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jpender
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jpender
Joined: 11 Jul 2011
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Location: California
Expertise: I like coffee

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Posted Wed Mar 5, 2014, 5:49pm
Subject: Re: Coffee ratios
 

MWJB Said:

You say that the extraction yield target relates to drip coffee. Why do you say that specifically? The brew ratio advocated by the CBI/CBC was suggested with regards to popular brewers of the day. It works for drip & other methods, as long as they adhere to certain parameters (even drip doesn't always). You can get fairly close to an accurate reading by emulating exactly the methods & masses suggested by SCAA/SCAE. From the measurements & ratios in my previous post, you can see approx +/-1g/l swing depending on units used...measuring to the decimal point of an ext. yield doesn't seem to have been a priority, it seems more about just getting in the box as a whole, an everyday guide for industry & home?

The target yield range still stands after all these years (unless you have an EK43, even without one certain folk/tastes advocate specific yield ranges within the box as more desirable than others, some folk have preference/do not reject yields just outside the lower limit), but the research was done by other agencies then adopted by/supplied to Lockhart, I guess he concurred with it, otherwise we'd have a different chart.

The CBI/CBC advice isn't necesarilly, or always, an "error", it mostly follows the method/protocols that they used then. Today with more attention paid to precise measurement and narrowing down the super ideal ranges wthin that ideal range, different brewers & protocols, the chart needs re-jigging in a lot of cases. Vince's contribution isn't a mere reworking, or confirmation of Lockhart's work, it's significant stride forward from that.

It's not clear to me whether Lockhart was responsible for the brew ratio protocol that they adhered to, or whether he inherited it from the studies actually carried out by the National Coffee Asociation, or Midwest Research Institute, both of which the CBI/CBC used for their chart(s). Vince would probably know better than me? The CBI/CBC also appeared to be busy with educating the public as to best practices in brewing (re. time & grind) & assessing products brough to market, to ensure that they conformed to a standard.

Again, much of this is particularly relevant to accurate measurement & assessment. If you're brewiing by taste & not trying to specifically hit a pre determined target, +/- a couple of g/l isn't going to make or break.

Posted March 5, 2014 link


Why drip? Because that's what I remember Vince saying in his talk. It's also in the accompanying slides. But it doesn't really matter for the question I'm asking.

You seem well primed to answer a different question. It's clear you have a depth of knowledge and experience on that subject that I lack. It reminds me of my high school AP American History test. At the time I knew the subject very well but the essay question I got was one I didn't know how to answer. So I answered a different, but related, question that I could write quite a bit about. At the end of the essay I apologized for not answering the actual question. They gave me a 5.

I give you a 5, MWJB, even though you didn't answer my question.

I wanted to know about the specific change in target extraction that Vince claimed was due to the variation in the density of water with temperature. This isn't about brewing method, grinder model, personal preference or any of the other numerous brewing variables. It's simply a question of how exactly did Lockhart fail to account for a basic property of chemistry in his work.

From a previous post I thought you probably knew the answer but for some reason felt compelled to keep it secret. But now I think it's far more likely that you don't know, which is okay with me. The original work isn't easy to obtain. As you said, Vince would know. But I'm not going to hold my breath waiting for him to post a response here.
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jpender
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jpender
Joined: 11 Jul 2011
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Location: California
Expertise: I like coffee

Grinder: OE LIDO
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Posted Wed Mar 5, 2014, 5:51pm
Subject: Re: Coffee ratios
 

I searched a little and found a document written by Lockhart for the CBC in 1969: "Coffee Solubles and Beverage Acceptance". In it he describes a method for determining the extraction. It looks fine except that he doesn't mention the temperature of the beverage when the volume is measured. And his conversion factor (134 oz/gal) only works if the coffee is cool. If it were hot it would be closer to 128 oz/gal. So maybe this is the error? Or maybe not. His procedure also suggests simply using a brew chart where initial brew water is measured instead of the beverage (along with an assumption of water retention in the grounds). The devil is in the details to which I don't have access.

Also, that wasn't the original research. It's a pamphlet for non-scientist industry professionals. So it's possible that Niven, et. al., whom he cites as the source of the 18-22% range, actually did correctly adjust for density variation. Or maybe not.

Along the way I learned that Lockhart was a polar explorer of sorts, having accompanyed Byrd in 1939. There's even a mountain in Antarctica named for him! That wasn't the question either but I liked that particular answer.
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MWJB
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Posted Thu Mar 6, 2014, 1:41am
Subject: Re: Coffee ratios
 

jpender Said:

Why drip? Because that's what I remember Vince saying in his talk. It's also in the accompanying slides. But it doesn't really matter for the question I'm asking.

You seem well primed to answer a different question. It's clear you have a depth of knowledge and experience on that subject that I lack. It reminds me of my high school AP American History test. At the time I knew the subject very well but the essay question I got was one I didn't know how to answer. So I answered a different, but related, question that I could write quite a bit about. At the end of the essay I apologized for not answering the actual question. They gave me a 5.

