hydrophobic coffees vs hydrophilic coffees

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hydrophobic coffees vs hydrophilic coffees

Postby malachi on Fri Jun 24, 2005 7:46 am

i've been theorizing a lot about the implications of the fact that some coffees seem far more hydrophilic than others. i have reached some tentative conclusions.
for example, i'm beginning to think that a bunch of the old school italian techniques that we all scoff at (very light dose, fine grind and no real tamp, etc) may well be the result of blends that are extremely hydrophilic (combined in this case with the use of machines with a very mellow ramp of progressive pre-infusion).
or, as another example, the massive updosing that is done with the Stumptown Hairbender seems to be only possible with a somewhat hydrophobic coffee. this allows for a huge dose without the expansion problems.

so... the question then becomes - what determines the hydrophilic nature of certain coffees? i'm starting to theorize that high grown washed coffees are the least hydrophilic, semi-washed and pulped naturals are more hydrophilic, naturals are very hydrophilic and aged and monsooned are the most hydrophilic.

thoughts?
implications?
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Postby Alistair Durie on Fri Jun 24, 2005 1:02 pm

well the first thing that comes to mind is that roasters have to start being a lot more informative about thier espresso components so that we know what we're working with. breaking down the blend, cupping and pulling origin shots, and knowing when there are changes.

one of my barista's asked me this question the other day: how do washed and unwashed coffees compare in moisture and essential oil, and how does this change the approach for a roaster or barista.

good question.
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Postby xristrettox on Fri Jun 24, 2005 3:26 pm

It's funny that you mention this, Chris. For so long I have been messing with the bender, and that is all I knew. But now as we are constantly playing with single origins/bottomless pf, we are learning a lot about how coffees perform. My inclination is that naturals need to be pulled at lower doses and washed, at higher. Also, the naturals seem to want to sit on the shelf longer. What I mean is that the bender is kinda forgiving even at one day out of the roaster... you try doing that with a natural and it's a real pain. Watching the bottomless pf really reveals what is going on in the brewing chamber.

I don't know about hydro-what-nots, but I gamble that it definately has something to do with how much the coffee has to give in regards to solubles.
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Postby Jimmy Oneschuk on Fri Jun 24, 2005 4:44 pm

during my 'sabbatical' this is something I've had time to investigate more - but mostly based on testing single o's.

and like alistair said, knowing beforehand what I'm working with - so I can have a relative measure of the performance or behaviour I'd expect from a certain coffee. when it comes down to it though - you still need to benchmark your coffee... but for comparison's sake... essential.

of course, I'd love to know pick date, crop growth conditions (hot or cold, precip, etc), farm soil conditions, relative cherry ripeness...

these are all long-term industry things, but perhaps some crafty roaster might capitalize on such an idea.

just my fantasy.
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Postby malachi on Fri Jun 24, 2005 5:42 pm

Hmmm... Billy, you and I need to get together someday soon and pull shots with a whole stack of different coffees.

Yeah... more transparency would be very helpful.
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Postby tonx on Fri Jun 24, 2005 6:20 pm

While I don't have much in the way of answers I will contribute to the muddying of the question.

When you are talking about a blend, the single-origin-shot behavior of any one component might be affected greatly by the differing chemistry of the other components. Behavior in the extraction being more than just the sum of its parts.

Looking at the Illy book, I can scratch together a couple of hypothesis for behaviors of certain coffees/roasts, but I'm no chemist. It seems like some hands on screwing around in a lab environment is where this discussion needs to go. Perhaps if we ever score that second Synesso for the training room...

I think it would be interesting to break out some coffees in the lab, try and classify a small handful of general single-origin behaviors (under similar conditions) and then see how those behaviors transform when mated.

In my limited experience it seems like adding a very small percentage (~5%) of a particular coffee can often have dramatic effects in an espresso blend.
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Postby malachi on Mon Jun 27, 2005 8:03 am

I've been trying to find some or any research on this and have utterly failed.

