Crust in Aeropress - Page 3

Coffee preparation techniques besides espresso like pourover.
jpender

#21: Post by jpender »

DanN wrote:I have also heard that breaking the crust in full immersion causes the grounds to " fall out of suspension " and drastically reduce extraction. But why does it reduce extraction. Wonder what the science behind that is . Just because it falls to the bottom why would that impede with extraction.
I've always thought that people break the crust so that the grounds are out of the way for tasting, not to stop the extraction.

I'd like to see the comparison in %TDS after 20 minutes between cups where the crust is broken at 4 minutes and cups where it is left to float until it sinks on it's own. Extraction tapers off drastically even without breaking the crust. How much of a difference does it really make?

DanN

#22: Post by DanN »

I don't have a tds reader to confirm but JJ Bean coffee roasters in Canada claim NOT to stir or touch the crust for best results. I was a skeptic and I used to stir the heck out of my French press but not anymore. I think the gentle slow pour from a height is itself an agitation in itself and nothing additional is needed. I tried a sample experiment where I added water to the brew bed in a French press using a shower head which drips water very very gently. That coffee lacked lustre. Tasted just bland. So controlled agitation seems to be the key. Also in another experiment I poured boiling water from a feet high and that coffee kinda jumped out in acidity...

Turbulence is a double edged sword and if used correctly can provide spectacular results I guess....

https://jjbeancoffee.com/pages/brew-guide

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atao

#23: Post by atao »

I have used this old Stumptown inverted aeropress technique for years and have found it to be incredibly consistent at delivering good brewed coffee.
Usually the thing i adjust for light vs. dark roasts is temperature and grind a little but not the recipe.

It does involve a short stir at the beginning of brewing and some rotations at the end of brewing to agitate a little.
I think these both address the question of what to do with crust.

https://web.archive.org/web/20150412190 ... aeropress/

jpender

#24: Post by jpender »

DanN wrote:I don't have a tds reader to confirm but JJ Bean coffee roasters in Canada claim NOT to stir or touch the crust for best results. I was a skeptic and I used to stir the heck out of my French press but not anymore. I think the gentle slow pour from a height is itself an agitation in itself and nothing additional is needed. I tried a sample experiment where I added water to the brew bed in a French press using a shower head which drips water very very gently. That coffee lacked lustre. Tasted just bland. So controlled agitation seems to be the key. Also in another experiment I poured boiling water from a feet high and that coffee kinda jumped out in acidity...
It would be interesting to see the data from those "innumerable" tests that JJ Bean Coffee Roasters says they did. Without that it's just another story. Stir, don't stir, spin, whatever.

I did some long steeps in an insulated vessel a while back, up to 40 minutes in length. Instead of pouring onto the grounds I added the grounds to the water and gently folded them in. I used to do French press and Aeropress that way so that I could better control the water temperature. When you pour into a cold vessel what brew temperature do you end up with? It depends. But if you start off with a full vessel of water and wait for it to cool to a given temperature then I think it's more consistent.

With a long enough steep the grounds fall on their own. You don't have to break the crust because there isn't one. There's really no need to filter either, just decant. To avoid disturbing the brews I didn't sample them until the end. So I did parallel brews and terminated them at different times in order to get a pseudo-sequence of the extraction curve. For what it's worth:


jpender

#25: Post by jpender »

There was a paper published in Nature earlier this year that investigated the equilibrium strength and extraction of immersion brewed coffee. They found that, except for very low coffee:water ratios, the equilibrium or maximum extraction was reached within 20 minutes. They did not stir.

My own brief experiments suggest that it does continue. But I used an insulated, partially lidded vessel so that the temperature never fell below 190°F, even after 40 minutes. The authors of that paper used open containers without any insulation and had final brew temperatures of 140-160°F after half that time. Perhaps this is an important difference. Or maybe my limited measurements are misleading.

DanN

#26: Post by DanN »

Thanks for sharing your results John ....so looks like as long as the water is hot enough, extractions do continue in an insulated space. So looks like we need to know when to stop and decant ...as too much extraction ain't always good right...

DamianWarS
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#27: Post by DamianWarS »

DanN wrote:I don't have a tds reader to confirm but JJ Bean coffee roasters in Canada claim NOT to stir or touch the crust for best results. I was a skeptic and I used to stir the heck out of my French press but not anymore. I think the gentle slow pour from a height is itself an agitation in itself and nothing additional is needed. I tried a sample experiment where I added water to the brew bed in a French press using a shower head which drips water very very gently. That coffee lacked lustre. Tasted just bland. So controlled agitation seems to be the key. Also in another experiment I poured boiling water from a feet high and that coffee kinda jumped out in acidity...

