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Measuring Coffee Strength With A Brix Meter
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Enkerli
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Posted Wed Aug 16, 2006, 8:29am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

treston Said:

What do people think of hydrometers? this would be my preferred way of measuring, though you do need a certain amount of liquid for it to float in.

Posted August 16, 2006 link

Well, that's probably the main issue, at least for espresso. Precise hydrometers need quite a bit more than an espresso's worth of liquid.


What nobody has mentioned is density of the water, i.e. 1 litre of water @ 100C when cool will have a lower volume by about 3%. People are usually cooling for these TDS readings so the results are higher than if it was still hot.

At least in beer brewing, this is one of the main reasons to use a refractometer instead of a hydrometer. Not that temperature has no influence but since the volume of liquid is minuscule, it cools off very rapidly. Even with hydrometers, there are conversion tables to account for temperature (it's not a linear function).

 
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treston
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Posted Fri Dec 8, 2006, 6:49am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

sorry for the very delayed replies!

Enkerli Said:

Well, that's probably the main issue, at least for espresso. Precise hydrometers need quite a bit more than an espresso's worth of liquid.

Posted August 16, 2006 link

Yes I got a hydrometer and it is very large, the bulb is huge on it and the reading stem is extremely narrow, pretty useless for espressos, more suited to bulk brewing (which I am more interested in).

Enkerli Said:

At least in beer brewing, this is one of the main reasons to use a refractometer instead of a hydrometer. Not that temperature has no influence but since the volume of liquid is minuscule, it cools off very rapidly. Even with hydrometers, there are conversion tables to account for temperature (it's not a linear function).

Posted August 16, 2006 link

Yes it will cool quickly on the refractometer which is an advantage. My real question is more the fact that people will say "I want my coffee to have a TDS of 1.4" but do they mean when it is hot? or when cool? I would presume cool since that is the reading most end up taking and comparing. Some TDS readers have automatic temperature adjustment. I find this is not great at all. I now allow all my samples to cool to the same temperature overnight in sealed containers, the TDS readings are far more stable.

I was recently doing tests comparing the theoretical volume of a tank to measured results. My theoretical tank held 20.5L, but was almost 1 litre more when measured. The problem was it filled to a certain level probe with cold water, then expanded by 4% giving me a higher volume when heated, in a different electronics setting the tank will stagger the filling so water is always hot, in which case I do get 20.5L. Hot and cold TDS readings will be off by 4% for the same reason.
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Enkerli
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Enkerli
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Posted Fri Dec 8, 2006, 8:16am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

Oh! Bulk brewing... Interesting.
18l to 23l is a common batch size for beer and we do use hydrometers. We do know about the volume differences. Automatic correction could be convenient but you do end up with measurements which aren't completely accurate. The thing, though, is that if you're comparing values from the same device at the same settings, you may not get a perfect picture but you're getting relevant data. We do want to be as precise as possible, but there are a few "fudge factors"...
I think the point about grounds to water ratio and a kind of coefficient to get a given Brix/Gravity/TDS value is more interesting than those actual values. The experiment seems to have been to compare Aerobie's AeroPress to other brewing methods and this coefficient is an interesting piece of data. But I doubt it'll ever become an actual measure of anything very specific.

 
Alex
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treston
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Posted Fri Dec 8, 2006, 10:29am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

Enkerli Said:

Oh! Bulk brewing... Interesting.
18l to 23l is a common batch size for beer and we do use hydrometers.

Posted December 8, 2006 link

That is interesting, would you consider it more accurate? I would have imagined commercial beer producer would have to be very exact since excise duty would be based on the %.

Enkerli Said:

The thing, though, is that if you're comparing values from the same device at the same settings, you may not get a perfect picture but you're getting relevant data.

Posted December 8, 2006 link

This is very true, like people weighing themselves on different cheap scales each week and getting hugely different readings! doesnt matter what the figure says, is it more or less than last week, thats all that matters.
I have customers send me bottles with samples of brewed coffee in the mail asking me to determine settings for machines to give the equivalent brew. In that case you are spot on, it doesnt matter what factor I am out by, dont even need the 0.85 conversion factor, I just need to match to readings.

