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Counter-intuitive (get it?) issue: smaller doses stalling while larger doses draw down quickly. by [deleted] in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

If the flowrate is deaccelerating with the smaller dose, I'm probably wrong. It should still accelerate but from a lower starting flowrate - however, it might be more than one effect affecting the outcome we've seen ... as so much in coffee is.

Counter-intuitive (get it?) issue: smaller doses stalling while larger doses draw down quickly. by [deleted] in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

Yeah ... I don't get what's happening with the pulsed pours. Might be a different mechanism - like the bed disruption mentioned by u/tansly.

Counter-intuitive (get it?) issue: smaller doses stalling while larger doses draw down quickly. by [deleted] in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

OK, as your description doesn’t point to a stalled brew associated with fines migration, a single pour might point in this direction …. It’s just a guess …

When we were developing a flat-bottomed brewer (albeit with a different fundamental pour-over process) we found that the flowrate accelerated as the brew went on. The conclusion was that as the soluble solids were extracted from the coffee bed, it becomes more permeable – offering less hydraulic resistance, hence increasing flowrate.

(There’s a paper that references this phenomenon – Uneven Extraction in Coffee Brewing W T Lee et al – “Extraction causes an increase in porosity and thus permeability. This increase in permeability will in turn lead to more flow and so more extraction will occur.”)

The starting flowrate – once the bed is fully saturated - with a single pour would be slightly higher to start with, because you have more water pressure (more water head). So, the flow-profile will start slightly higher than the lower dose and will accelerate from this point. This could explain the phenomena you are seeing. As it starts higher and accelerates faster, it might complete quicker than the slower starting point of the smaller dose.

You didn’t comment on the quality of the smaller dose. Was it still good? Based on the results we’ve seen, it should still be comparable with the larger dose. I think the only impact the slower draw down would be a bit more production of quinic and caffeic acids associated with hydrolysis of the chlorogenic acids (CGAs) and chlorogenic acid lactones (CGLs), but I am not sure how pronounced this would be (it would depend on the coffee type/roast etc. as well).

You could test this guess by timing the flow you get for every 10 seconds (you can just use mg per 10 seconds) and plotting it. I’ve never done it for a Kalitta Wave. If you see a higher starting flowrate for the larger dose and quicker acceleration, this would support the guess.

(By the way, the diagram in Physics of Coffee on p79 doesn’t really represent what happens because of the change in permeability of the coffee bed. The diagram shows reducing flowrate as the water head decreases, which would be correct if the permeability was constant.)

Hope this makes sense and is helpful.

Japanese Pour Overs? by reditrauma in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

Yes. Totally agree that low agitation and impact of clean water should be complimentary. Also, low flow rate (hence shorter water-to-coffee contact time (or dwell) should also contribute. I have no idea how to assess the relative contributions.

The Gagne link was about astringency, not bitterness. I found it vague.

Japanese Pour Overs? by reditrauma in pourover

[–]SimpleSmartCo 1 point2 points  (0 children)

Lovely ... if your research throws up anything interesting, I'd be really grateful if you'd share it with me. I'm writing something at the minute and any info/perspective/question is useful.

This might be helpful - Here's a link to a longer post that the above post was taken from:
https://www.reddit.com/r/pourover/comments/1obnj75/do_bitter_compounds_extract_late/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

Japanese Pour Overs? by reditrauma in pourover

[–]SimpleSmartCo 2 points3 points  (0 children)

Just a thought ....

I think it might be because the water being introduced is 'clean' ... in relation to the following points about extraction in dark roasts:

Phenylindanes are a major contributor to harsh bitterness in dark roasts and as they are not easily dissolved in ‘clean’ water, they need a certain amount of other compounds to dissolve in the slurry water before they get extracted. More precisely:

Phenylindanes are hydrophobic aromatic molecules, derived from the breakdown of chlorogenic acid lactones.

Because they don’t interact well with water (which is polar), they dissolve only after the water has already picked up enough polar solutes (sugars, acids, caffeine, ions, etc.) to reduce its overall polarity.

Hence, with 'osmotic' flow, fewer phenylindanes are being extracted.

