The Flavor Truth Behind TDS and Extraction Yield：The Interplay of Grind Size, Water Temperature, and Brewing Techniques
In the world of pour-over coffee, TDS (Total Dissolved Solids) and extraction yield are two commonly used objective metrics to measure the results of extraction. However, even with the same TDS and extraction yield, the final flavor profile can still differ significantly. This experiment was designed to explore that very phenomenon. Using the same batch of coffee — Panama Hacienda La Esmeralda Red Label Special Porton Natural Geisha, Light Roast — we performed pour-over brews under two different conditions, achieving identical TDS and extraction yield, and observed the resulting differences in flavor.
Condition 1: Fine Grind + Low Water Temperature + Continuous Pouring
Grind Setting: Mahlkönig EK Omnia at 450 (finer grind)
Water Temperature: 80°C (lower temperature)
Pouring Method: Continuous, steady pour without stopping
Final Brew TDS: 1.25, Extraction Yield: 17.5%
● Tasting Notes
At High Temperature: Peach, berries; delicate sweet-tart acidity with a smooth mouthfeel
At Medium Temperature: Lychee, safflower
At Low Temperature: Peach, lychee, grape; bright acidity with a delicate, clean texture and minimal graininess
Under this set of conditions, the flavor profile showcased a delicate, clean, and elegant floral-fruity character. The mouthfeel was focused, with an overall presentation that was refined and well-balanced.
● Underlying Logic
A finer grind means a larger total surface area, allowing water to interact more thoroughly with the coffee grounds. If paired with a typical high brewing temperature, it can easily lead to over-extraction and result in bitterness. Lowering the water temperature helps slow down the rate of extraction, preventing excessive dissolution and keeping the overall extraction within the ideal range. In other words: a finer grind increases extraction potential, while a lower water temperature balances this potential, allowing the extraction yield to remain stable and the flavors to stay clean, delicate, and well-defined.
Condition 2: Coarse Grind + High Water Temperature + Pulse Pouring
Grind Setting: Mahlkönig EK Omnia at 550 (coarser grind)
Water Temperature: 95°C (higher temperature)
Pouring Method: Pulse pouring in four pours
Final Brew TDS: 1.25, Extraction Yield: 17.5%
● Tasting Notes
At High Temperature: Plum, peach; pronounced sweetness with a heavy, slightly bitter finish
At Medium Temperature: Grape, peach
At Low Temperature: Grape juice, safflower, lychee; balanced acidity and sweetness, with a more open texture and noticeable graininess
Under this set of conditions, the flavor profile appeared more layered and open, with a stronger sweetness but also a more noticeable bitter aftertaste. The mouthfeel was broader, with distinct layers, though slightly lacking in clarity and refinement.
● Underlying Logic
A coarser grind means larger particles and less total surface area, which slows down the release of soluble compounds within a given time. To compensate, a higher water temperature is needed to improve extraction efficiency. Additionally, pulse pouring allows the coffee bed to be fully saturated and redistributed, helping to release compounds more evenly during later stages of extraction. However, the combination of high temperature and pulse pouring increases the risk of over-extraction, which can result in bitterness and a heavier, less clean finish.
Comparison Summary
This experiment demonstrated that even with identical TDS and extraction yield, variations in grind size and water temperature can create distinctly different flavor profiles. A finer grind combined with lower water temperature helps control the risk of over-extraction, resulting in a stable and delicate cup. On the other hand, a coarser grind paired with higher water temperature improves the efficiency of soluble extraction, but also increases the potential for flavor variability.
Both approaches can achieve “perfect numbers” on paper, yet tell entirely different stories in the cup. This is precisely the charm of pour-over coffee — it’s not just about chasing precise data, but about exploring the unique conditions and possibilities behind every flavor experience. A cup of coffee with TDS 1.25, carrying two very different souls.
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