Posted Tue Nov 27, 2012, 6:27am Subject: Temperature and Immersion/Steep Brewing
Been playing around with strike temperature and immersion brewing (AeroPress and CCD).
Haven't been doing fully structured experiments, but more of a guided exploration of brewing temperature. These are tasting based on my own and my wife's palate - your experiences will definitely vary. Most of these are based on a 16 water brew ratio, with a target range in strength of 1.17% - 1.25%.
Conventional wisdom says if temperature is low enough, proper "extraction" cannot be achieved. Surprise to myself - I found this is not the case. I started down this investigation path while trying to understand the relationship of time, temperature, grind and resulting extraction.
What I've been doing with several coffees recently is attempting to achieve 19%-20% extraction (as defined by immersion brewing calculation, where all of the water is considered solvent and E = (S * R) / (1 - S) where E is Extraction, S is strength, R is water brew ratio) for a wide range of strike temperature for the brew water.
There is a fairly sharp breakpoint where the taste character changes, even if the extraction ends up at 19% - right around 140°F-170°F. Below this is the traditional simplified character of cold brewed coffee (which CAN be extracted to 19% by grinding fine, on the verge of espresso, and allowing a long steep time), a trend toward smoothness and a loss in complexity. Indications are lower acidity given my cheap pH meter. Brightness is very muted if present at all.
The taste character from 170°F strike temperature on up to about 190°F seem to be a surprisingly good balance of flavor, sweetness (if in the varietal), increasing complexity, and a gradual increase in a little bitter bite. I didn't expect this. Some fruitiness of Tanzania and Ethiopia seems to peak around 190°F. Brightness is slightly reduced from higher temperatures, but can be present but reduced in intensity in favor of light sweet flavors.
From 190°F to 202°F is pretty decent, with the higher strike temperatures trending toward increasing bitterness, increased smoke flavors in darker roasted coffee, noticeably more oils at times in the cup. Many times these temperatures tend to percolate slightly faster given same grind, but to avoid strong or over- extraction, the grind seems to want to be somewhere between drip and french press if steep times are much more than 100 seconds. Fine grind and shorter steep times seem to be harsher and less balanced than slightly coarser grind and slightly longer steep times.
Right around 205°F strike temperature and above, most coffees take on a significant acrid taste, bitterness, and increased astringency and long finish. At times, it also seems to have a lingering oily feel on the tongue - the cup of coffee where you feel like you need to brush your teeth right after drinking it to avoid bad coffee breath.
In general, the hotter temperatures require coarser grind to avoid extractions exceeding a calculated 22%. Lower temperatures require longer times and finer grind - but there seems to be a grind/temp/time solution that allows 19%-20% extraction for nearly any temperature of the brew water. The solution set narrows for lower temperature - you have to grind fine to achieve long-term steep extractions of 19-20%, unless you jumpstart the brewing with at least 170°F water. Higher temperature brew water can have multiple solutions of grind and steep time to achieve same extraction.
However, the coffee resulting from 19% extraction for strike temperatures of 75°F, 120°F, 150°F, 170°F, 180°F, 190°F, 205°F and 209°F may have significantly different character, complexity, fruitiness, bitterness, brightness, and finish - even though they are similar strength and extraction.
What's the right answer? In my mind, there is none - because there is no right answer for which restaurant class is better (Chinese, Italian or American Chophouse - which one is "right"?). There is no right answer for the best color (red, no blue... ahhhhhhhh!). <180°F for the AeroPress? For some people. Personally, I think the temperature needs a slight boost to hone in on more of the varietal fruits, because that's my preference. Some people love the hearty earthy flavors that seem to shine for Sumatra coffees around 200°F - it's all how you want to craft it.
Some people love IPA, others love thick black lager. Still others like adjunct beer - what's the "right" answer?
Personally, I've been trending lower in my brewing - probably now averaging around 190°F strike temperature in a non-preheated AeroPress or CCD.
Just goes to show, just because some expert organization establishes guidelines or rules doesn't necessarily make them "laws". Brewing coffee - good coffee - does not REQUIRE the temperature of the brew water to be between 195°F and 205°F.
My advice to those starting out with brewing good coffee:
Concentrate on consistency.
to achieve consistency, you must be precise - this is more important in single cup brewing than it is for whole pots. Changes in strength - especially when jumping down into the rabbit hole of brewing coffee - can be misinterpreted as changes in taste character.
Don't sweat about temperature - just be consistent and work around that setpoint. Brewing coffee is a balance of contact time, grind, and temperature. Percolation (like pourovers) are slightly more complex because the contact time is a combination of how fast you deliver the brew water and how fast the percolation rate is.