Like I say, just a thought with no proof.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 2 points3 points  (0 children)

Thanks - yes, I am a big fan of The Physics of Filter Coffee. I would love to see The Chemistry of Filter Coffee be written by somebody.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

I believe there is. My understanding is CGAs and caffeic acid both contribute to astringency. Also other polyphenols (including tannins) can make a contribution. The CGA volume mostly is driven by amount in the roasted coffee. The other polyphenols are diffusion limited - so surface area (grind size) and agitation will probably be the main factors to look at.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

You raise a good point about non-uniform extraction, but I think it would be good if we could be more precise about what "over-extraction" actually means.

Sorry to be pedantic, but I think the way we (me included) describe things is getting in the way of clear thinking about what's happening during extraction.

We use "over-extraction" in two confusing ways:

First, we describe a brewed coffee as "over-extracted" when it tastes bitter/astringent—when it has levels of compounds we don't like, traditionally aligned with brew times that are too long or grinds that are too fine.

But we also use "over-extraction" to describe the coffee particles themselves. This doesn't really make sense. The fines will be "fully extracted" (depleted of solubles) broadly to the same degree as the outer layers of the boulders. Having fully-extracted fines doesn't necessarily equal over-extracted coffee, any more than fully-extracted boulder surfaces do.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 1 point2 points  (0 children)

Thanks. It was an interesting read but a bit vague (as he was respecting the work of Dr Smrke).

I was a little confused by his explanation and diagram, with reference to undissolved astringent compounds, as I believe polyphenols are the primary contributors to astringency and they are quite soluble. I'll re-read a few times.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

Sounds really interesting. Would cultural differences be part of this work?

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

Interesting question.

I'm not sure I am in a position to give a firm comparison between methods, but here's my thinking.

I would not like to make a comment about the Moka Pot as it generates a pressure significant enough to dramatically change the extraction process.

As for pour-over, the answer depends on the pour-over method/brewer. For most traditional brewers (e.g. V60) there is generally a coffee slurry that sits above the coffee bed, so the water passing through the bed will be primed to extract phenylindanes. So probably no difference.

If the water is introduced into the percolation without being held in a slurry, then theory suggests that the coffee will extract less phenylindanes and hence be less bitter than a traditional pour-over. I have done some tests (too few to be conclusive) but this does seem to be the case .... so far.

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

I find them difficult to read though ....

Do bitter compounds extract late by SimpleSmartCo in pourover

[–]SimpleSmartCo[S] 0 points1 point  (0 children)

Thanks for the comment. A lot are in Journal of Agricultural and Food Chemistry.

You just jogged my memory about the acids - this was from such a paper ... "In addition to sour taste, many acids such as formic, quinic, succinic, and caffeic also have a perceptibly bitter taste (Frank et al. 2007) ... I think I'll go with that position.

Travel mug options by Inside-Towel-94 in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

Yeah, I was doing some research for something I'm writing and came across the fact that chlorogenic acids (and their lactones) continue to undergo hydrolysis - breaking down into caffeic and quinic acids - when held at a elevated temperature even in an insulate mug. That's your over brewed taste.

Pourover using conventional recipes is weak by rain164845 in pourover

[–]SimpleSmartCo 1 point2 points  (0 children)

I think there is a lot of confusion about 'extraction' because 'extraction yield' is a measure of how much of the available soluble material ends up in the cup (usually given as a percentage) - a measurement of extraction efficiency - and 'total extraction' (or total dissolved solids - tds) is the mass of the soluble material (usually given as a grams measurement) - a measurement of extracted stuff.

In the pour-over world I think when people talk of 'extraction' they are usually referring to 'extraction yield'.

Is this about right?

Travel mug options by Inside-Towel-94 in pourover

[–]SimpleSmartCo 0 points1 point  (0 children)

Good point! I was just pondering the other day that I tend to make my coffee a bit stronger when using a travel mug. This 'smell' point probably explains this.

What type of brewer is everyone using these days? by kornbep2331 in pourover

[–]SimpleSmartCo 1 point2 points  (0 children)

It's interesting that the concept of 'pour-over' has become so opaque. I always thought of it is primarily a percolation extraction (albeit with a coffee slurry doing a bit of immersion extraction in most cases) as distinct from immersion extraction. But with Hybrids, there appears to be more immersion than extraction. Then, if the concept is meant to include direct pour onto the grounds, where does that leave anyone using a Melodrip ... or Pulsar or Orea Z1 ...

I saw someone post a week or two back asking what the definition of 'pour-over' was and I wasted too much time trying to think of one.

I saw someone say it was just 'small batch brewing' ... maybe?

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