Cupping TDS and Ext % change over time ? ?

We often host classes here at Torch.

One of the many classes we host is the Q Grader course. One of the goals of the Q course is to calibrate cuppers to a sensory standard, so when anyone in the industry talks about coffee quality we have a standard to base our decisions off of.

I also noticed throughout the 10 Q courses I have gotten to help with that many people have pre-conceived notions about how to break, clean, and pour water. 

This got me thinking, do these variables really effect TDS and extraction that much? If they do, then the Q course also needs to calibrate on breaking, cleaning, and pouring methods as well.

So I took to the cupping lab and VST refractometer to do some research.

Check out my results Below.

*Note, each experiment was done with the same coffee on the same day, at the same time. However, the coffee for each experiment was different.

So TDS results should be compared to other tests of the same type, not across. I used 11 grams of coffee and filled each cup to the top, which is 200g of water.

Extraction % = (TDS  x Beverage Weight) / Dose

In cupping, dose and beverage weight are the same, so extraction is based on TDS. I didn’t do extraction calculations, but by the nature of the formula and cupping, extraction increases as TDS increases.

One Question I am answering:

• Do pouring methods, breaking methods, or cleaning methods effect TDS and extraction percentage?

If so, then we need to be more careful about our pouring order, breaking order, etc and calibrate.

Four different tests, each broken down into different experiments

• Each experiment TDS will be taken every 30 seconds until 12 minutes

  • Break time

    • Will be broken at the following times and then immediately cleaned.

    • Break method will be push x2 then stir

      • 3:00

      • 4:00

      • 5:00

    • Break at 6:00

  • Cleaning Times

    • Break method will be push x2 then stir at 4:00

    • Will be cleaned at the following times

      • immediately cleaned.

      • +2 minutes

      • + 5 minutes

  • Break Turbulence

    • Break at 4:00

    • Differing breaking methods

      • Stir x1

      • Stir x3

      • stir x7

      • Push X 2, then Stir

      • Push X 7

  • Pouring turbulence

    1. Bunch of spins

    2. One steady place- low 

    3. One steady place- high

    4. Break at 4:00

    5. Use Push x 2 then stir

    6. Then test TDS every 30 seconds

       Notes*

    7. The “high” cups had the most bubbles on top and the lowest TDS

    8. Low and spins were very similar TDS

    9. Cup 1 of the “low” I accidentally splashed some of the coffee out of the cup, so the TDS readings were all low. 

Conclusion

• Similar to what I have witnessed in French press brewing, the TDS of full immersion methods plateaus at a certain point and very slowly increases after that. With cupping, it is the same.

• Breaking methods do not seem to matter, as long as all of the coffee grounds stay in the cup.

• Breaking time seems to only have an effect for the first few minutes, then the TDS evens out.

• Cleaning times do not seem to have an effect.

• Pouring high produced lower TDS and extraction. I believe this is due to the formation of air bubbles that effected extraction. Pouring in circles didn’t seem to matter. Conceivably due to the grounds then immersing for 4 minutes before breaking.

Cupping TDS Forms

How to experiment？

With so many coffee courses being offered both on and offline, many people are starting to blindly regurgitate what others say.

The specialty coffee industry was started by people that challenged the traditional standard of what coffee was and how it was served.

Let us never stray from that.

To promote a more sustainable coffee chain, we need all of the links to be strong. This requires the baristas, brewers, roasters to continually experiment, push the boundaries, and master their craft.

So in this article I want to talk about doing experiments, and give you 2 examples of an experiment I recently did.

As many of you may have learned in middle school science class, there is something called the “scientific method.”

It is as follows: observation, question, research, hypothesis, experiment, analysis, conclusion.

Observation:

Many brewers have different methods of the bloom, yet they all swear their way is the best.

Stir? Pour slowly? Pour fast? Which ratio is best? Or a 1:2 or even a 1:3?

Question:

What would the effect of changing the bloom temperature and ratio be?

How does changing bloom temperature or ratio affect the overall cup?

Hypothesis:

If I use a lower temperature bloom, then the acidity will be lower.

If I use a higher ratio bloom, then the acidity will be brighter.

