JustAcoffeeDrinker Senior Member Joined: 11 Jul 2010 Posts: 35 Location: Ottawa, Ontario, Canada Expertise: I like coffee
Posted Sun Sep 16, 2012, 11:32am Subject: Over-extraction in a pour-over coffee cone
I read that coffee releases different flavours as brewing time passes. If your grinder (say, blade grinder) creates nonuniform chunks of ground coffee, the smaller pieces can over-extract while the larger chunks under-extract.
I use a Melitta #2 single-cup plastic cone that I put a paper filter into, then place the whole thing on top of a cup. The grounds go into the filter-lined cone, then I pour water through. The recommended grind is fine.
It seems impossible to over-extract because the coffee goes through once and the extraction time is pretty constant. It depends marginally on how fine the grind is, but not much.
Assuming that the extraction time is roughly constant, then I guess I can over-extract by grinding too fine, since optimum extraction time decreases with the fine-ness of the grind.
Also, sometimes I make a *large* cup of coffee, and I find it necessary to fill the cone up twice with water to fully fill the cup. I guess I can over-extract that way too, since this doubles the extraction time. Wouldn't this mean also that bigger pour-over cones are at risk of over-extracting as well, since they also increase the extraction time? Unless there are more holes at the bottom of the cone to increase the water throughput and maintain optimum extraction time in the face of a greater volume of water going through.
Do the above 3 points seem reasonable? (I'm enjoying my large cup of coffee nevertheless).
Posted Sun Sep 16, 2012, 2:27pm Subject: Re: Over-extraction in a pour-over coffee cone
JustAcoffeeDrinker Said:
I read that coffee releases different flavours as brewing time passes. If your grinder (say, blade grinder) creates nonuniform chunks of ground coffee, the smaller pieces can over-extract while the larger chunks under-extract.
I use a Melitta #2 single-cup plastic cone that I put a paper filter into, then place the whole thing on top of a cup. The grounds go into the filter-lined cone, then I pour water through. The recommended grind is fine....
It seems impossible to over-extract because the coffee goes through once and the extraction time is pretty constant. It depends marginally on how fine the grind is, but not much.
Absolutely not true. It is completely dependent on several factors, but what you're probably not aware of is the hot water sitting in the grounds is dissolving solids - even if you're not running fresh water through the grounds.
In pourover - your delivery time is dependent on percolation time, unless you're doing it like Starbucks. Starbucks dumps in the brew water and whatever time it takes to percolate into the cup is what the contact time is. This is pretty much like a quick (too short) immersion brew and will end up underextracted. It's basically a CCD with zero steep time.
A proper pourover matches the delivery rate to the percolation rate - there's the initial bloom pour, then add water in stages, striving to maintain a well-saturated (but not DROWNING) brew slurry. Many of my pourovers average about 7-12 dollops of water, and a nice little stir at the last dollop for the final percolation.
In the proper pourover case, grind basically determines delivery rate (because finer grind slows the percolation rate), so finer grind will overextract. I've been able to use fine grind and a pourover and achieve over 24.5% extraction in the cup with a normal 17.5 water brew ratio.
JustAcoffeeDrinker Said:
Assuming that the extraction time is roughly constant, then I guess I can over-extract by grinding too fine, since optimum extraction time decreases with the fine-ness of the grind.....
See explanation above. My CCD percolates at approximately 6-7g per second at coarse grind to well below 1g per sec at fine grind, depending on my filter choice. This means that I can percolate almost 400g of liquid through about 27g of brew coffee (dry ground coffee ready to brew) in one minute - or seven or more minutes, just by changing the grind.
JustAcoffeeDrinker Said:
Also, sometimes I make a *large* cup of coffee, and I find it necessary to fill the cone up twice with water to fully fill the cup. I guess I can over-extract that way too, since this doubles the extraction time. Wouldn't this mean also that bigger pour-over cones are at risk of over-extracting as well, since they also increase the extraction time? Unless there are more holes at the bottom of the cone to increase the water throughput and maintain optimum extraction time in the face of a greater volume of water going through.....
It all depends on what you want your end strength to be, and how much coffee you used. By adding more water, you're diluting (weakening) the brew ratio. And yes, in general, if your first pour extracted properly, adding more fresh water will just continue the extraction.
Hope that makes sense. Maybe you could post your own brew recipe (how much water, how much coffee, and how do you do your pourover). You didn't mention whether you do it Starbucks style (dump and perc, or zero steep/immediate release) or in delivery installments - and if so, how many (i.e. how long does it take for you to deliver your brew water).
