Posted Sun Jul 10, 2011, 1:55pm Subject: More observations on Coffee Brew Water Hardness
So, I've been experimenting with brewing water with various hardness. I eventually got a water test kit for GH and KH (total harness and alkalinity).
My cold tap water is about 340ppm GH, 275ppm KH.
After boiling for 4 minutes and filtering the results, it's down to 255 GH, 240 KH.
I had been using a mix ratio equal parts cold tap water to distilled to get what I assumed to be ~275GH down to about 150ppm GH, but I was probably more in the 175ppm range.
Regardless, I've done enough to convince myself of a couple of things:
-Extraction using an AeroPress (and confirmed on a couple of Press Pot brews at the extremes) is unaffected by distilled to very hard water (up to 250+ general hardness). TDS of dried coffee grounds, and likewise evaporation of brewed coffee in a range of strengths has no correlation to the type of water used.
-Water hardness has a NOTICEABLE effect on taste from distilled to about 140ppm. Past that, the taste does not seem to be affected significantly. This is based on personal observation and popping "blind" samples on my wife and watching her expressions... LOL
Here's the interesting thing:
If you brew two cups with identical parameters (grind size, brew ratio, contact time, filter) to 4% strength, one distilled and the other using maximum hardness water, you'll taste a difference. Descriptions of the taste is the harder water brew is more "smooth" or "balanced", the distilled water brewed is more "bitey" or "harsh". Not exactly bitter. I describe it as more acidic or harshly bright in nature, my wife sees it as strong, or has more "bite". Sometimes it's described as maybe "soapy" (her term, not mine).
Here's the kicker: brew two cups of 4% strength coffee with distilled water.
Sample 1) Dilute one cup with distilled water to 1.25% strength.
Sample 2) Dilute the other cup with hard water to 1.25% strength.
Then, brew two cups of 4% strength coffee with hard water.
Sample 3) Dilute one cup with distilled water to 1.25% strength.
Sample 4) Dilute the other cup with hard water to 1.25% strength.
My thinking is that if the hardness of the water affects the extraction, then there should be a clear distinction between these two methods of BREWING, but not by the water used to dilute. I expected samples 1 & 2 to taste like "distilled" is described, and samples 3 & 4 to be smoother or more balanced.
Instead, of course, contrary to prediction, the only definitely different cup was sample #1, the brewed distilled/diluted distilled. #2 was indistinguishable from 3 & 4. This seems to hold up even through different bean types and flavor profiles, as I have had to do this multiple times, in multiple configurations - the only cup you can pick out time and again is distilled/distilled.
I went back to try some of these on cold brewed coffee again, as well as lower temperature "Aeropress recommended". When brewed this way, the taste is described as "smooth" and very "coffee-like". I personally see the same muted varietal character that I've noted in other threads and posts on the subject. I also see no big differences in using distilled or hard water, either to do the brew or to do the dilution to normal strength with underextracting methods. Of course, we know that these methods of brewing are prone to or automatically underextract.
From here, I can only conclude that the hardness in water acts upon the coffee extracted from 17% to 20% extraction - the bulk of the extraction that seems to contain flavorful acids, varietal character, aromatics, etc. - the very things that lower temperature underextraction brewing methods don't extract. Furthermore, the hardness of the water acts upon these components AFTER extraction, and does not affect extraction itself.
I went one step further, doing a second extraction of underextracted grounds (eyes rolling, yep, once again). While the overextracted brew is still definitely nasty, strangely enough those that have some hard water added (regardless of before or after the extraction) seem to be a bit "better" and less nasty. Don't get me wrong, it's still somewhere between brewing charcoal and years old ground up tire rubber, but if it could be more "balanced" with the addition of a bit of hard water, it is.
My thinking is that somewhere after extraction, if there's acids in that 17%-20% of the extraction, perhaps they interact with the hardness ions or even the alkalinity buffering this acidity, similar to underextraction, but still allowing the aromatics to be extracted and remain with the flavor profile? (insert big shrug here)
Just thought people might find this interesting - since I have a hard time with hard water (no pun intended here) scaling everything (but I don't want to put in a distillation or RO system, and I can't stand "softened" ion-exchange treated water), including teapots, I use lots of distilled water for things requiring hot water, with moderate doses of heated tap water to add in "some" hardness. Lemme know if anyone has looked at it personally (not just the SCAA recommendations based on taste testing with no mention of differences in source hardness or alkalinity measurements).
------------------------------------------ ----------------------------------------- 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 Wed May 30, 2012, 6:07am Subject: Re: More observations on Coffee Brew Water Hardness
Revisiting with my new (VST) toy.
8 cups of coffee, varying water hardness, and the strength resulting from same coffee/brew process/brew parameters is...
...indistinguishable. It varies a bit, +/- a hundredth or two, but the difference between 1.38% TDS and 1.40% TDS doesn't follow the water. In fact, it follows variation in the amount of brew water I put in more than the PPM Hardness (from a test kit, results in DH * 17.9 to obtain PPH, did not bother to also measure the alkalinity).
