My History with TDS

I wasn’t sure Total Dissolves Solids (TDS) would correlate to taste. It was a good metric for sure, but I wasn’t sold on the cost. I published a work on the Staccato Espresso shot, and the main critique was that I didn’t use TDS as has been the standard in the barista world. Instead, I use a scorecard of 7 metrics (Sharp, Rich, Syrup, Sweet, Sour, Bitter, and Aftertaste) resulting in a final score. These scores were subjective of course, but they were calibrated to my tastes and helped me improve my shots.

Eventually, I caved, and I bought a cheap Brix refractometer. I had a lot of fun examining the TDS over the time of the shot, but of course, some weren’t convinced because it was done by eye-sight. So I decided I would get a $100 refractometer until I read the reviews were bad, and as chance would have it, I found someone selling an Atago for $200. Normally, an Atago would cost $300 or more, and an Atago can be difficult to find in the USA.

To convert Brix to TDS is done using a simple formula:

TDS = 0.85 * Brix

Some have argued that this metric is too simple, and this question would be resolved in comparing Brix to Atago as I have below.

Atago Tests

First, I wanted to test how well the Atago handled changes in temperature as the shot cooled. I pulled a shot from my trusty old Odea Giro Superautomatic because I wasn’t concerned about a high TDS shot.

I also wanted to test filtering the sample before measuring TDS. Some have claimed you should filter samples before measuring TDS, but a study showed concluded that the filters lowered TDS. They did find that filtered samples have less variability in measurement. I also wanted to do what scientist do and see if I could quickly verify their results without buying expensive VST syringe filters. To test filtration, I used an Aeropress paper filter.

Here was my setup: