I started to take a closer look at the extraction rates of Cold Brew Coffee or Cold Brewed Coffee.
This is considered a low temperature brewing process, which supposedly provides a coffee that is lower in acidity and improved smoothness. Curiously, these are also the type of claims made for the Aeropress in terms of taste.
Looking at many of the do-it-yourself sites and commercial cold-brewing sites (like Toddy), I found a fairly wide variety of parameters, some saying drip grind is ok, some saying the grind had to be larger or smaller than drip. Typical ratios are 8oz coffee to 36 oz water, 1lb of coffee to 72 oz water, 1lb coffee to 64 oz water, 10-11oz per 9 cups or 72oz water, and even a few that push the boundary to as high as 1½ cups (12 oz) water to 4 oz coffee.
What this works out to is a brew ratio that varies between about 13% to about 33%, so I set up 3 different brew ratios to check extraction and yield - and to see what it did to flavor.
Brew 1 is set to 15% brew ratio, Brew 2 set to 21% brew ratio, and Brew 3 was set to 35% brew ratio.
I let all three steep in the fridge for 24 hours, then used the Aeropress to separate the fines and recover the grounds, and then sampled the brews, diluting to my taste of approximately 1½% strength. I then dried all three sets of grounds to determine extraction, and brewed one additional 21% batch just to do an evaporation test to confirm that my method still worked (and it still does - all grounds accounted for, all solids accounted for).
The beans were all the same - a Panama roasted to FC+ personally, nice not-too-complex but good mouthfeel, somewhat apple with nut essence in the flavor. Touch of maple, nutmeg in the finish. Yum. They were all ground to approximate Aeropress grind (slightly finer than drip, on my modified Hario Mini Mill)
------------------------------------------ ----------------------------------------- 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
Surpisingly decent, definitely not bitter, no real hint of smoke or roast character. Some malty flavor, lacks the crispness of the variety evident in a normal temperature cup.
Brew 2 25g coffee 119.0g water 21% Brew Ratio
60.5 wet grounds mass 81.1g Coffee Yield 20.9g Dried Grounds
There is some indication of sourness, a bit of nutty flavor (think walnut shells), some "musty" character, absolutely zero citrus fruit or floral character. Aroma is about as bland and uncomplex as coffee gets. Extremely smooth, zero bite or brightness, zero smoke. No varietal character.
Brew 3 25g coffee 71.4g water 35% Brew Ratio
58.2 wet grounds mass 35.1g Coffee Yield 21.5g Dried Grounds
Sour, musty, pungent, heavy pecan-like overtone, with an overall oil-ness (similar to vegetable oil taste of sorts). Heavy molasses-like flavor. still fairly "smooth". Definitely not very high in acidity, definitely not "bitter" per se, but off in overall flavor profile.
------------------------------------------ ----------------------------------------- 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
I was surprised at Brew 3 - especially the underextraction, so I took the dried grounds, and did an inverted Aeropress 2:00 contact time brew just to see what came out of the grounds next - (figuring that I could pull the next several percent out, since there were obviously more dissolved solids in the grounds - and I wanted to know what these taste like)
Re-Brew 3 21.5g coffee 123.3g water 17.4%? Brew Ratio
49.0 wet grounds mass 93.5g Coffee Yield 19.0g Dried Grounds
2.5g Extracted Coffee Solids 11.6% Extraction (actually the total extraction of the grounds has been pushed to 24% from original, so this is the extraction from 14% to 24%, or the next 10% of solids) 2.7% Strength
Since I tasted this batch before I knew what the solids were, and guessing it would be lower, I only added about 90g of water to start, and planned on diluting to 1½% by taste, if I could. Sniffing it, there was a small element of smoke, but also a hint of some of the classic Panama aroma - but just a hint. A waft of malt or apple... but then gone. BLECHHH! The first thing that hit me was the bite, then nasty bitterness with smokey creosote tones and an actual gasp of surprise - how nasty and weak! If I worked really hard at it, I could see that some of the varietal character was there, but so was boiled pencil shavings, cedar, and that ever present bitterness and smoke. Holy crap was it awful.