Experiment:

It is important to know how to isolate variables. If you change too many variables, you will be shooting in the dark. You won’t know the difference between coincidence, correlation or causation. For example, when I look at one variable, I keep ALL of the other variables constant: dose, ratio, temperature, height, spins, time, etc.

With science, the more objective the better. However, in coffee, TDS and extraction numbers don’t necessarily mean the coffee is delicious. So I will be using TDS, extraction percent, and sensory analysis to compare and contrast the cups.

In any experiment, you need to have all of the variables written down. Be clear which variables you are changing, and which variables you are not changing.

Make sure to write EVERYTHING down: the more information you write down, the better. This will help with analysis, repeatability, and accuracy.

Experiment 1.

In my first experiment I altered the bloom temperature, but kept all other variables the same:

Bloom time, brew temp, dose, ratio, time, grind size.

For this experiment I invited Q grader instructor Marty Pollack, and Sudanese Q Grader Ahmed Tahmer to taste with me and see.

The coffee for this experiment was Torch’s Myanmar Wa State, washed processed coffee. This coffee is a very balanced cup of coffee. It has comfortable acidity, medium sweetness, smooth body, and a clean finish.

Experiment 2.

This experiment was to see how bloom ratio affects the overall cup. I altered the bloom ratio, but kept all other variables the same:

Bloom time, temp, dose, brew ratio, time, grind size.

For this experiment I invited Q grader instructor Marty Pollack to taste with me and see.

The coffee for this experiment was Torch’s Yunnan Zebra Manor Natural processed coffee.

This coffee is a crazy fermented natural. Comfortable acidity, intense sweetness, thick and smooth body, with interesting flavor notes.

Analysis:

At this stage, you just point out trends. Try to get all of the trends out and on paper. This will help you draw conclusions. It is important to not talk about “why” just yet. Just clearly point out “what happened.”

After you identify all of the trends, then take a step back and ask “is there a trend among the trends? Is this trend supported by background research? Why would this be the case?”

My analysis:

Changing the bloom for the clever dripper does not have much impact.

For the v60, the bloom had more of an impact. The TDS and extraction changed, the acidity and balance of the cup were different.

Extracting more out in the beginning, i.e., higher bloom temp and bigger ratio, led to more acidic cups of coffee. Anecdotally, cold brew has low acidity. I have talked with several people that brew cold brew, and they use low temperature water at a long time. The higher temperature led to more harsh acidic tones.

Conclusion:

Combining your background research, experiment and analysis, what can be learned?

My conclusion:

There are not any hard and fast conclusions that can be drawn. If I wanted to be able to make some hard lines that would be true across several coffees and different brew methods, I would have to repeatedly brew the same coffee over and over to get accurate results. Then I would have to brew with several coffees of different origins, densities, varietals, processing methods, roast dates, etc.

However, what I noticed about increasing extraction in the beginning goes with the background research I have done: acids dissolve quicker, but require higher temperature. This is why cold brew made with low temperature is lacking in acidity.

Under-extracted coffee also has a very harsh acidity with an ‘empty’ aftertaste as the sugars have not dissolved fully into the cup yet.

I never want to blindly follow anyone. I want to know why things are the way that they are. Even if someone else has done an experiment and can objectively prove an answer, it is still important to do it yourself. You can know something to be true because someone else said it, or you can know it to be true because you yourself have experienced it.

Experience leads to wisdom.

Future development:

In my opinion this is an important step that is not always highlighted. Sometimes in your quest for an answer, you stumble upon a lot more things that you are curious about. You don’t want to constantly chase rabbit trails, but you need to identify these other questions, so you can put time aside later to find the answers.

This is an important step in creating a feedback loop: what went well, what would you change, what other questions do you have?

My Future Development:

Does the quality of coffee matter? Both coffees I used are 84+ coffees. If I were to use 78-82 coffees, how would the extraction be changed?

In my second experiment I used a grinder that I am not use to using and my brews were all under extracted. Using a grinder I am comfortable with would have led to good extraction. Would a different extraction highlight different aspects of the cup that have been changed?

Maybe.

The world is a beautiful and complex place. We will never know everything, but it is fun to work and uncover some of the mysteries along the way.

The more I learn, the more I realize that I don’t know very much. This practice of being constantly humbled by the complexity of nature is both frustrating and exciting.

Keep on.

Push the boundaries. Master your craft. Honor the work of the farmers.