I was just wondering if it is usually hot or cold. One case where it does matter to be accurate is acheiving certain guidelines, like the "gold cup" and attaining brews which fall within certain parameters such as brewing charts like this
Click Here (www.bunnomatic.com)
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Enkerli
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Enkerli
Joined: 1 Aug 2004
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Location: Montreal, Qc
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Espresso: (At cafés, not at home)
Grinder: Hario hand grinders
Vac Pot: (Moka Pot) Bialetti Brikka
Drip: Steep and release pour-over
Roaster: iRoast-2
Posted Fri Dec 8, 2006, 12:49pm
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

The few commercial beer brewers I know do use hydrometers and it seems that a Brix/refractometer is more a matter of convenience than actual precision for beer brewing. One issue with beer is that refractometer results are skewed by the presence of alcohol, which is not the case with hydrometers. Since the percentage of alcohol is precisely what we're trying to calculate, that's a major issue. There are conversion formulas around (if you have the original gravity before fermentation, you can calculate out the effect of alcohol on the final gravity reading), but either pros don't trust them or the precision of a refracto- or Brix meter isn't sufficient for their uses.
Of course, with large quantities, people use large hydrometers, which are indeed quite precise.

As for reasons for precision and standards... I personally understand the reasoning, especially from the "engineering" side of coffee (or beer) brewing. But, as many CGers would surely agree, coffee quality is very difficult to measure indeed. As we all know, a 25s espresso with a thick crema can be perfectly unpalatable even if it looks perfect while a 15s espresso with little crema can be a thing of beauty. In fact, two baristas can pull shots on the same machine with the same parameters and get quite different results in flavour even if the shot took the same amount of time.

Another way to look at this is that in the story told by Bunn's chart (apart from the fact that it's based on the law of averages) is a fair bit of leeway. From 1.15% TDS to 1.35% TDS, a number of things can happen. It might well be the ideal range is much narrower but that this chart accounts for some discrepancies in measurements.

No idea who can answer your question. But asking the SCAA (or Bunn) directly should be interesting. If their "standard" is so reliable, they surely have documentation on the way to measure TDS. In fact, they really should say which calibration they use for the hydrometer "brew strength meter."

But, again, if you always measure brews with samples brought back to calibration temperature, you always use the same hydrometer that you have calibrated with this funnily-named "golden cup" SCAA "standard," and you get consistent results in your adjustments, you've achieved more than this kind of chart covers.

Thanks for the edifying link!

 
Alex
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CoffeeRoastersClub
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Posted Fri Dec 8, 2006, 1:10pm
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

AlanAdler Said:

Do you enjoy tinkering with grinding and brewing techniques?   Do you have about $270 to blow on your coffee hobby?   If not, this isnít for you.   But if so, read on.
...snip...
As I said in the beginning, Brix isnít for the casual barista.   But if youíre a Mark Prince, or Barry Jarrett or David Schomer, after you try Brix youíll wonder how you ever got along without it.

Posted January 16, 2006 link

Alan,

Have you ever done a Brix on a typical French Press? I would be interested in knowing that.  I drink French Press all the time.

Len
CoffeeRoastersClub.com

 
"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674

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rasqual
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Posted Sat Dec 9, 2006, 11:01am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

AlanAdler Said:

The SCAA recommends 1.25 percent TDS for ordinary brewed coffee.   That corresponds to 1.47 Brix, which the meter rounds to 1.5

Posted January 16, 2006 link

Despite my interest in Brix, my huge, huge problem as I rub my chin about this is the narrow range of measurements refractometers are forced to deal with -- refractometers that just aren't going to be able to measure a difference easily detectable by the palate.