------------------------------------------ ----------------------------------------- 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
So, now I knew that the 15% brew ratio recipe had a decent chance at some useable extraction, I wanted to find out how this brewing method affected the taste of some different coffees:
So, I then went ahead and used the 15% brew ratio recipe - the best of the three - to brew up samples of Caribou Guatemala, some of my India Giri-Region (self roasted), a sample of *$s 3-region, *$s Pike Place, some Dunkin Donuts medium, and some Eight O'Clock Colombia. These are a fairly nice variety of coffees, all with as exactly as I could get 25g of coffee with 166.6g water, all steeped in fridge 24 hours and all diluted with 170g of water after separation of grounds.
All of these yielded around 110-130g of coffee, and the balance for the most part was in the puck - a variance of the amount of water still stuck in the grounds. When diluted, these coffees were all the same strength by taste.
Yes, I had 6 little glasses each with some coffee in it in the fridge. I know, but hey, all in the name of science and pursuit of good coffee.
The Caribou Guatemala was first up. Sip - some good smoothness, but vaguely familiar - like the Panama I made the day before. Smooth, nice body. Coffee. If I concentrate, yep there's a hint of nuttiness, but mostly just good old-fashioned coffee. Very much like a decent Colombia.
India, already a decently smooth coffee, was... smooth. Low acid, no brightness, similar to the Carabou Guat. Hmmm. Another sip and the same. Where's the hint of exotic origin? The chocolate/Cocoa? The nutmeg and cardamom hints? Nowhere to be found.
Rinse my mouth out... four more to try...
Try the Dunkin Donuts Medium next. Hmmm, not bad. Nice, smooth. Low acid, no bright..... hey, wait a minute....
Starbucks 3-region, wait, there it is... nope. Same good smooth low acid uncomplex coffee. Eight O'Clock... Dunkin Donuts... did I mess up the cups? Did someone come in and change everything over to Colombia coffee?
In fact, the only thing that really had any distinct character was the Pike Place - and I think that's only because of a slick of oil on top of the coffee that didn't seem to be there for the others. Just a teensy hint of roast/smoke - but it was only in the background (unlike normal *$s, with in-your-face-all-coffee-is-dark-roasted character).
Tasting these in rounds, I found that I actually lost track of the Guatemala and the Eight O-Clock - in the end I don't think I could have picked which coffee was which by taste except for the *$s Pike Place.
My conclusion from all of this is that Cold Brewing extracts the first 15-17% of the basic flavor profile of what we think of as coffee, and leaves behind (does not extract) some of what gives the different varieties character and complexity. It also leaves behind the partial combustion components of roasting.
The basics of coffee flavor seem to come from the first 16.5% of extraction, the next 2.5% of extraction (16.5% to 19%) picks up the varietals and other aromatic oils, and some of the acids that may be locked in the grounds (above 18% or so). I think you can only get to these with water in the 180°+ range. Continued extraction brings about the caramels, caramelized sugars, and roasted compounds (from 19%-22%), and then past that, continued extraction brings out the converted oils of the cellulose and scorched products of the bean structure (past 22%).
If you're planning on underextracting (using the Aeropress with low brewing temps and 10 second contact times, or cold brewing, just as a couple of examples) save your money and just buy supermarket beans. There's no sense in buying hi-quality La Minita Peaberry or Ethiopian, or getting some exotic and roasting it yourself, then throwing away the part that distinguishes the varietals AND the roast character from each other. You can get decent, smooth, low acid straight up coffee with run of the mill beans at medium roast using consistent underextraction methods.
Disclaimer: of course, this is all subjective (except for the measurements of the weights and process of brewing - that's objective), so YMMV when it comes to taste.
------------------------------------------ ----------------------------------------- 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
BTW - what started me on this is I gave a friend some of my personally roasted coffee. They made it into cold brew (all 11 oz of it), and then when that batch was almost gone, they went and brewed some generic (like Eight O'Clock)... and they told me they couldn't really tell the difference. It was really smooth and really good, but not much difference.
That was puzzling - I pushed the roast further into FC territory than EOC does, I provided some coffee that has had rave reviews with many of my friends (even some brewing in Keurig) - and they couldn't tell the difference when everyone else could. Something was definitely up, and so lead to this investigation.
