How to Use ATAGO TDS Meter? How to Calculate Golden Cup Extraction | Coffee Extraction

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Today, a fan asked FrontStreet Coffee how to use a coffee TDS measuring instrument. So today, FrontStreet Coffee will share with you how this instrument is used and what its purpose is.

Coffee Concentration Meter

It actually uses the principle of light refraction to measure the total dissolved solids in water.

We can see that the concentration meter displays: Brix, TDS.

Brix: The concentration of soluble solid components contained in the sample. Soluble solid components refer to all substances dissolved in water, such as sugar, salt, protein, acid, etc.

TDS: The ratio between soluble substances and water in a cup of coffee. The higher the TDS value, the more dissolved substances are contained in the water.

FrontStreet Coffee has given you a general introduction to the coffee concentration meter. Next, we will demonstrate how to use this meter:

How to Use the Coffee Concentration Meter

1. Press "START" to turn on the machine, drop pure water onto the refractometer crystal, and press "ZERO" to calibrate;

2. After stirring the brewed coffee evenly, immediately take about 1g of liquid and let it sit for about a minute to allow the coffee liquid temperature to decrease, then drop it onto the refractometer crystal, press "START" to begin detection, and wait a few seconds for the results to appear.

Remember to clean it with water or alcohol after use~

Understanding Extraction Rate

So what use are these values to us? After measuring these parameters, we can calculate the extraction rate of coffee!

Extraction Rate: Indicates the proportion of weight lost by coffee beans during the brewing process relative to the amount of coffee beans used. Simply put, it's about what proportion of substances from the coffee grounds used for brewing are dissolved into the coffee.

For example, when you use 100g of coffee grounds for brewing, after the coffee is brewed, when the moisture in the coffee grounds is removed (whether dried or sun-dried), if 80g remains, it means that 20g of substances have been dissolved into the coffee, so the extraction rate of this coffee is 20%.

The Golden Cup Theory

In the world of coffee, there is a concept called: Golden Cup Theory!

In actual coffee extraction, to pursue better coffee taste, one must strive for both the original flavor of coffee and avoid producing bad flavors. There are several widely recognized standards for the trade-off ratio in this balance, which is the legendary Golden Cup theory.

The Golden Cup Theory believes that "delicious coffee" must meet two conditions simultaneously:

1. Extraction rate between 18% and 22%

2. Coffee concentration within the range of 1.2% to 1.45%

Calculation formula: (Coffee liquid weight × TDS%) ÷ Coffee ground weight = Extraction Rate

Under-extracted coffee (extraction rate below 18%) usually has a sour, thin, and bland taste, monotonous without characteristics; over-extracted coffee (extraction rate above 22%) becomes increasingly bitter, ashy, and astringent.

For drip coffee, simply put, a coffee-to-water ratio between 1:15-1:22 can generally be called the Golden Cup range, but this does not mean that this ratio is the Golden Cup.

In addition, the coffee-to-water ratio is not equal to the coffee-to-liquid ratio, and certainly not equal to concentration. Conversely, the standard Golden Cup coffee-to-water ratio will basically fall within the above range~

Important Notice :

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