I looked into the Atago PAL-10S Urine Refractometer, which has a range of 1.000 to 1.060 SG. I thought that might be better resolution, but when one converts to Brix it's evident that despite its narrow range (0 - ~15 Brix, converted) its resolution is actually coarser.   :-\

I'm despairing. If all I care about is accuracy in the range of 1.2 to 2.2 Brix, I only have 10 points to play with.

Then, lo, the acccuracy is +- 0.2

=8-0
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treston
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Posted Mon Dec 11, 2006, 5:24am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

Enkerli Said:

The few commercial beer brewers I know do use hydrometers and it seems that a Brix/refractometer is more a matter of convenience than actual precision for beer brewing.  

Posted December 8, 2006 link

Yes, they are very handy, pocket size and easy to read, and only a few drops needed.

Enkerli Said:

There are conversion formulas around (if you have the original gravity before fermentation, you can calculate out the effect of alcohol on the final gravity reading), but either pros don't trust them or the precision of a refracto- or Brix meter isn't sufficient for their uses.

Posted December 8, 2006 link

Hydrometers for homebrewers often have a few scales, one of which is "potential alcohol". This is only an estimate, if you have 2 brews of the exact same starting SG and exact same finishing SG they can have different alcohol contents. The yeast mainly produces 3 things, more yeast, alcohol and carbon dioxide, depending on factors such as oxygenation you can get different ratios of alcohol to CO2 being produced, obviously brewers prefer alcohol. Vinometers are also used by homebrewers to estimate wine %, these require the wine to be totally dry and work using capillary action and depend on the wines SG. I suppose the only real way is to completely distil the beer and measure the distillates SG.

When diluting spirits a strange thing happens. If you add 1 litre of 50% spirits to 1 litre of distilled water you would expect to get 2 litres of 25% spirit, but actually you end up with a bit less than 2L, and it is not 25% (can't remember if it is more or less).

Another TDS measurement method is oven drying, some claiming it is the best way but you also end up with any undissolved solids in the coffee, unless it was properly filtered.

Enkerli Said:

No idea who can answer your question. But asking the SCAA (or Bunn) directly should be interesting. If their "standard" is so reliable, they surely have documentation on the way to measure TDS. In fact, they really should say which calibration they use for the hydrometer "brew strength meter."

Posted December 8, 2006 link

I shall ask them. I have some information from testers in Norway with definitions of some terms like "contact time", "brewing time" etc some of which surprised me. In europe the desired range on that chart is shifted upwards. As you say the chart cannot tell you if it tastes nice, it could be quite poor but in range. It is still probably the easiest way for comparing machines and coffee from the engineering side.
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gt
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Posted Wed Jul 4, 2007, 8:43am
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

I recently purchased this analog Brix meter ($39) and find it very repeatable and easy to use.

http://tinyurl.com/2mct9x

Assuming the Brix readings I get are accurate, Iím wondering if the following is correct:

When I make coffee in my Newco OCS-8 I use 48 oz of input water and  2.0 oz of coffee, I get a Brix reading of 1.5 which I believe gives close to the desired 1.25% TDS (.85 times 1.5) but I believe the extraction is 30% based on this:  

.0125(48oz) = .6oz and 0.6oz/2.0oz = 30%

If this is correct, how would I adjust things to maintain the 1.5 Brix reading but get to 20 % extraction?

Thanks gt
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gt
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Joined: 29 Jan 2007
Posts: 210
Location: Mpls/St Paul MN
Expertise: I like coffee

Espresso: None
Grinder: Virtuoso
Drip: Cones & CCD
Roaster: P1 w/ variacs
Posted Wed Jul 4, 2007, 2:15pm
Subject: Re: Measuring Coffee Strength With A Brix Meter
 

I think I can answer my own question now.

  1. If I use 48 oz. of input water and want 1.25% TDS, I need 0.6 oz of coffee dissolved in the input water (0.0125 times 48  = .6)

  2. To get 20% extraction, I need to use 3 oz. of coffee (0.2 times 3 = .6).

So I think I should use 3 ounces of coffee and adjust my grind until the resulting coffee is 1.5 Brix.

gt
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