We were closed today which gave us a good opportunity to get out the Refractometer and Mojotogo and play around with brew ratios & extraction yields. It's relatively easy to measure but it's the relationship between each parameter that it's the tricky to understand. Thank god for Pip Heath and his scientific mind for leading the way today. It would be awesome if we could close once a week and spend a day just on espresso extraction yields but unfortunately that 'aint going to happen.
I think generally at Dead Man our shots are dosed higher roughly around 21grams, sometimes under sometimes over, and our brew ratios are between 70-75%. Sometimes 75%-80. Other people like it around 65%. Like James Hoffman.
1) Firstly, we started measuring without changing anything around. The brew ratio was 55%. In this instant Pip ran the shot for 30 seconds. We normally hover around 27 secs. We measured and it did taste slightly bitter. As the chart says it was over extracted. 23.1%, Outside the preferred 18-22% range. So it tasted bitter because we ran the shot too long?
| Extraction Yield | 23.1 % |
| TDS | 12.7 % |
| Dose Weight | 20.0 g |
| Beverage Weight | 36.3 g |
2) Then I think we stopped the shot at 25 seconds. It weighed 23.9 grams. Much less than the first. The Brew Ratio was 87 %. And we we under extracted at 16.8% below the desired target of 18%
| Extraction Yield | 16.8 % |
| TDS | 14.6 % |
| Dose Weight | 20.8 g |
| Beverage Weight | 23.9 g
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3) I'm not sure what happen here. Might get Pip to enlighten. I think we changed the grind stayed on 25 secs but totally over extracted the shot.
| Extraction Yield | 28.4 % |
| TDS | 17.4 % |
| Dose Weight | 20.4 g |
| Beverage Weight | 33.3 g |
4) We played around with a few shots in between then decided we like roughly 65 - 68% brew ratio. This shot was overdosed. To weigh we took basket out of portafilter, quickly weighed and put back. I think it ran for 25 secs. (I saved the times in the Mojo but can't work out how to see it from saved recipes)
| Extraction Yield | 23.1 % |
| TDS | 16.1 % |
| Dose Weight | 21.9 g |
| Beverage Weight | 31.4 g |
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5) So we were liking the brew ratio around 65%. If we dosed around 20 grams that would give us 30 grams of brewed coffee. We dosed coffee, quickly took basket out of portafilter, weighed, scooped excess coffee out, exactly 20 grams, quickly placed back in, tamped, into grouphead, brewed for 25 secs. Voila! Extraction Yield of 18.2 %, tasted and yes we liked! A little bright, smooth, balanced and the nutty flavour more noticeable. The numbers look a bit neat but from my understanding we can choose any brew ratio, which is a personal preference and work back from there to ensure correct extraction yields. If your brew ratio is around 70% plus it will be more syrupy, thicker, intense and if say under 65% it will be for what I've a better description, watery, but maybe more balanced.
| Extraction Yield | 18.2 % |
| TDS | 12.1 % |
| Dose Weight | 20.0 g |
| Beverage Weight | 30.0 g |
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6) We then wanted to replicate what we did. This shot ran for 26 secs. We stuck with a 66% brew ratio. So that extra second resulted in a higher TDS in the cup and extracted more coffee from the dose?
| Extraction Yield | 21.2 % |
| TDS | 14.1 % |
| Dose Weight | 20.0 g |
| Beverage Weight | 30.0 g |
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| We are a long way off from totally getting how heads around all this but we now have more definitive parameters to which to articulate to our staff. But more to the point we are determine to make the best coffee we can... purely for our sake but you might as well benefit from it! |
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| The above chart is a diagram of measuring the total dissolved solids of a filter coffee. Taken from the SCAE website on the Gold Cup programme. So in the cup there is 98.5% water and 1.5 % coffee solubles. For espresso it would be 85 - 90% water and 10%-15% coffee solubles.