If anyone knows of where some might be, let me know.

In the meantime, I think I'm going to do some "bathtub chemistry" experiments on my own. I'm planning on simply combining weighed and evenly ground coffees of various types with a consistent weight of 200F water and measuring the expansion of the coffee and noting any observations to start with. I will do this blind, having someone else grind and code the coffee samples, and will do each coffee 3 times.

I hope to test 3 different high-grown washed arabicas, 3 different semi-washed and/or pulped natural arabicas, 3 different natural processed arabicas, 3 different "aged" arabicas and 3 different washed robustas.
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Postby James Hoffmann on Mon Jun 27, 2005 8:41 am

I'd be very surprised if there were any research done on this at all.

If you manage to put down a simple step-by-step that is easily repeatable then you'll probably be able to find people willing to help and pool some results.

I know I can probably get access to a variety of extremely traceable coffees of different natures where I can probably find out quite a lot about exact altitude, growing conditions, picking and ripeness and the like and I'd willing to help.

Would the type of roaster also be key to this - is the porosity (is that even a word?) of coffee key to this as well - I assume it must be if we are looking at weights and the like?
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Postby malachi on Mon Jun 27, 2005 9:11 am

I'm going to start using just coffee from one roaster so I can limit some of the variables (and it happens that there is one I trust 100 meters away - grin).
I'm going to try and limit it to one roast degree and one age out of the roaster as well.

This, of course, is going to limit my coffee options (I won't be able to test aged or monsooned or natural or robusta to start).

What would be cool would be if other people could do the same and we could pool this.

I'm no scientist, and I'm sure there are flaws in my plan so feel free to advise me...

Step by step proposal:

1) boil water
2) grind coffee (hmmm... gonna have to figure out how to calibrate this. i'm going to grind as for espresso, but that's a very fuzzy concept to communicate)
3) weigh out 5 grams (?) of ground coffee
4) put coffee into lined beaker and note volume
5) add 0.5oz (?) 200F water
6) start timer
7) note volume every 5 (?) seconds
8) note time when volume stops increasing
9) note any observations (water unabsorbed, coffee still dry, colour changes, etc)
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Postby tonx on Mon Jun 27, 2005 4:26 pm

water quality is likely to be an issue in your experiment. Some of the behavior you are looking to examine might have more to do with kinetics on a small scale than chemistry on a much smaller scale, which would make grind much more of an issue.
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Postby James Hoffmann on Tue Jun 28, 2005 6:05 am

I think that if this research is aimed at espresso then it should be done with an espresso machine.

There you should have some consistency in brew water - which may be much harder to achieve outside the pf. Plus you are include other things that might induce variation such as pressure.

Please shoot me down on this one - but for me it'd be nice to know the exact weight of the coffee before extraction and then the weight of the puck a set time after 2 fl.oz. have been pressed through - as the more hydrophilic coffees should surely retain more moisture in the puck after. You could weigh the puck exactly 10 seconds after extraction.

I don't know how practical it is to dose and weigh a basket before putting it back into the pf then tamping and brewing then taking the basket out again and weighing it.
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Postby Alistair Durie on Fri Jul 01, 2005 1:00 am

chris, when you say hydrophilic (the attraction to water) relating to ground coffee are you saying that it will absorb more water?

if it is absorbtion, does this cause it to expand more? doesn't expansion correspond almost directly with degassing?

do you think the coffee in your beaker will relate to the coffee in the pf basket under pressure? (change the atmosphere and the results may pivot)

can we think of other methods of testing other than the regular 'ground coffee and hot water'? something simpler with less variables, a method of soaking the coffee and measuring by weight how much water it retains.

a.
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Postby Peter Van de Reep on Sat Jul 02, 2005 4:10 pm

Chris, I am almost certain that no research has previously been done by "scientists" on this topic. Most coffee research I have seen published in peer-reviewed journals is not at the level that it could be at. If you are interested in some of the papers I have found, I can email them to you barring my university account is still valid.

