The silent revolution of immersion
Why full immersion brewing is the underestimated future field of sensory coffee development
Why full immersion brewing is the underestimated future field of sensory coffee development
In an industry that is increasingly defined by microbiological precision, analytical roasting profiles and data-based machine calibration, full immersion brewing almost seems like a relic. No pumps. No pressure. No complex extraction flowchart. Just ground coffee, water, time - and a filter. And yet it is precisely this simple technology that has proven to be the most precise stage for scientifically sound flavour control in recent years.
The silent revolution in coffee is not taking place in the vacuum tanks of fermentation or in the laptops of roast profile analysis - but in inconspicuous glass flasks waiting to be filtered. And what happens there is nothing less than the redefinition of what we thought we knew about extraction, flavour formation and sensory diversity.
From cupping to scientific methodology
Full immersion is not a 21st century invention. It is the origin of all sensory quality control in coffee: cupping. It was the simplest and at the same time most comparable method of assessing green coffee from different origins. However, although the process has been standardised to a certain extent - for example through the protocols of the Specialty Coffee Association - the extent to which sensory properties can actually be influenced through targeted variation of the brewing parameters remained unresearched for a long time.
Recent scientific studies, particularly those conducted by the UC Davis Coffee Center, are now revealing what was previously hidden: the astonishing versatility that can be achieved even with a single blend and within a single brewing method - simply by controlling the temperature, roast level and brewing time.
One coffee, many characters
The centrepiece of the study was a 2 × 3 × 5 experimental design. A Central American blend was used, prepared in two degrees of roast (light, medium-dark), at three brewing water temperatures (4 °C, 22 °C, 92 °C) and five extraction times (between a few minutes and 24 hours). In the end, 30 different samples were analysed physico-chemically and by a trained sensory panel.
The most surprising result: 25 of the 28 sensory attributes varied significantly between the samples. And this despite identical beans. The combination of temperature, time and degree of roasting had such a strong effect on the flavour development that the same coffee was sometimes reminiscent of a floral Ethiopian and sometimes of a dark Brazilian espresso.
Temperature in particular served as a strong multiplier of sensory effects: cold brews enhanced the perception of sweet, floral notes - especially with lighter roasts. Hot brews, on the other hand, brought out bitter notes, roasted flavours and a pronounced viscous texture. In between - at room temperature - profiles were created that were often described as balanced or ‘classic’, with fruity, earthy or chocolaty nuances.
The role of time - underestimated and re-evaluated
Contrary to expectations, the brewing time itself was not a linear amplifier of intensity. Although the total dissolved solids (TDS) increased with longer brewing time, there were increasing plateau effects at the sensory level. Some flavours continued to intensify (such as astringency or roasted notes), while others (such as fruity or floral notes) remained stable or even decreased.
Particularly interesting was the observation that the sensory profiles of certain long cold brews overlapped strongly with those of short hot brews. In other words, time and temperature are not additive, but interchangeable. If you invest enough time, you can produce similar flavours with cold water as with hot water in a shorter time - a decisive indication for product development and quality management.
TDS, yield and the misunderstanding of strength
Another key finding of the research was the close correlation between sensory intensity and brewing strength (TDS). Flavours such as bitterness, astringency, roasted aromas or smokiness increased proportionally with the TDS content - the more dissolved substances, the more intense these impressions. Interestingly, the opposite was true for sweetness, which decreased with increasing TDS.
This reveals a fundamental conflict of objectives: if you want to achieve a sensory sweet, round coffee, you must not work obsessively towards high extraction values. Instead, the interplay of TDS, extraction yield (E), temperature and degree of roasting must be harmonised in such a way that a harmonious aroma profile is created - not necessarily one that is as complete as possible.
One coffee image - many realities
What this new perspective reveals is the possibility of a sensory ‘target image’ that can be achieved regardless of the brewing method. Whether cold brew, room temperature infusion or classic hot extraction - science shows that similar flavour profiles can be reproduced through targeted control of the variables. This makes full immersion brewing a matrix, a map for sensory design.
