What is the TDS in coffee? how to measure the concentration of coffee? how much is espresso?

It's hard to taste coffee, but one thing people always taste is the strength of coffee. We can all agree that espresso is stronger and therefore more flavored than filtered coffee. But let's take a closer look at the power of coffee again!

How do we measure strength?

Just saying that something is strong is not scientific or accurate. We need to measure power so that we can talk about the same thing. In coffee, strength is measured in the form of total dissolved solids (TDS), usually as a percentage (%). When we measure TDS, we are evaluating the concentration of soluble matter so that the soluble matter in coffee can be condensed to the amount in the cup. In short, the concentration of coffee (strong) or the water quality (mild).

It is almost impossible to look at the TDS of the drink alone, so a refractometer is needed to measure it. The refractometer can measure the refraction angle of light in the liquid, thus distinguishing the thickness of the liquid. The refractometer is usually used in the laboratory to test plasma proteins in the blood or to identify substances in gems. Coffee is also easy to use! To measure the TDS of coffee using a refractometer, follow these steps:

1. Reset the refractometer to zero with distilled water (not needed before each reading, only once a day)

two。 Stir the drink well (the coffee is delaminated very quickly)

3. Sampling pipette

4. The pipette pours the coffee on the refractometer glass so that the coffee covers the glass.

5. Wait 10-20 seconds.

6. Close the cover of the refractometer and press "GO" until you see the same reading three times in a row.

7. Dry the glass with a paper towel

8. Wipe the glass with an alcohol pad or wipe the paper towel with alcohol

Be careful! This process works if you want to measure filtered coffee. When measuring with espresso, you need to filter the sample using a specific filter (such as this) to remove carbon dioxide from the sample. Then, take the sample from the espresso with a syringe, insert the filter into the syringe, and push the sample through the filter. Otherwise, the steps for TDS measurement are the same.

How to use TDS?

One way to use TDS is to define different coffee drinks. Espresso is espresso when its TDS is between 8-12%. Have you ever heard of ristretto? There are millions of definitions of how to make ristretto, but I think the most accurate way to define it is to say that the TDS of ristretto should be more than 12%. So it's just a stronger espresso (maybe not enough? ). If you work LUNGO in the same way, its TDS should be between 2-8%. For filtered coffee, the correct TDS should be between 1.1% and 1.35% (SCA Golden Cup Award), but I think this is quite mild for light roasting, so I would like to raise it to 1.9%.