I give you a 5, MWJB, even though you didn't answer my question.

I wanted to know about the specific change in target extraction that Vince claimed was due to the variation in the density of water with temperature. This isn't about brewing method, grinder model, personal preference or any of the other numerous brewing variables. It's simply a question of how exactly did Lockhart fail to account for a basic property of chemistry in his work.

From a previous post I thought you probably knew the answer but for some reason felt compelled to keep it secret. But now I think it's far more likely that you don't know, which is okay with me. The original work isn't easy to obtain. As you said, Vince would know. But I'm not going to hold my breath waiting for him to post a response here.

Posted March 5, 2014 link

Ha ha, I'll take a "5". You are slightly misunderstanding, or reading too much into the concept that Vince was alluding to, it's pertinent to the chart as a whole, rather than the yield target box range specifically. I know that you are pretty clued up on extraction yield analysis, I was hoping subtle would be enough for you to identify the mechanism. To establish the yield from the paper brew ratio chart means an implied beverage mass, if you are changing the mass of the water added, or changing brewer/method it follows that the beverage mass may be changed also. If you have a different amount of beverage at a prescribed %TDS, then you have extracted a different % from the grinds. That's how the yield shifts in relation to the chart...in the real world brewing often doesn't adhere to the charts parameters, there's a degree of rule of thumb involved. Vince's method, which is proprietry (& not suitable for in depth analysis/breakdown here), is measurement based, rather than relying on implied parameters.

The temperature of beverage samples may vary depending on measurement method used, CBI/CBC could have used 2 different methods, but for the samples to be meaningful it's likely they correlate to lowest common denominator. They probably didn't anticipate the need for super precise yield figures, so beating themselves up over sample temp, within a few 10's of C, is likely moot. Lockhart didn't "fail", per se, he started from a different point, assumed a fixed scenario & used tools at his disposal. If he even established the range/protocol at all...the CBI themselves didn't carry out the research, we can only speculate on whether they were involved in the design/methodology, or even if it was within their remit. I don't see why it would need to be, as the broad targets & fixed assumptions make for simple calculations which you can find in lots of brewing literature over the last 60yrs.

In many aspects of life things may be reduced to a "diagnostic state", as a datum for reference, that does not necessarily relate to real-world scenarios & actual measurement/practical use, the paper charts strike me as closer to the former & Vince's method the latter.
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MWJB
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Posted Thu Mar 6, 2014, 3:11am
Subject: Re: Coffee ratios
 

jpender Said:

Why drip? Because that's what I remember Vince saying in his talk. It's also in the accompanying slides. But it doesn't really matter for the question I'm asking.

Posted March 5, 2014 link

Note also that in the same talk, Vince shared the concept of immersion yield which was not acknowledged/identified when the charts were established.
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jpender
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jpender
Joined: 11 Jul 2011
Posts: 719
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Thu Mar 6, 2014, 12:25pm
Subject: Re: Coffee ratios
 

MWJB Said:

You are slightly misunderstanding, or reading too much into the concept that Vince was alluding to, it's pertinent to the chart as a whole, rather than the yield target box range specifically. I know that you are pretty clued up on extraction yield analysis, I was hoping subtle would be enough for you to identify the mechanism. To establish the yield from the paper brew ratio chart means an implied beverage mass, if you are changing the mass of the water added, or changing brewer/method it follows that the beverage mass may be changed also. If you have a different amount of beverage at a prescribed %TDS, then you have extracted a different % from the grinds. That's how the yield shifts in relation to the chart...in the real world brewing often doesn't adhere to the charts parameters, there's a degree of rule of thumb involved. Vince's method, which is proprietry (& not suitable for in depth analysis/breakdown here), is measurement based, rather than relying on implied parameters.

Posted March 6, 2014 link

I may be missing something but this isn't it. You aren't telling me anything I don't already know.

MWJB Said:

The temperature of beverage samples may vary depending on measurement method used, CBI/CBC could have used 2 different methods, but for the samples to be meaningful it's likely they correlate to lowest common denominator.

Posted March 6, 2014 link

These are just speculations.

MWJB Said:

They probably didn't anticipate the need for super precise yield figures, so beating themselves up over sample temp, within a few 10's of C, is likely moot.

Posted March 6, 2014 link

In that CBC document Lockhart took pains to establish the precision of his coffee strength measurement of 1.396% which led to a calculated extraction of 19.7%. So apparently he had some interest in being precise. A few tens of degrees Celsius would alter the calculated extraction by 0.2-0.4%. That's more than the effect due to Lockhart's estimated error in the coffee strength.

Anyway, Vince was talking about a difference of about 80C.
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MWJB
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Posted Thu Mar 6, 2014, 1:47pm
Subject: Re: Coffee ratios
 

jpender Said:

I may be missing something but this isn't it. You aren't telling me anything I don't already know.

Posted March 6, 2014 link

Probably very true. What do you expect? Me to draw you a chart? ;-)

jpender Said:

These are just speculations.

