chart designed to enhance the relationship between brewing parameters and the sensory experience of coffee, with an eye toward maximising consumer satisfaction.
For decades, brewing control charts have helped baristas navigate extraction levels and concentration to reach desirable flavours. The conventional chart links Total Dissolved Solids (TDS) and Extraction Yield (EY), aiming to steer brewers toward a balanced cup without delving deeply into flavour nuances or individual consumer preferences. Guinard's team, however, found that taste perception and preference are far more complex and that a more tailored, sensory-focused chart could be instrumental for baristas and home brewers alike. Their updated chart introduces a broader and more consumer-centred perspective by providing a nuanced understanding of how TDS and EY affect specific sensory attributes like acidity, bitterness, sweetness, and overall liking.
The article is free to access and it is worthwhile opening to see the charts. I will not recreate the images here, but you can use this summary as a quick overview and aid your understanding of the article.
Key Study Parameters and Findings
The study involved an extensive sensory evaluation of coffee brewed under a wide range of TDS and EY conditions. Researchers brewed multiple batches, controlling TDS and EY levels to identify a spectrum of flavours from highly acidic and sour to intensely bitter. They used a trained sensory panel to quantify the flavours and aromas in each sample, alongside consumer testing to capture preference data.
1. Total Dissolved Solids (TDS) and Extraction Yield (EY): Fundamental Metrics
TDS measures the concentration of coffee solubles in the brew, influencing the strength and mouthfeel. A higher TDS often results in a more robust, intense cup, while a lower TDS produces a lighter, milder experience.
Extraction Yield reflects the percentage of soluble coffee material extracted from the grounds, impacting flavour complexity. Lower EY can yield a lighter, more acidic cup, while higher EY may introduce darker, more bitter notes.
By adjusting these parameters, the study found significant shifts in sensory attributes, demonstrating the need to understand the balance between TDS and EY for different flavour preferences.
2. Sensory Attributes and Consumer Preferences
The study categorised flavours based on TDS and EY, observing consistent changes in sweetness, bitterness, acidity, and aftertaste with different brewing conditions.
High EY & High TDS: These brews tended to be intensely bitter and strong, appealing to consumers who enjoy a full-bodied, robust profile but less preferred by those seeking a balanced flavour.
High EY & Moderate TDS: A sweet spot for many consumers, balancing acidity with moderate bitterness and good body. These brews retained flavour complexity without overwhelming bitterness.
Moderate EY & Low TDS: Resulted in a lighter, more delicate brew. The acidity was more pronounced, and sweetness was mild, appealing to consumers who prefer a milder, fruitier cup.
Low EY & Low TDS: Yielded a weak, under-extracted brew with an astringent aftertaste, often perceived as flat and unsatisfactory by consumers.
The researchers identified that consumer satisfaction was highest in the moderate EY, moderate TDS range, aligning well with balanced flavours of mild acidity, subtle sweetness, and low bitterness. However, consumer preference also showed variability, highlighting that while the moderate range was broadly popular, individual taste differences play a significant role.
[If, by this point, you are feeling confused as to how you apply the concept of adjusting TDS and EY to achieve the flavours you want, do not let that distract from your uptake of the information. I will in the future create recipes using various brewing methods to show how this can be done.]
3. Redefining the Sweet Spot: A New Optimal Range
Guinard and colleagues proposed a new "optimal range" on the brewing control chart. Instead of simply steering brewers toward a narrow window of EY and TDS, the updated chart emphasises a broader range that accommodates varied sensory experiences:
Acidic and Fruity Lovers: Encouraged to brew at the lower end of the TDS and EY spectrum for a brighter, more acidic coffee with fruity undertones.
Balanced Brew Enthusiasts: Positioned in the middle, where moderate TDS and EY yield a well-rounded, mildly sweet, and lightly acidic cup.
Robust Coffee Seekers: Suggested to brew with higher TDS and EY levels, resulting in a fuller-bodied, bittersweet flavour that maintains richness without over-extraction.
This expanded optimal range empowers baristas and coffee lovers to experiment with brewing variables, finding a combination of TDS and EY that aligns with their individual flavour preferences rather than adhering strictly to traditional guidelines.
4. Implications for Specialty Coffee and Beyond
This study’s implications reach beyond simply crafting the "perfect cup." By aligning sensory attributes with consumer preferences, the study promotes a more inclusive approach to coffee brewing, catering to diverse tastes. Specialty coffee shops can adopt this new chart to offer a wider range of flavour profiles, helping customers discover their preferences through guided tastings. Home brewers, too, benefit from the ability to tune their coffee’s flavour with precision, knowing that they are working within a scientifically optimised framework.
5. Further Research Directions and Practical Applications
Guinard's team suggests future research could investigate other variables, like grind size and water chemistry, to further refine the brewing control chart. The current chart sets a foundation, emphasising the importance of adjusting brewing parameters to create a personalised coffee experience. Specialty coffee shops and baristas can use these insights to guide customers through an array of profiles, enhancing the overall coffee experience and encouraging more experimentation.
Conclusion: A Step Forward for the Science of Brewing
The revised Coffee Brewing Control Chart by Guinard et al. is a powerful tool for both coffee professionals and enthusiasts, bridging the gap between extraction science and sensory preference. By mapping specific TDS and EY levels to taste profiles, the study offers a clearer pathway to satisfying a variety of palates. Whether you’re looking for a bright, fruity cup or a deeply rich, full-bodied experience, this new control chart gives you the tools to tailor your brew to perfection. As the study suggests, coffee is an inherently personal experience—this new approach to brewing simply brings us closer to capturing the flavours that resonate most with each individual.
For those passionate about coffee, Guinard’s work is a reminder of the vast potential within each brew, inviting you to explore new dimensions of taste through the science of extraction.
