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Experiment #155 : Coffee Extraction and Sugar Levels

In many of our experiments, we are always searching for ways to increase coffee extraction without introducing unpleasant bitterness and anstringency. One of the main reasons for this is because higher extractions tend to results in sweeter, more flavourful coffee. Recent research and tests have discovered that full and proper extractions help to result in sweeter tasting coffees. Is this accurate? How does coffee extraction relate to sweetness in the coffee? We aim to find out in this week's experiment.

Disclaimer : We are by no means statistical / math / science experts. This is just a simple experiment carried out to give us an idea of the performance of each method only. People are more than welcome to give their feedback on how we can improve and carry out a more academically approved experiment / report.

Hypothesis 1:

Higher extraction percentages in coffee results in higher levels of sugar in the coffee.


Guatemala Potrero
Process : Fully Washed
Variety: Bourbon & Caturra
Roast Age: 14 days from roast date 
Agtron : 58 (Whole Bean), 70(Ground)


Grinder : Nuova Simonelli Mythos One Climapro Grinder
Distribution Technique : Stockfleth Method
Tamper : PergTamp 58.5mm diameter
Portafilter Basket : VST 18g
Espresso Machine : Slayer V3
Brew Pressure : Full Brew Pressure at 9 Bars / Measured using Scace II
Brew Temperature : (Controlled Variable / Initial calibration at 93C)
Grouphead Flow Rate : 117g water / 10s ( Full Brew Pressure ), 28g water / 10s (Pre-infusion Brew Pressure set to maximum 3 bar)
Coffee Refractometer : VST Coffee III
Calibration : 18g Dose, 42g Yield, Shot : 16s Pre-infusion, 24s 9 bar full pressure, Total brew time: 40s
                   Water temperature : 93.3°C. Final EY 21.2%.
*Optimal Calibration is set at the furthest possible point in extraction whereby minimal to zero astringency or notes of over-extraction is detected in the cup.
Dose Tolerance : 18g ± 0.1g
Shot Tolerance : 42.0g ±  0.5g

Methodology :

1. Calibrate the coffee using 93C water temperature.
2. Pull 5 espresso shots using the calibrated settings.
3. Pull 5 espresso shots at 1:1.5 brew ratio.
4. Pull 5 espresso shots 1:2 brew ratio.
5. Pull 5 espresso shots 1:3 brew ratio.
6. Wait for espresso shots to cool to room temperature.
7. Measure Total Dissolved Solids (TDS%), Extraction % and Brix levels for each sample.

Results :

Average Values41.928.87421.41410.7264.496436.069.93420.62211.954.309241.9212.29619.22614.6163.969653.947.54823.449.194.9572
Value Range0.50.180.590.210.1160.30.420.920.470.18215.120.290.350.310.070.50.3110.350.197


As we can see from the results, the sugar levels are positively correlated with the extraction percentages of the brewed coffee. Since all P-Values across the different brew ratios are statistically significant and less than 0.05, we can conclude that there is enough evidence to support our hypotheses. Higher extraction percentages is positively correlated to higher sugar levels in the coffee. Of course, this is just one of many compounds within coffee and the higher sugar concentration may not offset other undesirable flavours. For example, coffees pulled at 1:3 ratios presented higher levels of sugar in the data but tasted bitter and astringent as opposed to our original calibration. At the end of the day, we still need to taste the final product to determine the optimal calibration of the coffee. The goal of all our research is to be able to increase and improve extraction without introducing the unpleasant elements like bitterness and astringency.

For future experiments we can look at isolating other variables within the brewing process to see if other factors such as temperature or grind size used has an impact on the total dissolved sugar in the resulting brew.

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