Espresso Poll: Results and Analysis

October 17th, 2009

First off a big thank you to everyone who contributed to the espresso poll.  It closed out at just under 100 people giving their data.  Out of this some data had to be ignored as it was clearly entered in error, leaving just over 90 espressos worth of information.

I am not a massive statistics expert – and I am grateful to Vince Fedele for taking the data and cleaning it up and doing some analysis on it.

To start with the easy stuff:

Averages:

An interesting average espresso here – I would have suspected a slightly higher dose amongst readers of the blog, but a good number were dosing at around 14g for a double.  The average shot size was good to see.

Average ground coffee weight:  17.2g
Average shot weight:   32.7g
Average shot time: 27s

This shot would have a brew ratio of 53% – for those unfamiliar with brew ratios (credit to Andy Schecter) – Brew ratios. (Old post)

For those of you out there playing the ExtractMojos for espresso, or have been interested in espresso strength and extraction, Vince did a simple calculation where we assumed that extraction was around 20% of the coffee (as people had dialled in for taste) and therefore the likely strength of the average espresso was 12.2%.

This is very interesting to me because the average is pretty much where I have really been enjoying espresso recently.

Reasons behind recipes

I asked people to state why they used the recipes they did.  Here are the results:

preferences

A few surprises for me here:

Not many people use the roaster’s suggested brew recipe.

Flavour was a higher priority than texture.  This is only unusual because we’re talking about brew espresso, whose key pleasure (in my opinion) is texture.

One other reason I wanted people to answer these questions is so I could group them and then analyze.  One big surprise here for me.  I took the top three answers (flavour group, balance group and texture group) and looked at their averages:

Flavour:

Average dose:  17.5g
Average shot weight: 30g
Brew ratio (strength):  66% (13.6% TDS expected) 1

Balance:

Average dose:  18.7g
Average shot weight: 33.4g
Brew ratio (strength):  60% (12.1% TDS expected)

Texture:

Average dose:  16.7g
Average shot weight: 36.9g
Brew ratio (strength):  49% (9.9% TDS expected)

What do the above mean?  First off I was very surprised by the texture group – they pulled the biggest shots, from the least coffee.  Essentially they pulled the weakest shots (from which you’d expect the least texture).  I expected texture focused people to pull shorter shots from more coffee, and yet the results are the opposite.  The flavour group pulled the strongest, thickest shots and the flavour focused people were closer to the average (and how I like my espresso.)

Brew style:

I don’t mind admitting that I will have some preconceptions about how someone will brew espresso based on their starting dose.  Generally I would expect a shorter shot to come from a higher dose.  This has always seemed a little counter intuitive to me, because you have more coffee to extract so surely using less water will only make that more difficult.

I created a simple chart to see if my expectations were correct.  I charted starting dose against brew ratio.  This would mean that if people used more water with more coffee in a linear way then the data would essentially flat line.  This was not the case:

graph smaller

Click to embiggen

As I expected there is an increase in brew ratio (a decrease in relative shot size) with an increased dose.  However you can see the data is all over the place and there is a massive range of shots sizes being pulled from all doses.

From the above graph you can also see the distribution of the doses submitted in the survey.  It may seem strange to see a range from 7g to 24g.  The 7g entries were kept because the shot weight was clearly for a single espresso so didn’t affect the brew ratio calculation.

Summary

There is no right or wrong way to brew espresso.  However, I can’t help but feel this might be one of those moments where the wisdom of crowds has come good.  What I would appreciate is if the average espresso from the group is very different to your own – give it a try!  I’d love to hear your opinions, whether you found anything better from trying to pull a good shot using 17-18g, pulling about 32-34g of water through it (brew on scales) and aim for about 25-28s.  Let me know if you try it!

If I was going to do the survey again I would probably add a few more questions, and I hope to do another survey soon – perhaps about brewed coffee, or maybe espresso again.  Your thoughts welcome.

  1. Again – to clarify:  I couldn’t get people to measure the strength of their extracted shots, so it was assumed that if they tasted good they were extracting approx 20% of the ground coffee into the cup.  Essentially this is something of a guess.  ↩︎

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