Turbulence is a double edged sword and if used correctly can provide spectacular results I guess....

https://jjbeancoffee.com/pages/brew-guide
DanN wrote:Thanks for sharing your results John ....so looks like as long as the water is hot enough, extractions do continue in an insulated space. So looks like we need to know when to stop and decant ...as too much extraction ain't always good right...
diffusion doesn't need any external energy it just needs a concentration gradient and it will naturally equalize simply because one side is different from the other. there's an increased probability for the higher concentration to move towards the lower concentration and it will naturally want to balance and that is diffusion in the simplest terms. Like when you drop ink in water it will first appear quite noticeable and then slowly fade until the entire water has a balanced colour. BH has done some study on it and I'll quote their series on immersion, it's behind a paywall and has a mention of their other content so you will have to read with that in mind.
In a static immersion brew such as a French press, where a coffee bed forms at the bottom of the slurry, equilibrium will not be achieved in enough time to serve a customer a 'hot' coffee. Moreover, as we learned in the BH Percolation course lesson on holding coffee, there is no flavour benefit in leaving coffee long enough for equilibrium to be reached. That's because, over time, the hydrolysis of certain flavour compounds begins to make coffee taste noticeably more bitter. We found in our experiment in Lesson 1.08 that the strength (measured as TDS) of the coffee slurry directly above the coffee bed in a French press was 8% higher than the strength of the coffee at the top of the slurry; this fact suggests that equilibrium is a long way off.
in cupping small bowls are used, the crust is broken and then left undisturbed and there is no decanting or filtration, and doing anything like that would disturb the coffee bed too much. I suspect convection speeds the process of diffusion quite a bit as there would be more movement. After the crust is broken and the coffee has settled diffusion does seem to still happen but at a slower rate and with things like cupping that let the coffee bed sit for longer periods the cooling would slow diffusion down more. The graph from jpender, and I've seen similar that show the same results, is that the highest amount of extraction occurs immediately and then fairly quickly has very diminishing returns. BH has done similar tests and has one that measures the TDS after breaking the crust and determined that there continues to be a concentration gradient as mentioned in the quote above and diffusion is still happening enough that they suggest decanting coffee imminently but the top of the coffee slurry seems to be effected a lot slower than the bottom and from 8 to 16 minutes the average TDS at the top goes up by 0.01 where the average closest to the coffee bed goes up 0.0367. Both seem insignificant but the bottom is an increase of 2.5% where the top is less than 0.7% so cupping probably is pretty safe since the bottom is left undisturbed and the surface is the only thing really touched. I leave my french press for about 10 min, at 4-5 min I break the crust then at about 10 min I decant the coffee (I don't press the coffee).
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jpender

#28: Post by jpender »

DamianWarS wrote:BH has done similar tests and has one that measures the TDS after breaking the crust and determined that there continues to be a concentration gradient as mentioned in the quote above and diffusion is still happening enough that they suggest decanting coffee imminently but the top of the coffee slurry seems to be effected a lot slower than the bottom and from 8 to 16 minutes the average TDS at the top goes up by 0.01 where the average closest to the coffee bed goes up 0.0367. Both seem insignificant but the bottom is an increase of 2.5% where the top is less than 0.7% so cupping probably is pretty safe since the bottom is left undisturbed and the surface is the only thing really touched.
So according to BH extraction is not drastically reduced by breaking the crust. Rather there is a stratification of concentration that makes it seem that way in cupping. But it would be different if you collected the entire brew.

In my tests each of the entire brews was decanted and filtered before measuring the strength. Similarly, when I tasted these brews I was not skimming spoonfuls off of the top; I had a full cup taken from the entire brew. None of these, even the 40 minute long ones, were remotely bitter.

DamianWarS
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#29: Post by DamianWarS » replying to jpender »

Of course your method is the most useful as we don't spoon coffee outside of cupping or only consume the top portion. As soon as you decante it any gradient would be equalized which is best for serving. Is this your regular method? I've been doing no press french press before Hoffmann made it a thing but I've never considered leaving it so long the crust breaks itself. A thermal decanter of some sort of course would be needed but it would be an incredibly easy brewing method.

jpender

#30: Post by jpender »

DamianWarS wrote:Is this your regular method? I've been doing no press french press before Hoffmann made it a thing but I've never considered leaving it so long the crust breaks itself. A thermal decanter of some sort of course would be needed but it would be an incredibly easy brewing method.
Someone had posted about doing long infusions, up to an hour, and it seemed so out of the box. He said it brought out sweetness and he didn't mind the wait. So I tried to copy his method, just out of curiosity. I mean, everyone brews for 4-6 minutes, or even as short as a minute or two with an Aeropress. I probably did something different than he did as the longer brews I did were not better tasting to me. The six minute infusions tasted the best, three minutes second best. The longer ones seemed to lose something, at least that's the way I experienced it.

I haven't been doing infusions much lately. I did some while backpacking this summer. But I broke the crust after about four minutes, let it settle for a couple more, and then decanted.

I'd never be happy waiting 40 minutes for coffee, not unless it was amazing. One time I waited in line for about half an hour for an espresso at a Blue Bottle shop. It tasted like hot lemon juice. I couldn't drink it.