Green Coffee Buying Club
Vendor Discussion Boards => old Traveling road shows => Topic started by: ecc on February 26, 2011, 10:00:49 AM
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This was tougher to write up than I imagined. If you don't get it, it is likely because I am not explaining it well. Please ask questions!
(http://image.made-in-china.com/5f2j00GBFQlIncHLot/0-10-Brix-Scale-Refractometer-HY-101-.jpg)
The overview (poor mans extract mojo):
Optical refractometers have been used for a while to provide a practical and quick method of determining relative sucrose content of produce. Basically, if you can get enough light through a liquid, you can tell how dense it is by how much it bends light. The refraction is indexed onto a scale, various refractometers have different scales and ranges. Someone in a lab coat spends a huge amount of time correlating the refraction index to sucrose content, or tds in coffee, or you can just use it as a relative measure to compare between two samples.
Quick Directions for use:
-- Let a coffee sample cool to room temperature
-- use a pipette, a clean stirrer/straw and the finger over the top trick to get liquid up, or somehow drip enough liquid to cover the lower glass plate
-- gently lower the plastic cover onto the glass plate, you may need to do this a few times to eliminate bubbles between the lower glass plate and the plastic cover
-- point the business end towards a light source, look in the other end
-- the brix scale is indicated by the amount of the scale covered in blue
TDS is 85% of Brix, use this extraction chart (http://www.bunnomatic.com/pages/coffeebasics/cb4technique.html) as a guideline as to what the tds "should" be for your coffee:water ratio. Note how the 19:1 ratio has the biggest window of "acceptable" tds values. Please don't let this dogma blind you from the value of objective measure, comparison between brew methods, consistency, quickly adjusting grind for new brewing methods, etc. I end up always skewed to the strong side, but then my water:coffee runs more like 16:1 .
Enough for now, lots to talk about! Sign up for a spot in the travel loop, ask a question, or hit the flameguns!
Travel loop:
B|Java
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Cool. First port of call: Lake Cheddar.
I have the TDS meter figured out so I will run with the wolves and compare the two. Write up pending.
B|Java
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I've been intrigued by this and have wondered about the merit of its use for coffee. Would a refractometer show anything other than the percentage of solids in the coffee? How would this be useful when SO's have varying flavor characteristics that add to the coffee strength (mouth feel?)?
I'll be watching the results of everyone's use to see if I might want to use mine. BTW: A friend at A&M had a spare that I was be able to swap a Gaggia pump for years ago - now where did I put that bleepin' thing?
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Tex..
TDS meter gives you solids brix/refractometer is sugar.
As for your question of usefulness...depends on who you ask.
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Some interesting further reading, http://www.jimseven.com/2009/06/16/extractmojo/ (http://www.jimseven.com/2009/06/16/extractmojo/), and a corrected link to the brewing control chart (http://scae.com/images/PDF/coffee_brewing_control.pdf) mentioned in the middle of blog entry.
Here is a goldcup brochure (http://scae.com/images/PDF/scae_brochure_english.pdf) as well.
Brix is just the calibration scale used to display the refractive index. Most TDS meters measure ohms.
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Tex..
TDS meter gives you solids brix/refractometer is sugar.
As for your question of usefulness...depends on who you ask.
OK, then that begs the question: The same bean at different roasts will have varying amounts of dissolved sugars, so you'd use this tool to determine the roast level to aim for?
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Tex..
TDS meter gives you solids brix/refractometer is sugar.
As for your question of usefulness...depends on who you ask.
OK, then that begs the question: The same bean at different roasts will have varying amounts of dissolved sugars, so you'd use this tool to determine the roast level to aim for?
No, this is like expecting the electrical resistance to have the same correlation to tds in water vs. coffee. Remember, we aren't measuring sucrose or dissolved solids directly, we are using a (hopefully) well established relationship between those properties and something way easier to measure.
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Tex..
TDS meter gives you solids brix/refractometer is sugar.
As for your question of usefulness...depends on who you ask.
OK, then that begs the question: The same bean at different roasts will have varying amounts of dissolved sugars, so you'd use this tool to determine the roast level to aim for?
No, this is like expecting the electrical resistance to have the same correlation to tds in water vs. coffee. Remember, we aren't measuring sucrose or dissolved solids directly, we are using a (hopefully) well established relationship between those properties and something way easier to measure.
Good enuff reason NOT to go digging around in the garage.
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
I totally agree. I am skeptical as to the validity of an ideal and universal extraction rate, brewing concentration, roast profile, etc. I also suspect that the research and data backing the gold cup standard might not be the most rigorous. I don't think that precludes me from thinking the measurement is useful and/or interesting, and I do believe it has made my cup a little better.
This refractometer (0-10Br) is useful for brewed coffee only. It can measure how consistent your brew strength is from day to day, from method to method, from person to person. It can also provide a quick way to adjust grind/brew time for a new brewing method, or map/check approximate grind settings across grinders.
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
As a non chemist coffee fool I've been saying the same thing from the first time I ever heard about using TDS meters and refractometers with coffee.
Knowing how many PPM of random solids are in a cup does not tell me what they taste like. I see the usefulness for standardization but that is about all.
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
As a non chemist coffee fool I've been saying the same thing from the first time I ever heard about using TDS meters and refractometers with coffee.
Knowing how many PPM of random solids are in a cup does not tell me what they taste like. I see the usefulness for standardization but that is about all.
But, if someone has the same coffee, ground at the same coarseness, and the same water, can't they bracket their brew ratios, checking the PPM/brix of each one until they find a ratio that tastes 'right' and then use that ratio going forward and check with the gadget in subsequent days to see if the ratio is holding true?
How's that for a run-on sentence, complete with commas and apostrophes? Jeffo should comment now. ;)
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
As a non chemist coffee fool I've been saying the same thing from the first time I ever heard about using TDS meters and refractometers with coffee.
Knowing how many PPM of random solids are in a cup does not tell me what they taste like. I see the usefulness for standardization but that is about all.
Knowing the ratio of coffee to water does not tell you what it tastes like, nor does measuring the brew temperature, the brew time, or checking to see how hard/soft your water is.
Just another tool...
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But, if someone has the same coffee, ground at the same coarseness, and the same water, can't they bracket their brew ratios, checking the PPM/brix of each one until they find a ratio that tastes 'right' and then use that ratio going forward and check with the gadget in subsequent days to see if the ratio is holding true?
I can't figure out what you are asking and I'm still inclined to say no.
In fact I'm pretty sure it's no. ;)
Rephrase please....
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I'm pretty sure Peter is describing some baselining for 'standardization' of a single coffee.
I think John's answer will then be 'yes'.
:)
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I'm pretty sure Peter is describing some baselining for 'standardization' of a single coffee.
I think John's answer will then be 'yes'.
:)
I almost said that if I understand his question it's not any different than measuring in grams.
And yes, I am in agreement with the use of these tools for standardization.
I just don't have any personal need for standardization at this point in time. If I had a shop with teenagers running it and wanted to have a measure for general standards like what I think the Gold Cup was about then yeah, I might use it for that.
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Yeah, that was a long way of saying once other variables were removed and a brew ratio was chosen, a person could use the meter as a baseline quality control.
And yes, I am in agreement with the use of these tools for standardization.
I just don't have any personal need for standardization at this point in time. If I had a shop with teenagers running it and wanted to have a measure for general standards like what I think the Gold Cup was about then yeah, I might use it for that.
That's my stance too; use your palate to be the guide, unless you have employees doing stuff while you're not around.
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That's my stance too; use your palate to be the guide, unless you have employees doing stuff while you're not around.
I change my no to a solid yes on the above. ;)
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I'm pretty sure Peter is describing some baselining for 'standardization' of a single coffee.
I think John's answer will then be 'yes'.
:)
I almost said that if I understand his question it's not any different than measuring in grams.
And yes, I am in agreement with the use of these tools for standardization.
I just don't have any personal need for standardization at this point in time. If I had a shop with teenagers running it and wanted to have a measure for general standards like what I think the Gold Cup was about then yeah, I might use it for that.
Standardization of what and why? Coffee tastes much different the day after roasting than it does two-weeks after. It's also been my experience that the amount of coffee it takes to achieve a good tasting cup of coffee varies with each day of staling, so what good does it do to know what concentration it took yesterday? I suppose if one roasted only one coffee each years that might be useful to know - if one standardized every other factor.
Wait, I heard Orwell wrote a book about standardization; maybe all our questions can be answered there? Is 1984 still considered a futuristic book?
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Standardization of what and why?
Exactly.
I suppose you would have to dial it in every day and come up with a measure. Just like any q.c. on production you would have to test samples at various times during the day to make sure nothing was moving on you.
Then tomorrow do the same thing.
That's how I think it would be used.