On a more related note, the tentative procedure you have detailed should be alright, but as a few people have said, the water quality will be a factor for sure. Impurities and even the additives that are meant to be in our drinking water will likely cause large variances if the tests were to be replicated somewhere else where water composition could be significantly different.

I would recommend (however picky this may be) that you try to push your weighing of the coffee and measurement of your water volume to a more precise figure. Even 5.0g is better.

Regardless, this is an interesting step to take in the science of coffee, and I wish you luck with it. I would gladly jump on board, but alas, I would find it difficult to get a roaster to join me.

Cheers,
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Postby malachi on Sat Jul 02, 2005 7:02 pm

OK, so I wonder if it would be worthwhile to use distilled water or if that would be too abstracted from the realities of coffee brewing.

I agree that a high degree of accuracy with weight is key.

I am, indeed, talking about absorbtion but absorbtion is one of the specific issues I'm looking at when it comes to espresso. I don't know if there is a direct relationship between age of coffee and absorbtion, whether it represents a significant or minor cause, etc. That's why I think this needs to be evaluated.

I think starting without pressure should give us a baseline to start with. Adding an additional variable at a time seems to make sense to me. Otherwise we are going to have a hard time isolating cause and effect.

By this logic, we should probably start with water at the same temp as the coffee and then begin to alter the temp.

It makes sense to use weight for both coffee and water - but I'd also like to see if and what the increase in volume is going to be rather than just changes in weight.

I would love, love, love to see any research (even tangential) that folks can find.

I wish that I could find someone with a bit more of a scientific background and bent to take this on. I'm pretty damn out of my depth here.

I think this could potentially yield some real results. We really need to start trying to understand each and every variable and each and every interaction if we really want to understand cause and effect and the results in the cup.
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Postby Peter Van de Reep on Sat Jul 02, 2005 9:22 pm

Though water quality will be a contributing factor, I think that the most sensible approach is to use water that has been properly treated/softened depending on the region's water source. So (hypothetically), Chris runs his tests in Portland, Alistair runs Vancouver trials, I do some in Calgary, etc. The results can be compiled and analyzed, with each region's results stating their water source/treatment. Using distilled reduces the practicality of the test, but could be more theoretically applicable.

Chris, I will pass on some pdf files of research papers. As far as I know, they are tangential to the max.

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Postby xristrettox on Sun Jul 03, 2005 12:27 am

ahhh..... a barista forum. this is the stuff I have been looking for!
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Postby Deferio on Sun Jul 03, 2005 12:04 pm

Good discussion...Hey Guys...
We will do some experimenting with this as well.
Two things to add to the to do list ....
1. I think we should use the automatic touch pad on the espresso machines used (if there is one) to garuntee that a certain amount of water has passed through and into contact with the coffee.
2. Before the extraction....
scale 1...weigh the amount of water put out with the touch pad ...then tare the shot glass. then on scale 2...tare the porta and weigh the dry puck before extraction on the second scale.

After the extraction...

1. weigh the shot glass and record weight and volume...

2. then weigh the portafilter with the spent puck in it to determine the amount lost to saturation.

I think the spent puck and the extracted shot should make up each others weight difference and will help us graph the differences in each coffee fairly accurately.

If we are going to detrmine the coffees abilities to resist or recieve water then we must keep very detailed accounts of where all the water went for each coffee.

Lovin this Forum!
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Re: hydrophobic coffees vs hydrophilic coffees

Postby Andy Schecter on Mon Jul 04, 2005 5:39 pm

malachi wrote:so... the question then becomes - what determines the hydrophilic nature of certain coffees?
thoughts?
implications?


Malachi, the term "hydrophilic" is a highly technical one, and it may not be the best to use in this discussion. Correct me if I'm wrong, but I think you are talking about two distinct properties of ground coffee:
(1)how much water can it hold, and
(2)how much does it expand when it absorbs this amount of water?