Right now, my current thinking is that grind is probably the most important parameter to control - time and temperature are easier to control with a stopwatch alone. Just off boil in similar conditions plus a certain amount of time equals a particular temperature give or take 5°F.
------------------------------------------ ----------------------------------------- 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
Suricat Senior Member Joined: 25 Dec 2012 Posts: 2 Location: Québec Expertise: I live coffee
Posted Tue Dec 25, 2012, 8:26am Subject: Re: Temperature and Immersion/Steep Brewing
Very educating post. Thank you for taking the time to 'measure' all this. I realize that your means of measurement is not precise -- your taste buds and your nose -- but at least, it is honest and with no economic interests!
I've been reading many articles about water temperature for the initial strike that MUST be so and so for great coffee or else you drink a 'putrid concoction' (''and you don't know about it because you are not one of us' kind of think.). And that only this or that machine can meet.
In my capacity of EE, I cannot help to think attaining a specific water temperature is in no way a voodoo act but rather a simple selection of the heating element and proper piping. You nailed it exactly right when you say that electing the best coffee is like electing the most beautiful colour. The best coffee is indeed the one you love and savouring at the moment. There are better ones and less better ones, but amongst the better ones, no one coffee machine can claims it is it.
This is why coffee loving is so involving: There is no one correct recipe and no one can claim he's found the holy grail.
Posted Wed Dec 26, 2012, 7:56am Subject: Re: Temperature and Immersion/Steep Brewing
Great post! As I travel with my aeropress, I find your tests on brew temp very interesting. I've always used a heated aeropress and water around 203-205 - assuming that the temp declines a lot.
I need to begin experimenting with not pre-heating and temps around 195-198. Just used 198 and no pre-heat. Only noticeable difference is a touch less bite and a smoother more savory sweetness.
It compliments a sweet coffee well (Uganda/Ethiopia). If you're looking for dark broody coffee, then a higher temp on a dark roasted earthy Sumatra might be a better choice - but now you have another knob to accent or alter the 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
Posted Thu Dec 27, 2012, 3:45pm Subject: Re: Temperature and Immersion/Steep Brewing
I went with 197-198 again and the fruit flavors were extremely savory and juicy. This is a big Kenyan absolutely filled with currants and raisin. Need to try 195 now and see where it goes from there. I'll admit that I am still preheating a bit and want to cut it out to see how it goes. Ultimately, the lower temps and no preheat make travel brewing easier.
CheapBastid Senior Member Joined: 3 Dec 2012 Posts: 59 Location: Los Angeles Expertise: I like coffee
Espresso: None Grinder: Talking myself into a LIDO Vac Pot: None Drip: Mr Coffee Roaster: None
Posted Wed Jan 2, 2013, 11:29am Subject: Re: Temperature and Immersion/Steep Brewing
Netphilosopher - Thanks for this and your other measured and informative posts!
Developing a renewed focus on how to standardize the process to get a consistently enjoyable cup has made me appreciate your experimentation and posted results.
Pourista Senior Member Joined: 20 Dec 2012 Posts: 15 Location: Davis, CA Expertise: I live coffee
Espresso: Mishka's Medium Roast
Posted Thu Jan 3, 2013, 2:38pm Subject: Re: Temperature and Immersion/Steep Brewing
Thanks for that informative article. I'm eager to experiment with these ideas, but I have somewhat of a rookie question. In the immersion equation where S is strength, how do I measure that? Does that refer to grams of coffee or something else?
Posted Fri Jan 18, 2013, 8:58am Subject: Re: Temperature and Immersion/Steep Brewing
Sorry. Been offline for a while because of a data issue.
S is strength, and is the mass fraction of dissolved solids in a coffee solution.
If you have 100g of coffee in your cup, and you measure strength at 1% (or 0.01), then the coffee in your cup consists of a solution where 1gram of coffee (called Total Dissolved Solids) is dissolved in 99grams of water.
(also, you can think of it as 1 / (1+99) too - same thing).
There are a few ways to measure strength:
-Old method of using an estimate based on conductivity of the coffee. This method has fallen out of favor due to variability and issues with repeatability and precision. -Take a sample of your coffee, evaporate the water, and measure the residual mass left behind. Think of this as a more direct measurement of Total Solids - but keep in mind that if it comes from a sample that hasn't been well-filtered, it might contain a small amount of UNDISSOLVED solids too.
The favored method is measuring the index of refraction of the solution, using a calibration table or software to convert the amount of refraction (which changes as the coffee concentration, or strength, increases) to a Strength.
------------------------------------------ ----------------------------------------- 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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