Most of us define the quality of coffee according to taste. We drink a cup and decide right then and there whether it is to our liking or not. On the contrary, there are a few individuals who evaluate coffee based on extraction rate. It is measured by a device called the coffee refractometer.
If you are interested in using a coffee refractometer, then you'll enjoy reading the fundamentals that we will cover in this article.
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What is a Coffee Refractometer?
Refractometers typically measure what's known as refractive index. The refractive index is a measure of the speed of light through liquid material. This measurement is useful in a variety of industries, such as manufacturing, agricultural, and medical. For instance, it can be used to determine the sugar content in grapes that will eventually be made into wine. Likewise, a coffee refractometer is used to measure the total dissolved solids in coffee.
Atago PAL-COFFEE (BX / TDS)
What Does the Refractive Index Stand For in Coffee?
The refractive index represents the Total Dissolved Solids (TDS) in a coffee brew. TDS is a factor that's used in computing for the coffee's Extraction Rate - a measure indicating the strength of the brew. Once the TDS is measured, the extraction rate can be established by using the following formula:
What does extraction rate suggest? It simply means that the right quantity of ground coffee, water, time, and temperature will result in a better tasting coffee.
What is the Ideal Coffee Extraction Rate?
While this question can be best answered by personal preference, many coffee connoisseurs would recommend that the most desirable extraction of coffee is at 18-22%.
Under-extracting (less than 18%) can lead to an under-developed taste. On the other hand, over-extracting (more than 22%) can amplify the bitter aspects of the coffee solids.
What to Do Before Using Your Coffee Refractometer
If you've gotten your hands on a brand new coffee refractometer, you're probably excited to try it out immediately. Slow down a bit, pal. Here are some preparatory steps in order to get the most accurate TDS measurements:
1. Calibrate the refractometer
Place distilled or de-ionized water that has been stored at room temperature (20-25 degrees Celsius) on the refractometer' s glass to make it the baseline.
2. Allow coffee sample to cool to room temperature
Stir the coffee sample. After that, transfer it directly into the refractometer sample well. This allows for a more accurate reading.
How to Use a Coffee Refractometer
You are now ready to use your coffee refractometer. Here's what you need to do next:
1. Place the sample on the well
Place a small portion of your coffee sample on the well for 15-30 seconds before taking an initial reading. This allows the sample to acclimatize to the temperature of the well.
2. Press the Start button
Coffee refractometers have an indicator that tells you to press the button for the TDS reading. The results will be automatically displayed on the screen.
MISCO PA203X Palm Abbe
3. Check out the result
The refractometer should bring up a reading of the total amount of dissolved solids (TDS).
4. Use the results to compute for extraction rate
With the TDS identified, you can then use the formula mentioned earlier to calculate the extraction rate. More recent coffee refractometer models can already do the math for you. Simply provide the values for the other variables.
With this information on hand, you can effortlessly make adjustments based on the standards you set for your coffee. This is particularly beneficial to cafes and restaurants that want to ensure a consistent quality across all branches.
How to Maintain Your Coffee Refractometer
Regular cleaning of the coffee refractometer ensures that the device is always at peak performance. Here's what you need to do to make sure that your refractometer performs optimally at all times:
- 1Clean immediately after each sampling.
- 2Make sure that there are no residues present on the surface and sample well.
- 3Use distilled water only, especially on the sensitive parts of your equipment. Tap water contains minerals that will stick to the sides over time.
- 4Thoroughly dry with cloth that has been dampened with a mild cleaning solution.
- 5Do not use harsh cleaning agents and never immerse the device in any liquid.
Where Do I Find the Best Coffee Refractometers?
A coffee refractometer can cost a lot, but it will also take your coffee brewing to the next level. Here's a couple of proven and tested refractometers that are available in the market today:
Milwaukee Instruments MA871 Digital Brix Refractometer
AMTAST AMR300 Digital Coffee Densitometer
The AMTAST Digital Coffee Densitometer boasts a large display with a straightforward user interface. It measures TDS accurately, and it doesn't feel too bulky. On top of that, it has an IP65 rating. This means that you can directly flush the induction tank with water for easy maintenance.
This refractometer can also be used to measure the sweetness of milk tea, fruits, and many others.
These concrete measurements on your coffee brewing will give you peace of mind. For some people, it's satisfying to know that the proportions are consistent for every single brew.
