The Impact of Pour-Over Coffee Extraction Time and a Brief Analysis of TDS Effects on Coffee Extraction

FrontStreet Coffee - Analysis of TDS and Extraction Time's Impact on Coffee Extraction

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Acidic substances are relatively light or small, allowing them to extract significant values in a relatively short time.

Aroma and flavor, due to their proportion in the coffee itself, closely follow the acidity to reach the peak of extraction intensity.

Fine coffee particles play an important role in the secondary peak of aroma and flavor extraction.

Substances with a fuller body or sweetness require longer extraction times to become prominently expressed.

Once a certain type of coffee substance reaches its extraction intensity peak, the expression of other substance types will be masked (hence the sensation of sweetness increasing while acidity decreases).

Compared to acidic substances, sugar particles have larger volumes, so their extraction speed is slower (or they require longer time to be extracted).

In simple terms, small flavor particles can be quickly dissolved and carried into the coffee liquid, while larger substances extract more slowly. Therefore, by controlling the brewing time, you can determine the ratio of small to large particles in the coffee liquid, which in turn decides the proportion of flavor or mouthfeel presentation.

During the brewing process, if you want to highlight sweetness, you can try extending the brewing time to allow sweet substances sufficient time to be extracted; if you want to emphasize acidity, you can try shortening the brewing time; if there are bitter flavors in the coffee that you don't like, you can also try reducing the brewing time.

The Role of Water Quality in Coffee Extraction

TDS is a key indicator recommended by SCA for measuring water quality in the coffee industry. It should be between 75-250 mg/L, with a target TDS value of 150. TDS can measure any minerals, salts, metals, or other solids dissolved in water. The mineral concentration in water is an important taste-influencing factor that can have both negative and positive effects depending on the minerals and their concentration, and significantly affects extraction. Water hardness refers to the concentration of specific minerals in water: calcium, magnesium, iron, and manganese, as well as some other minerals in smaller amounts. In other words, water hardness is part of TDS, and high TDS typically indicates hard water.

pH value also plays a crucial role in coffee extraction. We learned in middle school textbooks: if the pH value is 7.0, water is neutral; if the pH value is higher than this, it's alkaline; if it's lower than this, it's acidic.

In coffee extraction, the more neutral the water, the better. SCA recommends that the optimal pH value for water used in coffee should be between 6.5 and 7.5.

As hydrogen (H+) ions increase, the pH value of water decreases, meaning it has higher acidity. When a large amount of hydroxide (OH-) ions are present, water becomes alkaline, which can lead to bitter taste in water.

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