For coffee roasters, this means that they can market the same bean with different sensory characters - depending on the brewing concept. For cafés and manufacturers: they can develop recipes that offer consistent sensory experiences despite changing green coffees. And for the industry as a whole: it gains a scalable, robust tool to systematically harmonise taste, quality and customer expectations.
Immersion as the laboratory of the future
What was long regarded as a simple cupping tool is now turning out to be a highly variable system for product development and quality assurance. The full immersion method is therefore not just a brewing technique, but a platform - scientifically analysable, sensory controllable, economically relevant.
Appendix - Literature
Another key finding of the research was the close correlation between sensory intensity and brewing strength (TDS). Flavours such as bitterness, astringency, roasted aromas or smokiness increased proportionally with the TDS content - the more dissolved substances, the more intense these impressions. Interestingly, the opposite was true for sweetness, which decreased with increasing TDS.
This reveals a fundamental conflict of objectives: if you want to achieve a sensory sweet, round coffee, you must not work obsessively towards high extraction values. Instead, the interplay of TDS, extraction yield (E), temperature and degree of roasting must be harmonised in such a way that a harmonious aroma profile is created - not necessarily one that is as complete as possible.
One coffee image - many realities
What this new perspective reveals is the possibility of a sensory ‘target image’ that can be achieved regardless of the brewing method. Whether cold brew, room temperature infusion or classic hot extraction - science shows that similar flavour profiles can be reproduced through targeted control of the variables. This makes full immersion brewing a matrix, a map for sensory design.
For coffee roasters, this means that they can market the same bean with different sensory characters - depending on the brewing concept. For cafés and manufacturers: they can develop recipes that offer consistent sensory experiences despite changing green coffees. And for the industry as a whole: it gains a scalable, robust tool to systematically harmonise taste, quality and customer expectations.
Immersion as the laboratory of the future
What was long regarded as a simple cupping tool is now turning out to be a highly variable system for product development and quality assurance. The full immersion method is therefore not just a brewing technique, but a platform - scientifically analysable, sensory controllable, economically relevant.
Appendix - Literature
- Liang, J., Batali, M. E., Routt, C., Ristenpart, W. D., & Guinard, J.-X. (2024). Sensory analysis of the flavor profile of full immersion hot, room temperature, and cold brewed coffee over time. Scientific Reports. https://doi.org/10.1038/s41598-024-69867-6
- Liang, J., Chan, K. C., & Ristenpart, W. D. (2023). An Equilibrium Desorption Model for the Strength and Extraction Yield of Full Immersion Brewed Coffee. Research Square. https://www.researchsquare.com/article/rs-127037/v1
- Guinard, J.-X., Frost, S., Batali, M., Cotter, A., Lim, L. X., & Ristenpart, W. D. (2023). A new Coffee Brewing Control Chart relating sensory properties and consumer liking to brew strength, extraction yield, and brew ratio. Journal of Food Science, 88, 2168–2177. https://doi.org/10.1111/1750-3841.16531
Author:
Dr. Steffen Schwarz
Dr Steffen Schwarz is an internationally recognised expert in the field of coffee, an entrepreneur and a lecturer.
As the founder of the Coffee Consulate in Mannheim, he has for many years been dedicated to the training and further education of professionals across the entire coffee value chain. His work combines scientific insights with practical experience and covers topics such as coffee quality, sensory analysis, sustainable cultivation, and the processing and preparation of coffee.
Drawing on his many years of expertise, he advises companies worldwide, develops training programmes for the coffee industry and is committed to the responsible and quality-oriented handling of coffee. As an author, Dr Steffen Schwarz conveys complex specialist knowledge in an accessible and practical way, offering his readers new perspectives on one of the world’s most fascinating luxury foods.