Posted March 6, 2014 link

No, CBC literature mentions one method for sure, it has a temperature protocol.

jpender Said:

In that CBC document Lockhart took pains to establish the precision of his coffee strength measurement of 1.396% which led to a calculated extraction of 19.7%. So apparently he had some interest in being precise. A few tens of degrees Celsius would alter the calculated extraction calculation by 0.2-0.4%. That's more than the effect due to Lockhart's estimated error in the coffee strength.

Posted March 6, 2014 link

Your questions revolved around the paper chart from the 50's, if you can identify 1.396%TDS on the chart you must have a very big copy. :-)

jpender Said:

Anyway, Vince was talking about a difference of about 80C.

Posted March 6, 2014 link

Wrong end of the stick.
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jpender
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jpender
Joined: 11 Jul 2011
Posts: 719
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Thu Mar 6, 2014, 6:13pm
Subject: Re: Coffee ratios
 

MWJB Said:

What do you expect? Me to draw you a chart? ;-)

Posted March 6, 2014 link

I was hoping for a straight answer.
But at this point I expect more of the same.

Cheers!
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MWJB
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Posted Fri Mar 7, 2014, 1:28am
Subject: Re: Coffee ratios
 

jpender Said:

I was hoping for a straight answer.
But at this point I expect more of the same.

Cheers!

Posted March 6, 2014 link

What you originally asked is how did Lockhart make "schoolboy" errors, he didn't.

What you appear to want is for me to give you a public, blow by blow, breakdown/conversion of the perceived discrepancies between 2 methods, one subject to legal protection. Goading isn't going to force my hand there.

You are playing both ends against the middle - on one hand Lockhart was making schoolboy errors, but you have documentation from CBC outlining calculations of super accurate TDS measurements & a yield (not impossible depending on method, but adding extra decimal places doesn't necessarily denote accuracy...I just tried to emulate your described scenario and came up with %TDS to seven decimal places - 1.3958115%, could just as easily have been ten or twenty?). You state how the figures were arrived at, so you know how that was done & can employ the same method. If you're careful you can get "in the box" answers.

If there is anything relevant to the OP, it's be consistent in your weights, measures & ratios.
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jpender
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jpender
Joined: 11 Jul 2011
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Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Sat Mar 8, 2014, 11:41am
Subject: Re: Coffee ratios
 

MM, I apologize for questioning too aggressively. I certainly don't want you to cross a line.

I'm just curious about the history. I've gone through the exercise in order to understand specifically what Mojo does. If there's an explanation there for this question I'm too dumb to see it. So it's a mystery to me and will probably remain so. It has zero bearing on how I make coffee.


For what it's worth, here's an excerpt from that Lockhart article:

TABLE TWO

Weights of Soluble Solids in Ten Replicate Ten Milliliter
Volumes from an Urn of Coffee Beverage

Sample No        Weight of Solid Grams       Soluble Solids %

1                         0.1395                             1.395
2                         0.1392                             1.392
3                         0.1395                             1.395
4                         0.1397                             1.397
5                         0.1397                             1.397
6                         0.1395                             1.395
7                         0.1401                             1.401
8                         0.1393                             1.393
9                         0.1396                             1.396
10                       0.1396                             1.396

Average              0.1396                             1.396

Standard Deviation = 0.0001 | 55/9 = 0.00025

95% confidence limits   = 0.1396 2.228 (0.00025)
                                      = 0.1396 0.0006
                                      = 0.1390 and 0.1402

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MWJB
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Posted Sat Mar 8, 2014, 5:06pm
Subject: Re: Coffee ratios
 

These look like dehydration results. You don't really need to know the starting ratio (though obviously if you brewed it you would know, or also if you knew a reliable figure for retained brew water) to determine extraction yield from these, just the dry coffee mass & beverage mass. As the beverage is described in ml and TDS weight translates directly to %TDS, it makes sense to assume room temp samples? Another method mentioned by Lockhart was hydrometer.

The VST refractometer compensates for sample temperature over a 15-40C range.

What I meant by "lowest common denominator" is that these may all ultimately point to a consistent answer regarding sample %TDS and hydrometer vs dehydration results could be consolidated, if necessary, by the CBI if using both?

I was looking at another report by Lockhart on water quality, I don't have any TDS/yield figures from that one, but ratio discussed was "the usual ratio, 2 level tablespoons per 6oz of cold water", coffee was a "reputable brand, Silex grind, vacuum packed in 1lb tins". Silex 10cup vac pots were used to brew samples, pre-dosed top chamber, 2 min steep plus 1 min draw down. Due to the nominal nature of the dosing, an accurate yield can't be determined.

Mojo corrects for actual brew masses (you can use presets, or input actual, measured parameters), so you don't rely on preset assumptions regarding temps & mass. There's more than one factor at play here that can introduce discrepancies. Not saying that sample temp is entirely irrelevant, just there are bigger fish to fry.
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