The world of specialty coffee is increasingly using terms that, just a few years ago, sounded like the hermetic language of laboratories. Among them, two constantly reappear: TDS and extraction. While they sound technical, they are actually key to understanding why one cup tastes excellent and another leaves something to be desired. This is the science of taste presented in a practical, home-friendly form – knowledge that can change the way we look at daily brewing.
What exactly is TDS?
TDS, or Total Dissolved Solids, is the percentage of dissolved substances in the finished brew. Simply put: it indicates how "dense" the coffee tastes. High TDS means an intense, full-bodied, concentrated brew. Low TDS means a light, more watery cup. In the world of professional cupping and specialty cafes, TDS is measured with a refractometer, which allows for an assessment of how precisely the coffee was brewed.
However, we don't need laboratory equipment to understand its significance. TDS is the sum of all flavors transferred from the beans to the water. In practice, this is influenced by grind size, coffee-to-water ratio, brewing time, and extraction technique. It's thanks to these that we decide whether the cup will be as essential as a short, strong brew from a Moka pot, or light and clean like a brew prepared with filter coffee.
Extraction – or how flavor dissolves
Extraction is the process of dissolving chemical compounds contained in coffee beans. It determines the balance between sweetness, acidity, and bitter notes. The flavor of coffee develops in waves: first, fruit acids dissolve, then sweetness and sugars, and finally – bitterness and heavier compounds.
If we stop the process too early, we get under-extracted coffee: sour, thin, often harsh. If it lasts too long – over-extracted: bitter, flat, lacking pleasant sweetness. The ideal extraction point is where all elements remain in harmony, and the brew becomes balanced and multidimensional.
How do TDS and extraction work together?
Although TDS and extraction are different measurements, they meet in one cup. TDS tells us how many flavor substances have dissolved in the water. Extraction tells us what those substances were and in what proportions. So, we can have coffee with low TDS but well-balanced. We can also have an intense brew that is bitter and unpleasant if the extraction was too aggressive.
For baristas, it's a perfect duo: TDS allows for assessing consistency, while extraction assesses the quality of the perceived flavor. At home, intuition and simple rules are enough to master both these parameters without equipment.
How to apply this knowledge in practice?
The most important tools you always have at hand are your grinder, water, and time. Grinding too fine and a long pour-over time will increase extraction and TDS, leading to bitterness. Grinding too coarse and a short pour-over will lower both parameters – the brew will become flat and sour. Ratios also matter: more coffee relative to water will increase TDS, but it won't always improve balance.
A good starting point is the classic 1:16 for pour-over coffees and a medium grind. Then you can experiment: shorten the time if the coffee is too heavy; grind finer if it lacks sweetness; slightly increase the dose if the brew is too light. Each change is a micro-experiment that teaches you how to act consciously instead of brewing "by feel."
Science that strengthens craftsmanship
TDS and extraction are not dry definitions – they are a language that can describe taste, and at the same time, tools that help create better coffee. They provide assurance that the outcome is not a matter of chance, but a consequence of the decisions you make during brewing. Thanks to them, your daily cup becomes a small laboratory where every change leads to a new sensory experience.
Understanding these concepts makes specialty coffee cease to be a mystery accessible only to professionals. Regardless of whether you choose filter beans or espresso coffee, it becomes an art that you can develop in the comfort of your home – cup by cup.
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