The world of specialty coffee is increasingly using concepts that, just a few years ago, sounded like the hermetic language of laboratories. Among them, two recurring concepts are constantly being used: TDS and extraction. While they sound technical, they are actually key to understanding why one cup tastes delicious while another leaves you wanting more. It's the science of taste presented in a practical, at-home format—knowledge that can transform the way we approach everyday 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 "thick" the coffee tastes. A high TDS indicates an intense, full-bodied, and concentrated brew. A low TDS indicates a light, more watery cup. In the world of professional cupping and specialty coffee shops, TDS is measured with a refractometer, which allows you to assess how thoroughly the coffee has been brewed.
However, we don't need laboratory equipment to understand its significance. TDS is the sum of all the flavors transferred from the beans to the water. In practice, it is influenced by the grind size, coffee-to-water ratio, brewing time, and extraction technique. These factors determine whether a cup will be as intense as a short, strong brew from a coffee pot, or as light and pure as a filter .
Extraction – or how flavor dissolves
Extraction is the process of dissolving the chemical compounds contained in coffee beans. This process determines the balance between sweetness, acidity, and bitter notes. Coffee flavor develops in waves: fruit acids dissolve first, followed by sweetness and sugars, and finally, bitterness and heavier compounds.
If we stop the process too early, we end up with underextracted coffee: acidic, thin, and often rough. If we leave it too long, we end up with overextracted coffee: bitter, flat, and lacking pleasant sweetness. The ideal extraction point is where all elements are in harmony, and the brew becomes balanced and multi-dimensional.
How do TDS and extraction work together?
Although TDS and extraction are different measures, they come together in the same cup. TDS tells us how many flavoring substances have dissolved in the water. Extraction tells us which substances were present and in what proportions. Therefore, we can have a coffee with a low TDS but a well-balanced flavor. We can also have an intense, yet bitter and unpleasant brew if the extraction was too aggressive.
For baristas, this is the perfect pairing: TDS allows for consistency, while extraction assesses the perceived flavor quality. At home, intuition and simple rules are all you need to master both parameters without any equipment.
How to use this knowledge in practice?
The most important tools you always have on hand are grinders, water, and time. Too fine a grind and a long pour-over time will increase extraction and TDS , leading to bitterness. Too coarse a grind and a short pour-over will reduce both parameters, resulting in a flat and acidic brew. The ratio also matters: more coffee to water will increase TDS, but it won't always improve balance.
A good starting point is the classic 1:16 ratio for drip coffee and a medium grind. From there, you can experiment: shorten the time if the coffee is too heavy; grind finer if the sweetness is lacking; slightly increase the dose if the brew is too light. Each change is a micro-experiment that teaches you to act consciously rather than brewing by feel.
Science that strengthens craft
TDS and extraction aren't dry definitions—they're both language for describing flavor and tools for creating better coffee. They ensure that the result isn't a matter of chance, but rather a consequence of the decisions you make during brewing. They turn your daily cup into a small laboratory, where every change leads to a new sensory experience.
Understanding these concepts transforms specialty coffee from a secret accessible only to professionals to an art form you can develop in the comfort of your home, cup by cup.
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