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What is a coffee refractometer?
What exactly are coffee refractometers used for?
Published August 12, 2021
Anonymous #261
Coffee experts@The Coffee Lab
The refractometer is a device that is capable of measuring the TDS (total dissolved solids) of coffee—we recommend that you opt-in for one of these devices if you take the process and extraction of coffee seriously.
Likewise, identifying the total dissolved solids allows you to know exactly how much coffee is extracted and how much caffeine concentration there is in a cup.
For this reason, the coffee industry, including folks like professional roasters and baristas, often time choose to have a refractometer at their workstation. This is because knowing the results will help them to know the correct roasting time, calibrate the grinder, estimate the amount of grinding, the extraction time, and other factors that must be adjusted to be able to correctly extract a cup of coffee.
Yes, we know that adding this tool to your coffee kit is expensive. That is why we recommend making this investment, especially if you are a coffee roaster, a professional barista or you have a specialty coffee shop and you want to obtain the best extraction quality for each coffee bean.
More you should know about coffee refractometer
Conventional refractometers are scientific tools designed to measure the refraction of light through liquids.
However, in a similar way, coffee refractometers make it possible to identify the extraction amounts and how much concentration of caffeine there is in a cup of coffee.
This means that we can measure the total dissolved solids. In other words, we can measure how much coffee is in the water in such a way that, having the data from the refractometer, the weight of the preparation and the weight of the drink, you can have more exact control of the percentage of ground coffee that was extracted during the preparation.
Why buy a coffee refractometer?
You are probably wondering who cares about this data? And why a refractometer is not going to replace the role of a professional coffee taster or barista.
On the other hand, having a coffee refractometer is useful because even the most experienced in the world of coffee can be deceived by their senses.
And having quantifiable data will help us establish a benchmark when we have to determine the quality of the coffee.
How to use a coffee refractometer
Whether you are a coffee expert or professional barista, you will always be looking for new methods, tools, or controls that allow you to obtain the best possible extraction. Additionally, you will want to achieve the best quality of flavor, aroma, and good body in your coffee.
However, just having a refractometer as one more tool in your coffee brewing kit will not guarantee us to get the perfect espresso.
We must know how to use it correctly if we want to have accurate results.
The coffee refractometer is used in a simple way. Another thing then is to know what to do or how to interpret the data that it gives you. It is useless to buy a refractometer to measure the TDS of coffee if you do not use the measurements you obtain at all. But when it comes to handling, the question is very simple
Here are some basic tips for the correct use of a coffee refractometer
- The first thing we always recommend is cleaning all our tools. For this activity, you can use a clean cloth, water and rub the eye or lens of the device. Then make sure to dry it well before using it.
- The next thing is to drop a couple of drops of coffee on the reader. The refractometer should show, after a couple of seconds, the results on the screen. Using the formula that we have explained above, you can get the TDS of the coffee, and having the volume of the drink will allow us to see the performance of the extraction.
- Finally, once we have the information, we can begin to make the necessary adjustments both in the recipe, grinding, and other factors necessary to achieve a correct extraction of the coffee.
How to calculate the TDS with a coffee refractometer
In these modern times, there are applications on our smartphones that will help us calculate the TDS of our coffee without complications. However, we believe that it is important that you know the formula to achieve these results.
What you must first do is calculate the extracted mass you obtain from the percentage of TDS and then multiply it by the weight of the extracted coffee.
Now, with that number, calculate the extraction percentage, which is the extracted mass divided by the mass of dry ground coffee.
For this, there is a simple formula:
% EXTRACTION = (TDS X BEVERAGE EXTRACTED) / MASS OF THE DOSE USED DRY
Predictable values for measuring the TDS of coffee
Do all coffees have the same TDS? Is there a standard or reference value for universal TDS? Well no. It depends on the sort of coffee you are extracting. Here are some values that could be considered "normal" depending on the type of coffee you make.
Espresso coffee (normal): about 10%
Long espresso coffee (lungo): about 5-6%
Ristretto coffee (short): about 13%
However, a more concentrated coffee will always have a higher TDS than a more diluted coffee. You will notice this at once when tasting the coffee, but what you achieve when using a refractometer is to have the exact, precise, and objective figure, which can then be used to know the % extraction with the formula that you have seen higher.
Types of coffee refractometers
1. Digital coffee refractometer
The refractometers for coffee machines are used to measure the TDS of coffee or degrees of Brix of the same.
How? Does this still sound strange to you?
Well, maybe you get to know better if we tell you that TDS stands for Total Dissolved Solids, and that Brix degrees measure the amount of sugars present in a liquid (coffee, in our case).
Knowing the TDS of coffee (or degree of solubility, how concentrated the coffee is) through a refractometer, we can know the exact amount of coffee that has been extracted, and the concentration of caffeine it has. This is the most commonly used measurement in the barista arena. With another use of the refractometer, we can also measure the amount of sugars present in our espresso.
In short, these devices serve two things:
- To measure the concentration of coffee (TDS ), and to know if it is more or less diluted in the water.
- To measure the amount of sugar in coffee ( Brix degrees ).
2. Optical refractometers for coffee
Unlike digital ones, the optical coffee refractometer has a smaller size (as if it were a very thick thermometer) and also a more affordable cost. They only serve to measure the Brix degrees (sugar concentration), not the TDS of our drink. Of course, optics tend to have a greater measuring range in Brix than digital refractometers.
3. Refractometer for a coffee machine: The RCM-1000BT
A coffee refractometer is not the same as one for wine, honey or beer, to name a few examples. There are many liquids in which we may be interested in measuring their concentration or sugars. So, when buying your refractometer for a barista, make sure it is a specific model for coffee. For example, this RCM-1000BT.
It is a digital refractometer with Bluetooth, which instantly measures both the TSD and the Brix degrees of the coffee, as well as the temperature of the coffee. What is the Bluetooth technology of this device for? Well, mainly to record and send measurements through the manufacturer's application.
The measurement ranges of this digital coffee maker refractometer are as follows:
- Brix degrees: between 0.0% and 26.0%
- TDS: between 0.0% and 23.0%
- Temperature: from 0º to 70ºC
Reasons to start using an espresso refractometer in your coffee lab
To know the quality of a coffee, you have to try it! If the coffee is not balanced, you can adjust various factors such as grind, temperature, pressure, water flow... and thus improve extraction and flavor.
The flavor depends largely on how many properties you have dissolved from your ground coffee. If you dissolve too little, your coffee will be acidic, salty and astringent or "under-extracted." And if you dissolve too much, the coffee will be bitter and have wood and charcoal or "over-extracted" flavors.
The espresso refractometer measures the amount of dissolved solid particles in your coffee, in a scientific way. What is usually called the TDS or Total Dissolved Solids or Total Dissolved Solids in a liquid, and knowing this result you can calculate - by means of some simple formulas - how much percentage of the ground coffee you have dissolved ... or what the flavor will "theoretically" be.
5 Reasons to start using an espresso refractometer in your coffee lab
- Professional baristas who want to measure the consistency of the extraction.
- Coffee shop owners who want to control the quality of coffee scientifically.
- Manufacturers of machines to control the constancy of the machinery.
- Coffee roasters who want to control the quality of the roast profile.
- Trainers who want tools to better explain Espresso DNA.
Conclusion
Is a coffee refractometer something you need? Well, no. But if you have a knack for budget planning and science, using a coffee refractometer is a cool way to know more about coffee and how to make delicious brews consistently.
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