What is TDS in coffee
Total Dissolved Solids is an indicator that reflects the total amount of dissolved substances in coffee. This is everything that has passed from the ground beans into the water: oils, acids, sugars, microparticles. It is measured as a percentage (%) or ppm (parts per million). For example, 1.3% TDS means that 1.3% of the volume is dissolved substances, and the rest is water. Typical values for espresso are 8-12%, for filter coffee – 1.1-1.5%.
What is the coffee extraction level
Extraction is a process where water extracts soluble substances from ground coffee beans. This is how we get the flavor, aroma and body of the drink. When we brew the grind, some of the substances are transferred to the water: first acids and fruity notes, then sweetness, and then bitterness and tannins. There are three levels of extraction:
- Low extraction level (less than 18%) – coffee is under-extracted. The drink will be sour and watery.
- The optimal level (18-22%) is a well-balanced drink: sweetness, acidity and light bitterness in harmony.
- High level (over 22%) – overcooked. It may have excessive bitterness, dryness and an unpleasant aftertaste.
At the same time, each brewing method has its own ideal range:
- Espresso: 18-22%
- Purover (V60): 18-20%
- French press: 20-22%
- Aeropress: 18-22% (depends on the recipe)
Relationship between TDS and extraction level
TDS (Total Dissolved Solids) and Extraction Yield are closely related.
TDS is a measure of the concentration of dissolved solids in a beverage, while extraction is how much of these solids have been extracted from the beans. As the amount of dissolved solids increases, the extraction rate usually increases, but not always. An overly high value can indicate over-extraction.
This relationship is often depicted in the Coffee Brewing Control Chart, the so-called “golden triangle of coffee.”
Extraction level (%) is plotted on the horizontal axis and TDS (%) on the vertical axis. The graph is divided into sectors indicating:
- under-extraction (insufficient saturation),
- over-extraction (too bitter),
- the ideal zone – the “sweet spot” with a balance of flavor.
For example, for filter coffee, it is 18-22% extraction and 1.15-1.35% TDS.
The chart helps baristas assess the quality of the drink and fine-tune the recipe.
Impact of TDS and extraction on coffee flavor balance
Under-extraction (low levels) results in a watery beverage with a sharp acidity and lack of depth. Overexpression (over-extraction) creates a bitter, dry taste. The optimal balance is the “golden mean” when the drink has a rich body, sweetness, bright but pleasant acidity and light bitterness. Adherence to the recommended values (18-22% extraction, 1.15-1.35% TDS) allows you to unleash the full potential of the grain and achieve a harmonious flavor profile.
Principle of operation of the TDS meter
The device works on the basis of electrical conductivity technology: the more substances dissolved in water, the better it conducts current. It measures the electrical conductivity of the liquid and converts this value into ppm (parts per million), which reflects the concentration of dissolved solids.
The main components of the device:
- electrodes (usually made of stainless steel)
- microprocessor
- display.
Before measuring, the device must be calibrated, the electrodes must be rinsed, and the drink must be cooled to a temperature of 20-25 °C for accurate readings.
Methods for measuring dissolved solids and extraction levels
For accurate measurement, you will need the following tools:
- Meter
- Scales with an accuracy of 0.1 g
- Clean pipette or syringe
- Laboratory beaker
- Thermometer (optional)
A step-by-step process:
- Brew some coffee.
- Cool the drink to 20-25 °C.
- Stir and take a sample.
- Put a drop on the refractometer glass or dip the TDS meter electrode.
- Enter the value in % or ppm.
Mathematically, the sum of the substances extracted from the grains into the beverage is defined as follows:
Extraction Yield (%) = (TDS × beverage volume) / weight of ground coffee × 100
Factors affecting measurement accuracy
The calibration must be accurate, otherwise the readings will not be correct. Regular checks with calibration solutions are mandatory.
Hot or cold coffee can affect the accuracy of the readings due to changes in electrical conductivity.
Residual coffee oils, sediment, or foreign matter on the electrodes or utensils can also distort the data. It is important to use clean instruments.
The human factor also affects the accuracy of the indicators. Errors during sample collection, incorrect data reading, or incorrect calculations can affect the result. Attentiveness and consistency of action are important.
Limitations and disadvantages of the device
A TDS meter estimates the total amount of solid dissolved solids, but does not distinguish between their chemical composition. For example, minerals from water and extracted compounds from coffee are counted together, which can lead to inaccurate mineralization measurements.
TDS is calculated based on electrical conductivity, but not all substances conduct current in the same way, so a drink can have the same number of dissolved particles but taste different due to differences in composition. To fully evaluate coffee, it is important to combine the measurement with sensory analysis, as it is only one quality parameter and does not take into account aroma, texture, or aftertaste.
Ways to manage the level of dissolved solids
You can adjust the grind level, water temperature, brewing time, and equipment to suit your preferences or specific requirements.
A finer grind increases the area of contact with water, increasing the indicators, while a coarser grind, on the contrary, reduces them. A higher temperature activates the dissolution of substances, increasing TDS, while a lower temperature reduces the degree of grain opening.
Extending the time the grinds are in contact with water increases the level, while shortening it decreases it.
Coffee machines, filters, kemexes and geysers have different effects on brewing and grounds concentration, so their choice is equally important for controlling the indicator.
Control methods
One of the easiest ways to control the delicate harmony of the coffee palette is to get the grind to water ratio right. Increasing the amount of coffee or decreasing the amount of water increases the concentration of dissolved substances and the level of extraction, and vice versa.
It is equally important to pay attention to the brewing technique. How you pour the water, how fast you pour it, how evenly you pour it – all of this affects the taste, how much flavor the coffee beans will give off. Each method of brewing (espresso, pour-over, aeropress, or French press) has its own characteristics, and they bring out the coffee in different ways. Experimenting with methods gives you a better understanding of how to control the extraction.
And, of course, we should remember the grain. Even the most sophisticated equipment won’t save a drink made from poor raw materials. Freshness, roasting, and quality of beans are the basis without which control over the brewing process is simply impossible.
Improving the quality of coffee water
Optimal water for coffee has a neutral pH (6.5-7.5), moderate hardness and low chlorine content. For purification, activated carbon filters, reverse osmosis or ultrafiltration are used to remove impurities and unpleasant odors. An excess of calcium and magnesium improves flavor and brewing, but too much hard water can make coffee bitter. Water with the right balance of minerals is selected for different varieties and brewing methods to bring out the unique flavor of the drink.
Practical tips for the home barista
Measure dissolved solids and extraction regularly to understand how the parameters are changing.
Keep a brewing log, recording grind, temperature, time, and your impressions of the drink.
Experiment with different settings to find the perfect balance for your coffee.
Gradually improve your skills by analyzing your mistakes and results, as regular practice will help you achieve a consistently delicious drink.
Conclusions and key points
To make truly delicious coffee, it’s not only important to taste the flavor, but also to understand what’s behind it. Understanding the two key indicators, TDS and extraction level, opens the door to conscious coffee making. Instead of relying on chance, you start to control the process: you change the grind, time, temperature, and get a consistently perfect result.