The taste? Well, that's something that varies. A LOT.
Distilled is definitely NOT the way to go. Very unbalanced, biting, sometimes sour, could be considered bitter. Sensation of tingling on the tongue at the finish. The other interesting thing - it doesn't COOL well. As the distilled samples cooled, this quality became almost unbearable - it became more and more of this sour/bitter unpleasant flavor.
The difference between very hard and moderately hard, to within SCAA recommendations were ALMOST indistinguishable. The very hard samples were maybe a bit flatter, with more of an emphasis on chocolate and cocoa and nut tones and a slight muting of brightness. The very interesting observation (that I don't know if anyone else has noticed) is that the samples made with any calcium hardness COOL a lot better. The harder ones may actually cool the best (by this I mean that it doesn't develop into something very sour as the coffee approaches room temperature).
The brew ratio moves around a bit (using 15.00g of coffee, and attempting to get the brew water at 200g but it varies by +/- 2.5g or so - once the water is "in" ya can't pull it back "out" LOL ) and the mathematical strength based on the same extraction is much more sensitive than I had anticipated (2g difference in brew water, given same extraction, is a change of 0.01% TDS). I define the brew ratio as the original coffee (very easy to establish at 15.00g) subtracted from the brew mass, where the brew mass is measured just prior to pressing.
Again, the other interesting thing - if you brew with distilled water, and just add a dollop of hard water, the harshess diminishes SIGNIFICANTLY.
My water is pretty much 100% calcium hardness and that's also the primary source of TDS for my water. Some recommendations show a much higher TDS (in PPM or g/l) than "hardness" (also in PPM or g/l). TDS is ALL of the solids that would be left behind if you evaporated a given amount of the water (includes salts, sugars, organic or inorganic materials, sulfur, iron, calcium carbonates, magnesium, silica dust, etc.).
The "hardness" is the Calcium and Magnesium components of the TDS.
So, while the hypothesis (or conventional wisdom) is always the "extraction" is affected by water hardness and TDS, I propose it's something else. If the extraction was really affected by hardness, the strength changes at 7.5% brew ratio would be on the order of 0.09%TDS for EVERY PERCENTAGE CHANGE in extraction. If I obtain a strength of 1.40% and it's extracted at say 18%, and I brew a second cup that is extracted to 19%, I would expect a change in the strength to about 1.47-1.49%. Based on my quick check, this is definitely NOT the case. All of the brews were within 1.38% - 1.40% (which made me wonder for a second whether the VST is that repeatable, but I've done enough to convince myself that indeed, it IS that repeatable of an instrument).
Stated another way, if changing hardness of the water from 320ppm to 0ppm makes a change of +1% or -1% in extraction (say ranging from hard to soft changes the extraction from 21% to 19%), then we would expect a range of strength of about 0.18%. If the average strength is 1.40%, we'd expect the range (if extraction is affected) of the strength to be from about 1.50% to 1.30%.
There's some things that we know about coffee:
-it contains Chlorogenic Acid. CGA by itself is not completely tasteless but at concentrations in coffee it doesn't contribute to taste. -Heat decomposes Chlorogenic Acid into quinic and caffeic acid. THESE compounds are KNOWN to affect taste. Some people perceive this taste as sour, others as bitter, some consider it similar to earwax - in high concentrations. In lower concentrations, these are part of the "character" of coffee, and are necessary for full flavor profile. -Heat sources that decompose CGA come from roasting, and also from brewing. Time spent at moderately high temperatures of brewed coffee converts much of the CGA into its byproducts, and is thought to be responsible for much of the flavor changes of coffee kept in thermos or on a burner.
I'm suggesting that the alkalinity of calcium carbonates in water acts as a "buffer" for either CGA or its acidic components. If it neutralizes chlorogenic acid into something semi-inert, then it may be prevented from converting to the decomposition byproducts. Alternately, if calcium carbonates interact with the byproducts themselves (quinic and caffeic acids), it may neutralize the taste that these compounds create. Maybe it's both - if CGA is extracted but then neutralized before it is heated up, then maybe this kills brightness (like what can happen with cold brewed coffee).
This would also make sense if adding eggshells changes the taste of brewed coffee (which it can), and would also potentially explain why you can add hard water AFTER you've brewed it and affect the taste (which you can).
Regardless, 100% distilled or very low TDS/Hardness water shouldn't be used if you're expecting decent coffee. You need some hardness or you will end up with unbalanced and potentially unpleasant coffee.
As always, YMMV - don't trust my taste buds. Try it yourself - replicate the experiment. It's why I post this stuff. This just happens to be stuff that I've learned along the way.
------------------------------------------ ----------------------------------------- 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 Wed May 30, 2012, 6:07am Subject: Re: More observations on Coffee Brew Water Hardness
When I get a chance, I'll try and post a couple charts, but they aren't that spectacular.
Edit: Initial look at correlation of strength vs hardness.
(Click for larger image)
------------------------------------------ ----------------------------------------- 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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