# Does coffee stop ‘extracting’ at any point ?



## NickDa (Dec 14, 2019)

I know this sounds weird and counter to logic ( especially since cold brews have to steep for hours on end ) but I am asking because recently I saw a french press video ( I'm pretty sure it was James Hoffman's you tube video ) and the person basically said that after pouring water and letting it steep for 4 mins ( might have the number wrong ) to basically break the crust and this will stop the extraction . Does this sound right or I have misunderstood?

Also for reference looking at the french press recipe in the coffee atlas ( James Hoffman ) and has the following text right after the recipe :

Many people recommend pouring out the entire pot once the brew is done to prevent the grounds continuing to steep and over extract . If you follow the instructions above the coffee should not continue to brew or add negative flavours, so this is no necessary.

To me that sounds like the coffee stops extracting .


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## MWJB (Feb 28, 2012)

Yes, extraction plateaus in a steep, based on thermal retention...the faster it cools (open cup, single walled glass press, Aeropress, Clever Dripper) the lower the terminal extraction...the hotter you can keep it (insulated brewer, or some way of maintaining a high slurry temp like siphon) the higher the terminal extraction.

If you wanted to get the highest extraction, there's no point breaking the crust early (you would only do this as part of a cupping/diagnostic protocol), it likely drops the slurry temp & clamps what is possible extraction-wise.

French press & immersion brews are very hard to over-extract, as espresso can be too with lighter beans. Drip is the most 'brute force' extraction.

Generally speaking, only about 25-35% of a bean (depending on origin) is soluble material, so even if you brew drip at a long brew ratio, gains after a point are minimal, as you are diluting faster than you are extracting. Rate of extraction tails off exponentially as the brew progresses, early extraction is fast, late extraction is slow.

Cold brew can be left for hours because cold water is a very bad solvent, almost all cold brew is under-extracted compared to hot brew/espresso. Grinding the coarse end of espresso and leaving a cold brew at a normal brew ratio for hot coffee, takes 2-3days to get into the normal immersion zone.

In my brewing with glass French press & smaller immersions, extraction seems to level out around 22% +/-2% using the immersion formula...this takes 20-40mins depending on grind & brew size. Using an insulated steel press and steeping for an hour, or more you can bump this up by 2% (and you don't need to worry about cool cups of coffee).

There is no need to remove the brew from the slurry after a few minutes, unless you are aiming for a low extraction (which is perfectly reasonable if you want a quick immersion brew - I do this with half my Clever brews, updose to 85g/L, grind coarse & steep for 60sec.). There is a point between very low extraction and the normal range/big hump, that produces awful, flat & bitter cups. But, this is not over-extraction, it's just a dead spot & extracting more can often improve things.

Coffee in a steep, does stop extracting, but usually it's because we stop it, rather than there is nothing left to extract.


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## NickDa (Dec 14, 2019)

wow, so much good information @MWJB , really appreciate it!

Thanks a lot

N


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## the_partisan (Feb 29, 2016)

I would say after 10-15 minutes, you're really hitting diminishing returns in terms of extraction, as MWJB pointed out - also there's no rule saying to break the crust at 4min instead of say 10min or 15min - if you let it stay long enough it will sink by itself anyway and you can just remove the foam with a spoon, if any is left by that time. It's just something cuppers do to keep things consistent between the different cups they're tasting.


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## Rob1 (Apr 9, 2015)

I let my Sowden brew for about 40 minutes, sometimes a bit longer. I don't know when extraction stops but I do know there's a huge difference in taste between 5 minutes and 40.


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## MWJB (Feb 28, 2012)

As far as percolation goes, after a point you start diluting faster than you can extract, so unless you make massive grind changes brew to brew, extraction will tail off & effectively plateau. Here are some espresso brews made at similar (not the same) grind settings, Scroll down to the chart & you can see that 1:1 extractions here are low, getting into the normal range around 1:2, after 1:3 extraction doesn't rise at the same rate as between 1:1 to 1:3 & the drink really just get weaker.

This isn't offered as any kind of 'science', I could likely have extracted more at the longer brew ratios by grinding finer, it's more an example of how things develop at a given/similar grind, in more 'day to day' scenario...

https://docs.google.com/spreadsheets/d/1P_nLGSU-2BmDUr3qoeiaEQp4IddN0-rv6Gpj5ZDYP7U/edit?usp=sharing


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