These are not the same; a coffee that expands the most may not necessarily hold the most water. But each could be expressed as a ratio:
(1) wet coffee weight / dry coffee weight
(2) wet coffee volume / dry coffee volume


#1 is relatively easy to measure; scales are accurate and easy to read. #2 will be harder to get a handle on, because small volumes are difficult to measure accurately.

When testing this, I believe it makes sense to add just enough water to the coffee so that it is completely saturated, but no more. Once liquid extract starts to leave the coffee, it carries solids with it, and these missing solids will greatly complicate your measuring process.

I suggest doing this experiment right in an espresso machine using a bottomless PF. This way you'll be doing it under actual extraction conditions. Here's one way to do it:
(1)Dose and tamp per usual, measuring dry coffee weight and volume as accurately as possible.
(2)Begin an extraction, using a narrow gicleur orifice or simply "goosing" the brew switch on and off so that the brew water comes in a little slower than usual.
(3)Cut the shot off manually JUST AS THE FIRST DRIP STARTS TO LEAVE THE BOTTOM SURFACE OF THE BASKET.
(4)Remove PF from machine, carefully weigh and measure expanded volume of saturated puck.
(5)Calculate wet vs dry coffee weight and volume ratios
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Postby Andy Schecter on Mon Jul 04, 2005 6:00 pm

xDeferiox wrote:1. I think we should use the automatic touch pad on the espresso machines used (if there is one) to garuntee that a certain amount of water has passed through and into contact with the coffee.
2. Before the extraction....
scale 1...weigh the amount of water put out with the touch pad ...then tare the shot glass. then on scale 2...tare the porta and weigh the dry puck before extraction on the second scale.

After the extraction...

1. weigh the shot glass and record weight and volume...

2. then weigh the portafilter with the spent puck in it to determine the amount lost to saturation.

I think the spent puck and the extracted shot should make up each others weight difference and will help us graph the differences in each coffee fairly accurately.

If we are going to detrmine the coffees abilities to resist or recieve water then we must keep very detailed accounts of where all the water went for each coffee.


Hi Chris:

I bought a little scale specifically for measuring this kind of stuff. The scale's got a 2600 gram capacity and resolves 0.1 grams:
http://balance.balances.com/scales/844
Very good value for the price, hasn't died on me yet. It has a high enough capacity so that you can place an empty PF and basket on the scale, tare back to zero, dose and tamp, then reweigh to accurately measure your dose. After the shot, you can place the PF back on the scale to measure the weight of the spent puck.

Although an automatic machine with flowmeter can make certain experients easier, I don't believe it's necessary for what you've outlined. Here's the weight equation:
(dry coffee) + (water added) = (spent puck) + (espresso)

If you weigh the puck before and after the extraction, and you weigh the espresso generated, you'll automatically know the weight of water added.
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Postby tonx on Mon Jul 04, 2005 9:58 pm

Chris -

So lets say hypothetically that you've done some experiments and have some results. What are the potential implications you see coming out of this? Can you sketch us a scenario?
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Postby malachi on Tue Jul 05, 2005 9:17 am

I have theories but I'd rather not share them yet for fear they'll compromise results.

Basically, I just want more real data and less myth and assumption.
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Postby deCadmus on Tue Jul 19, 2005 8:45 am

I'd think you'd have to control for:

1) Roast. I'd intuit that coffees with a darker roast would have more breakdown of cell walls, making them "spongier" (hygroscopic). Plus, they'd likely also have a lower level of remaining moisture, ergo (maybe) a higher capacity for absorbing / adsorbing more.

2) Age post-roast. Similar characteristics.

3) Method of quenching? Water-quenched coffees would almost certainly begin w/ greater moisture level.

At the very least I'd think you'd need a moisture meter to measure levels up-front...
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