------------------------------------------ ----------------------------------------- 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
Posted Sun Jun 12, 2011, 5:29pm Subject: Re: Cold Brew Coffee Experiments (or puttering around)
Great info.......I wish I had the time and/or inclination to do such things too.
Have you read (I think it was) Ken David's recent article on cold brewing ? ......accordingly, you can't get good taste unless you have the right temperature of water to have the necessary reactions and extraction.
I have considered it - but since in taste there doesn't seem to be much difference between 6, 12 and 24 hours steeping (previous times I made cold brewed coffee), and there are some that do an Aeropress cold brewed coffee in 20-30 minutes, claiming good results (my results tend toward severe underextraction, but whatever floats yer boat), I figure most of whatever will be extracted is probably happening within the first 6 hours.
Warm priming and cold brew finish isn't really much different than a full extraction and cooling the concentrate coffee. This is a well known double-strength method for the press pot - make double strength coffee by using double brew ratio, refrigerate the result and use as a 1:1 concentrate later. Outlined out on the web and in Kevin Knox's book "Coffee Basics". It makes a decent 3ish% coffee concentrate.
In fact, sometimes when I don't think I'll have time in the morning to grind and properly I-Aeropress (that's Inverted Aeropress) a cup, I use my 5% strength recipe and make a cup or two the night before. Then, I simply refrigerate the 95-100g of resulting coffee with some plastic wrap on top. In the morning, I just nuke up another couple hundred grams of water to boiling and add to the cold coffee, and voilà - darn near perfect cup. That isn't much different than hot priming a cold brew batch - especially if the latter cold brewing isn't doing anything at all. It only misses a little bit of floral character (probably missing aromatics that evaporate out during the brewing and cooling process), but keeps much of the brightness and acidity.
The other reason I think cold brewing stalls out before full extraction is that I have, on occasion, tried to cold brew already-brewed grounds. The several times I have done this, it's failed miserably. I end up with very transparent, brownish, horrible tasting water. Once the first 16% is extracted, ain't enough energy to extract anything else with ambient temperature water. This is really no different than properly extracting, creating coffee concentrate and cooling the results - if you leave the grounds in overnight, they aren't going to extract any more anyways. You'll still have to separate the grounds in the morning, so why not just get that part done the night before?
I suspect the coffee solution reaches saturation at higher concentrations and low temperatures, which seems to be why boosting the brew ratio results in lower extraction - there's only so much that can be brought out of the solids and into solution without extraordinary measures.
------------------------------------------ ----------------------------------------- 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
I also did one more this weekend - pushed a small batch of India well into near-vienna (just a hundred grams). Beans all nice and oily, very dark and smoky. Beautiful batch emulating the darkest of a *$s Sumatra.
Had enough for 3 cups (couple days rest) - normally extracted (inverted AP), very full flavor and smoky - a homey kind of smoky, not the burnt or scorched flavor I expected, but definitely overlaying the flavor. Some not too unpleasant bitterness accompanied by a very nice toasted caramel/cocoa reminiscent of a s'more without the marshmallow.
Aeropress "recommended" - smoke and bitterness muted - but so was a lot of the cocoa notes. Some varietal character, body not as thick as normal extraction. Some touch of malt, unexpected.
This morning, cold brewed results from overnight (about 12 hours). Yep - basic coffee with only the slightest hint of anything resembling bitter. Lacking in complexity. Not bad but not much different than just about any run-of-the-mill coffee.
I think that personally, I'm probably done with cold brewing coffee - the cheap engineer in me sees it as a waste of potentially extractable solids. LOL
------------------------------------------ ----------------------------------------- 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
Perhaps, what you may have also discovered is a good use for beans that are past their prime, on the verge of staleness. I find that I enjoy using cold brewed coffee in my iced coffee drinks, be it an iced latte or my own version of a blended frappe. I'm not looking for the coffee's origin or varietal character to shine through, only for the satisfying taste of coffee itself mixed in for a nice refreshing and energizing drink.
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.
= No New Posts since last visit 