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Tex roasting one coffee over the years really won't work either, as the coffee's themselves change from crop to crop.
There are too many variables to really have a 'standard'.
Measure it with a micrometer / mark it with chalk and cut it with an axe.
Aaron
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Tex roasting one coffee over the years really won't work either, as the coffee's themselves change from crop to crop.
There are too many variables to really have a 'standard'.
Measure it with a micrometer / mark it with chalk and cut it with an axe.
Aaron
I matriculated at the, "If you can't dazzle 'em with brilliance then baffle 'em with bullshit.", school of process engineering, so I recognize it when I see it.
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I have used this for a while, and in my experience the measurements didn't really fluctuate as much with the coffee type/age/roast as much as it did with the brewing type, water:coffee, grind, brew time.
<jumps on soapbox>
Using a Scace device didn't really subtract from the art of espresso, or phone back to big brother when someone goes outside the parameters. SO espresso shots outside the Illy parameters are still espresso, nobody gets hurt knowing where the lines in the sand are. The amount of coffee to water ratio before brewing is obviously important, why not the coffee to water ratio when you drink it?
<falls off soapbox>
Check it out, join the travel loop, curiosity only costs postage to the next destination. Skeptics especially welcome.
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Speaking as a former analytical chemist, I am unsure how measuring the TDS correlates with the subjective sense of taste. Your preferred coffee concentration may not be my preferred coffee concentration.
As a non chemist coffee fool I've been saying the same thing from the first time I ever heard about using TDS meters and refractometers with coffee.
Knowing how many PPM of random solids are in a cup does not tell me what they taste like. I see the usefulness for standardization but that is about all.
But, if someone has the same coffee, ground at the same coarseness, and the same water, can't they bracket their brew ratios, checking the PPM/brix of each one until they find a ratio that tastes 'right' and then use that ratio going forward and check with the gadget in subsequent days to see if the ratio is holding true?
How's that for a run-on sentence, complete with commas and apostrophes? Jeffo should comment now. ;)
Longest sentence ever which is longer than my long sentences and I'm also trying to use more commas.
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Using a Scace device didn't really subtract from the art of espresso, or phone back to big brother when someone goes outside the parameters.
Blahahahahaha!
;D
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Tex roasting one coffee over the years really won't work either, as the coffee's themselves change from crop to crop.
There are too many variables to really have a 'standard'.
Measure it with a micrometer / mark it with chalk and cut it with an axe.
Aaron
I matriculated at the, "If you can't dazzle 'em with brilliance then baffle 'em with bullshit.", school of process engineering, so I recognize it when I see it.
Your quote should read, "If I can't understand it or agree with it, then I'll just call it bullshit."
>:D
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But, if someone has the same coffee, ground at the same coarseness, and the same water, can't they bracket their brew ratios, checking the PPM/brix of each one until they find a ratio that tastes 'right' and then use that ratio going forward and check with the gadget in subsequent days to see if the ratio is holding true?
That is why Ryan uses the TDS meter in his shop. He expressed it, "I would like to make sure we are putting out a consistent product." No commas.
At this point, I am afraid to put any "1st Look" notes up on this thread. Yikes, in anticipating tomatoes from the onlookers <stubborn smile>.
B|Java
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Longest sentence ever which is longer than my long sentences and I'm also trying to use more commas.
No, St. Paul has Peter beat by a mile. And one of two makes sense.
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That is why Ryan uses the TDS meter in his shop. He expressed it, "I would like to make sure we are putting out a consistent product."
Makes sense.
At this point, I am afraid to put any "1st Look" notes up on this thread. Yikes, in anticipating tomatoes from the onlookers <stubborn smile>.
Your firsthand experience should carry more weight than guesswork.....I'm guessing. ;)
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At this point, I am afraid to put any "1st Look" notes up on this thread. Yikes, in anticipating tomatoes from the onlookers <stubborn smile>.
Your firsthand experience should carry more weight than guesswork.....I'm guessing. ;)
Man, I could even smell the oregano in the sauce that would be coming my way...
B|Java
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Man, I could even smell the oregano in the sauce that would be coming my way..
Well....
Does anybody past coffee year #1 have a desire to "put out a consistent product" in the kitchen for their personal consumption?
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Man, I could even smell the oregano in the sauce that would be coming my way..
Well....
Does anybody past coffee year #1 have a desire to "put out a consistent product" in the kitchen for their personal consumption?