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
JustAcoffeeDrinker Senior Member Joined: 11 Jul 2010 Posts: 35 Location: Ottawa, Ontario, Canada Expertise: I like coffee
Posted Mon Sep 17, 2012, 8:08pm Subject: Re: Over-extraction in a pour-over coffee cone
I was doing it Starbucks style. It tkes around 3 minutes for coffee to pass through. The total volume is 2 cups. I pour in a ladel to wet the (fine) grounds thoroughly for about 20 seconds, then fill up the cone (1 cup). As the water drains, just before the grounds stopped being fully immersed, I pour in the 2nd cup (after ensuring it's 94C (201F). Sometimes, the first cup has fully drained through the cone before I can get the 2nd cup up to temperature.
What's wrong with drowning the coffee grounds? Isn't that what a press does?
Posted Tue Sep 18, 2012, 6:41am Subject: Re: Over-extraction in a pour-over coffee cone
JustAcoffeeDrinker Said:
I was doing it Starbucks style. It tkes around 3 minutes for coffee to pass through. The total volume is 2 cups. I pour in a ladel to wet the (fine) grounds thoroughly for about 20 seconds, then fill up the cone (1 cup). As the water drains, just before the grounds stopped being fully immersed, I pour in the 2nd cup (after ensuring it's 94C (201F). Sometimes, the first cup has fully drained through the cone before I can get the 2nd cup up to temperature.
What's wrong with drowning the coffee grounds? Isn't that what a press does?
Last first - the CCD isn't that advanced. For $15, it's a great all-around brewer, simple to use. You can do it pourover style or steep and release.
Drowning the coffee grounds makes something called an "immersion" or "steep" brew. This is essentially what a press does, and it results in different strength of the end coffee for a given brew ratio. It can also lead to underextraction. If you're using the pourover brewer this way, then it is highly likely you probably won't overextract.
A pourover is supposed to be a percolation method - with a continual introduction of fresh brew water rinsing the coffee solution through the grounds. This is different than a drown and drain.
I'm sure that some people think this analogy is stupid, but I find it helps me think about brewing:
Think of the grounds as a dry bath towel with salt impregnated in it (like you soaked the towel in the ocean, then allowed it to dry). The salt is analogous to the coffee solids you want to dissolve.
Your method would take a bucket with a hole in the bottom, toss a few gallons into the bucket and allow it to drain. In your case, your adding a second cup is like adding fresh rinse water.
A proper percolation method would add fresh rinsing water into the bucket in a continual cycle - and the end result would be more complete rinsing of the towel.
A French Press would be like taking that towel, tossing it in a bucket, tossing some water in. Then, after some soaking time, you press the towel to the bottom and pour the "salty" water off of the towel.
The CCD would be like having a cork in the bottom of the bucket - you toss the towel in, toss the rinse water in, let it sit for a while, then pull the cork and allow it to drain.
The AeroPress would be like the CCD, except you get to press the towel more "dry".
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
JustAcoffeeDrinker Senior Member Joined: 11 Jul 2010 Posts: 35 Location: Ottawa, Ontario, Canada Expertise: I like coffee
Posted Tue Sep 18, 2012, 11:13pm Subject: Re: Over-extraction in a pour-over coffee cone
Thanks for that scientifically intuitive explanation. I couldn't hep but notice your rather scientific looking avatar. I bet that a rather complicated many-body simulation could be done on the extraction, but it would require a good model of the actual relinquishment of flavour by the grains of ground coffee, the diffusion of the flavour upward through the immersive hot water, and the flow of water through the bed of grounds. But I got the gist of it from your much simpler explanation.
Posted Wed Sep 19, 2012, 10:35am Subject: Re: Over-extraction in a pour-over coffee cone
JustAcoffeeDrinker Said:
Thanks for that scientifically intuitive explanation. I couldn't hep but notice your rather scientific looking avatar. I bet that a rather complicated many-body simulation could be done on the extraction, but it would require a good model of the actual relinquishment of flavour by the grains of ground coffee, the diffusion of the flavour upward through the immersive hot water, and the flow of water through the bed of grounds. But I got the gist of it from your much simpler explanation.
LOL - the avatar is simply a caffeine molecule, and although clever it certainly isn't original.
You can gain a surprising amount of insight about coffee with just your taste buds, a couple of consistent and FLEXIBLE ways to brew coffee, an accurate scale and a refractometer.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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