Minimum contact time for optimal espresso extraction

Today I was served an EK espresso with a shot time of 13 seconds. I decided not to have any preconceived ideas of what it might be like and just go into it with an open mind. I did not hate it, but neither did I enjoy it. I was wondering what scientific knowledge can be provided on this topic in regards to minimum contact time for optimal extraction. Surface wetting and diffusion are heavily time dependant so I’m told… I’m also well aware there are many variables that come into play here i.e. origin, density, solubility, grind size, temperature, brew formula et cetera but I would like to hear some non bias opinions on what can/cannot be achieved, in such a short brew time. Thank you

First of all, EK isn’t a good choice for making espresso but we still can use it with a correct setting. Secondly, 13 seconds sounds really short i guess the main problem is still the grinder’s setting.

I’m not sure if you read my post properly but I am actually looking for scientific evidence and non biased opinion. If you can contribute please do…

The EK creates a higher percentage of fines than most (if not all) espresso grinders. So you can pack more coffee into the same space, while also allowing faster extraction due to the greater surface area exposed. Yes, diffusional equilibrium is time dependent, but the greater amount of fines negates the need for a longer contact time. Brew temperature is probably the most important aspect to a short shot time, along with the pump pressure as well. A shorter time means you’d need a higher brew temp to allow for an optimum extraction, and pump pressure would play a part in how much time the water has in contact with the water, even in a short shot time.


Hello @JonoNiclair
I would like to share my personal understanding on what would have happened in the espresso extraction served for you; Ek 43 is a grinder that gives more even grind particles, which means it creates less fines when comparing to the usual espresso grinders. All espresso grinders produce a bimodal particle distribution that means a typical dose will have two major grind size particles.There will be fines, which are typically below 100 microns, but in a larger proportion by percentage volume, there’ll also be particles in the 200-1000 micron range, the fines from the normal espresso grinders will form a compact cake and higher resistance in the portafilter and slower flow rate of the espresso. But in the Ek43 grinder, it creates lesser fines and also more even grind size particles they create a less resistance in the portafilter resulting in a faster flow rate of espresso (like the one you got 13 seconds espresso).

Now coming back to your question In shorter brew time the water can dissolve only components that are small in molecular size and has high solubility, which is Chlorogenic acids. So your espresso was technically under-extracted. If I understood correctly, your espresso would have tasted light body, acidic, ashy and woody.

If you have any other opinions, please share.

I’m really interested in this one.

Fairly convinced we can grind finer than we have been, but this mucks up flow and evenness.

If we can figure out how to grind finer and keep shot times low it’ll be glorious!

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