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#136

Levy Tamp vs Pergtamp

Tamping is one of the crucial steps to espresso preparation. Last week, we set out to test two different aspects of tamping; the levelness of a tamp, the tamper's base size and their effects on the resulting espresso. If you haven't already read it, you can check it out below! This time, we are doing a direct comparison between the Levy Tamp and the Pergtamp.
Tamping is one of the crucial steps to espresso preparation. Last week, we set out to test two different aspects of tamping; the levelness of a tamp, the tamper's base size and their effects on the resulting espresso. If you haven't already read it, you can check it out here! http://compoundcoffee.com/experiments/10_the-most-important-article-about-tamping-you-will-ever-read
This time, we are doing a direct comparison between the Levy Tamp and the Pergtamp.


If you are unfamiliar with the workings of expresso extraction percentages and the use of the coffee refractometer, you can always read our previous article over here : http://compoundcoffee.com/experiments/9_King-of-Distribution-Techniques to get a quick overview and understanding of espresso extraction percentages.

Now let's dive straight into the 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.

Coffee 

Ethiopia, Sidamo Guji
Process : Sundried Naturals
Variety: Ethiopian Heirloom
Roast Age: 10 days from roast date 
Agtron : 70 (Whole Bean), 90(Ground)

Equipment

Grinder : Nuova Simonelli Mythos One Climapro Grinder
Distribution Technique : Stockfleth Method
Tamper : (Controlled Variable) / Initial Calibration with Levy Tamp 58.5mm diameter
Portafilter Basket : VST 20g
Espresso Machine : Slayer V3
Coffee Refractometer : VST Coffee III
Calibration : 20g Dose, 40g Yield, Shot : 12s Pre-infusion slow ramp to 3 bar, 16s 9 bar full pressure, Total brew time: 27s
                   Water temperature : 92.3°C. Final EY 17.75% (La Marzocco Stock Tamper).
Dose Tolerance : 20g ± 0.1g
Shot Tolerance : 40.0g ±  0.5g

Null Hypothesis 1:

Since the tamper bases are the same size, the pergtamp should not extract more than the levy tamp.

Methodology :

To see what the Pergtamp and Levy Tamp look like, you can refer to our previous post here : http://compoundcoffee.com/experiments/10_the-most-important-article-about-tamping-you-will-ever-read

(Steps)
1. Calibrate with the Levy Tamp.
2. Pull 10 espresso shots using the calibrated settings using the Levy Tamp.
3. Calibrate with the Pergtamp.
4. Pull 10 espresso shots using the calibrated settings using the Pergtamp.
5. Wait for espresso shots to cool to room temperature.
6. Measure Total Dissolved Solids (TDS%) and Extraction % for each sample.

Results:

Levy TampPergtamp
YieldTDS%EY%YieldTDS%EY%
39.7g9.32%19.10%40.0g9.4%19.40%
40.1g9.3%19.25%39.7g9.1%18.66%
39.9g9.13%18.81%39.5g9.37%19.11%
40.4g9.03%18.84%40.0g9.13%18.86%
40.1g9.05%18.75%40.0g9.08%18.76%
39.8g8.98%18.47%39.7g9.44%19.34%
39.9g8.98%18.52%40.0g9.27%19.14%
40.0g9.15%18.90%40.2g9.36%19.41%
40.1g9.06%18.77%40.2g9.27%19.23%
40.4g9.12%19.02%40.1g9.25%19.15%
Average EY%18.84%19.11%
Standard Deviation0.78%0.75%
Variance0.2420524%0.264561%
Range0.058589382%0.069992309%
P-Value10.031842821


Conclusion:

In our previous experiment, we pitted 3 tampers against each other along with 1 of the tampers being crooked. We found that the larger diameter bases provided a significantly higher extraction and tastier espresso. Although the crooked tamper did not have diminished extractions, it did taste significantly worse than a level tamp with the same tamper, showing extra bitterness and astringency.

This time, we pitted the two larger diameter bases against each other. Based on the final calculated P-Value, since the value is less than 0.05, we can safely reject the null hypothesis and say that there is a significant difference in extraction between the Levy Tamp and the Pergtamp, with the latter achieving higher extraction percentages. Howeve, we wish to add that althought the Pergtamp does give higher extractions, the espresso shots have tasted slightly less clean than the shots from the Levy Tamp. Shots pulled with the Pergtamp have shown hints of over extraction, with some bitterness and slight astringency appearing in the finish of the espresso. Grinding coarser did not fix the problem as the resulting underextraction only compounded on the issues. Therefore, although the Pergtamp has shown to achieve higher extractions, we have switched to using the Levy Tamp over at our roastery instead due to its ability to provide us with cleaner tasting espresso shots.

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