Experiment Review - What is the Connection Between Brew Temp and TDS / EY %?

Join us for an afternoon of reviewing our findings!

SEASON FIVE, EPISODE TEN

Experiment Review - What is the Connection Between Brew Temp and TDS / EY %?

Today we will look at an experiment that we conducted in order to answer a question we had. The initial question that we had was “do lower brew temps equal lower TDS values?”

This can be a larger conversation of how brew temps affect TDS at all. We are simply looking to answer a question, perhaps not as an ultimate scientific answer. But at least as a direction for us to think in. 

We will look at our hypothesis, findings, and land on some conclusions for today’s findings.

Our hypothesis is this: higher brewing temps can and will result in higher TDS values and EY values respectively. 

To measure this, we decided to brew a minimum of six brews. Ranging from 100 C downwards to 70 C going down 5 C between each brew. 

Meaning we had brew temps (all in Celsius) that were

• 100

• 95

• 90

• 85

• 80

• 75

• 70

In order to keep things as consistent as possible, the only variable that was changed was brew temp. 

Our constant variables were:

• Grind size // 9 on EK43

• V60 dripper // ceramic

• Stagg Variable Temp Kettle

• Acai Peal Scale

• 18g of coffee: 280g of water // 1:15.55 ratio

• Counterclockwise pours

• Pouring intervals of: 

  • 00:00 - 50g in 10sec pour 

  • 00:30 - 280g in 45sec pour

• Coffee used: Honey Processed Ethiopia (SEY roasters // Dumerso) 

Let’s look at what we experienced as we tasted each brew.

100 C Brew:

This one had clear sweetness, it was sharp and defined in taste and body.

95 C Brew:

This was immediately softer, with a creamier mouthful and overall delicate nature.

90 C Brew:

This brew was highly aromatic and had a rich herbaceous-ness to it. However, the flavor lacked complexity and was very one-note in taste.

85 C Brew:

Very green in smell but very sweet in taste. Honey-like floral sweetness.

80 C Brew:

Clearly under-extracted. Sour on the palate but has a soft texture.

75 C Brew:

Increased sourness but sweetness increased too.

70 C Brew:

No depth in flavor or aroma. However, it seems that sourness has been quite diminished.

—

These were just what we tasted. But what about the question that started this whole experiment? 

What was happening to the TDS and EY percentages? 

Our hypothesis proved to be mostly true. The highest brew temp resulted in a TDS of 1.44% and an EY percentage of 19.36%. Whereas the lowest temp brew clocked in a TDS of 1.20% and an EY percentage of 16.53%.

We did have a thought mid-way through our trials. We sort of expected that the overall brew times would increase as brewing temperature decreased, furthermore causing these slowed-down brews to give us higher extraction readings. This proved to be correct in our 80 C test where the TDS/EY values were 1.31%/17.39% at a 04:30 brew time. The previous value (which was brewed 5 degrees hotter) had a TDS/EY of 1.22%/16.67, with a brew time of 04:19.

Other observations in bullet points

• As temperatures lowered, the mid-slurry slowed substantially.

• Blooms behaved really weird the lower the temperature was.

• Thinking lower brew temps could benefit from longer, and maybe heavy agitated blooms 

• Lower brew temps gave way to particles sticking more directly to the filter. Slurry became far opaquer as temps dropped.

PLEASE CLICK HERE FOR FULL DATA

Conclusion
We set out to see if we could see a trend in TDS values as we reduced our brewing temp, and we did just that. This certainly could benefit from further experimentation, and it is even likely to be variable depending on the coffee used.

Nonetheless, we feel confident based on these findings that yes, higher brew temps will generally yield higher TDS and EY % values. 

Clearly, there are other ways to tighter control this sort of experiment, resulting in findings being more concrete and scientific. However, we are searching for simple, replicable answers, similar to the variables of a home barista. 

Let us know what your experiences are in regard to extraction and water temperatures. If you like what we do, please support us on Patreon.

Until next time!