Maybe I missed the point here, but I would think a lot of people would be guilty of this. Anybody with a PID on their espresso machine, or that weighs coffee and/or water before brewing, that does a water dance, or uses a timer to control brewing variables is interested in consistency.
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Maybe I missed the point here, but I would think a lot of people would be guilty of this. Anybody with a PID on their espresso machine, or that weighs coffee and/or water before brewing, that does a water dance, or uses a timer to control brewing variables is interested in consistency.
I see your point..
I'm not advocating using no units of measure and swinging wildly every time you step up to the beans.
I'm saying that the point of dialing down to the level of total dissolved solids and brix (the way I see it) is ultimately only going to be useful to lock down an exact measure for standardization.. Producing the same cup predictably with repeatability.
I like the PID to lock down the variable of temp so I am within spec but that is a far cry from locking down the TDS, brix, and producing the SAME shot over and over. See what I'm saying? While I want to remain in a predictable temp zone the last thing I want is to produce the same shot over and over...
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You may be overestimating the effectiveness of this device, I highly doubt it will make your (or any other GCBC member) coffee brewing too controllable and predictable.
Join the travel loop and try it. Resistance is futile.
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I'll decide after the Bl java first look review.
;D
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I'll decide after the Bl java first look review.
;D
I don't expect it to do anything except quench or further stretch my curiosity -- have a terrible dose of those on most things I don't understand.
B|Java
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yakster,
Although it was hard to use, could you get meaningful readings with your floating hydrometer? For example, could you see a difference in say a TDS of 1.2 versus 1.3?
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Hydrometer...
:-X
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Thanks yakster, the hydrometer walk-through and pictures are great!
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Yes thanks yakster, it would be nice if there was a hydrometer that was spread out just over the brewed coffee range.
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What does measuring the gravity of the coffee tell you......the gravity of course but how does that correlate to something you are trying to find out?
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Specific gravity is just a fancy way of saying density compared to water. Just another way of sneaking up on how much brown stuff actually made it into the cup.
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Specific gravity is just a fancy way of saying density compared to water. Just another way of sneaking up on how much brown stuff actually made it into the cup.
Yeah..... isn't it odd to move from such fine measures like TDS and brix to very crude measures like gravity?
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...
TDS is 85% of Brix, use this extraction chart ([url]http://www.bunnomatic.com/pages/coffeebasics/cb4technique.html[/url]) as a guideline as to what the tds "should" be for your coffee:water ratio. Note how the 19:1 ratio has the biggest window of "acceptable" tds values. Please don't let this dogma blind you ...
<Hand raised>
So, brewed a vacpot of Dominican Corazon de Oro. 68 grams to 42 oz water. TDS came back 122 at room temp with the refractometer at 1.20. When I am looking at Bunn's (SCAA) chart, I am not sure what I am reading.
Is the chart measuring refraction or TDS?
...and yes, it was a very good cup (primary measurement).
B|Java
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...
TDS is 85% of Brix, use this extraction chart ([url]http://www.bunnomatic.com/pages/coffeebasics/cb4technique.html[/url]) as a guideline as to what the tds "should" be for your coffee:water ratio. Note how the 19:1 ratio has the biggest window of "acceptable" tds values. Please don't let this dogma blind you ...
<Hand raised>
So, brewed a vacpot of Dominican Corazon de Oro. 68 grams to 42 oz water. TDS came back 122 at room temp with the refractometer at 1.20. When I am looking at Bunn's (SCAA) chart, I am not sure what I am reading.
Is the chart measuring refraction or TDS?
...and yes, it was a very good cup (primary measurement).
B|Java
The chart is showing TDS, you get your water:coffee ratio and plot it against TDS solving for extraction rate.
So (42oz * 30g/oz)/68g gives you a nice 18.5 ratio, which is pretty much the middle band. The middle band gives the most area in the "ideal" box. I tend to dose at a lower ratio, (more coffee) I use the higher bands and have a narrower "ideal" window.
TDS measuring 1220 would put you right in middle of the box. The refractometer reads in Brix, which correlates to TDS/850. If I multiply 1.20 * 850 I get 1020, which puts you lower left of ideal.
The Bunn chart recommends you will get an even better cup if you grind a little finer, or brew a little longer. Although it is interesting to see what their recommended cup tastes like, the meter can also indicate how consistent your brew method is in terms of strength, and your general preferences vs their "research".
Also interesting to test local coffee shops, compare against same technique/coffee/dose on a friends grinder, etc.
One thing I forgot to mention:
The refractometer can be calibrated by using distilled water. The line should go to zero, the scale is adjustable with the set screw on top. The unit will read strangely if the prism and the fluid measured are at different temperatures, and will always read weak if the coffee is warm at all.
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I read through the post and can't find a 2nd taker. Is there one in the house?
My experience.
1) I think the refractometer needs distilled water for re-calibration. My readings were off in comparison to the .85 x TDS.
2) I have read too much on this, TDS vs Brix, trying to find an entry point. I will stop here.
In all seriousness, I don't have the background to understand the food chemistry involved -- the TDS meter, let alone compare it to a refractormeter. I gave it the old college try but came away merely confused. Thread at http://www.coffeed.com/viewtopic.php?f=17&t=2489 (http://www.coffeed.com/viewtopic.php?f=17&t=2489) has some good reading, it only I could latch onto it.
As kids, we actually played with mercury (before we knew the toxicity) and would keep it in a vial, adding to it whenever we dropped a glass thermometer. We used to push it around on a glass table, always trying to pick it up. Impossible. Getting my mind around TDS and refraction has taken me back to "picking up mercury."
Who is next?
B|Java
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Just curious, what reading did you get on the refractometer (the value)?
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Just curious, what reading did you get on the refractometer (the value)?
123 on TDS
120 on refractometer
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118 on TDS
117? on refractomer (increments are tiny and my eyes are not good)
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123 on TDS
120 on refractometer
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118 on TDS
117? on refractomer (increments are tiny and my eyes are not good)
Can you imagine if you got 142 and 109.... or even 117 and 117. :-X
;D ;D
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Can you imagine if you got 142 and 109.... or even 117 and 117. :-X
;D ;D
Yes I can. You must have been in my chemistry class.
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I hope I haven't muddied the water too much already, but can't resist risking adding further mud to the mix with one more try...
Espresso it is easy to see when you are under or over extracting a shot, and it is easy to taste the consequences. Not everyone agrees as to the perfect extraction ratio, but we can talk about ristrettos, overloading, letting shots go long, etc. Adding water to it for an americano doesn't change the extraction rate, but does change the strength. Extraction rate and strength are obviously different.
In brewed coffee things are much harder. Without measuring everything, and then dehydrating the remaining grounds to get the final amount of mass that got extracted, (and hopefully went into the coffee) it is very hard to figure out how the extraction went.
The refractometer is just a way to back into this observation of the extraction, but we have to know the water:ratio to use the TDS shortcut since we measure the destination (in the cup) rather than the source. (in the grounds) Although it doesn't read TDS directly, the refractometer may be a better path to TDS in terms of accuracy than the conductivity meter you have that reports TDS directly. I know the SCAA recommends conductivity meters for TDS, but it might be screwing you up more than helping.
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Was the 120 refractometer reading like the picture below with the blue/white intersection down at the red line?
If so the %TDS was .85 times 1.2 or 1.02% (on the weak side).
(http://mnlakecams.com/refrac.jpg)
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Thanks for the image GT! The meter we have is inverse, the blue covers the lower part of the scale. The example below would read 5.3 (the red line I think was added by GT to illustrate the reported reading)
The consistency of B|labPartners readings is pretty good. I aim for readings in the 1.4 - 1.5 range on the refractometer, but I do like brewed coffee strong. If my tastes didn't coincide with the Bunn chart, I'm sure I would change my palette (not!)
Just to make sure it wasn't knocked around too much in the mail, it might be interesting to take a reading from tap water. My city water tested really close to 0.0. Again, testing to a certain value is interesting, but mainly I use it to compare brewing methods, grinder changes, trying to improve the crap office drip, etc.
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Just to make sure it wasn't knocked around too much in the mail, it might be interesting to take a reading from tap water. My city water tested really close to 0.0....
I just ran this and tap water ran just a hair below 0.0.
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Bump, last chance for the quantitatively curious! Try it, maybe your coffee will like it!
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Refractometer is headed back to Hoosierville. No March madness this year, http://espn.go.com/mens-college-basketball/team/_/id/84/indiana-hoosiers. (http://espn.go.com/mens-college-basketball/team/_/id/84/indiana-hoosiers.)
B|Java
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I guess the old optical refractometer and the table just don't have the appeal of the ExtractMojo setup.
Maybe if I mount a slide rule on it... 8)
Us hoosiers hedge our bets, we still have Notre Dame, Purdue, and Butler in!