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TimothyH
Senior Member
TimothyH
Joined: 9 Sep 2006
Posts: 30
Location: USA
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Posted Mon Sep 20, 2010, 2:29pm
Subject: coffee refractometer
 

According to their claims this won a best new product award at SCCA.  Does anyone know anything about it?  This is not spam, I am not recommending this product.  I just wonder if it would help me improve the quality of my espresso and coffee.

http://vstapps.com/store/coffee-espresso-refractometer/

Thanks,

Tim
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JasonCoffee
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JasonCoffee
Joined: 17 Mar 2009
Posts: 15
Location: Kansas City
Expertise: Professional

Posted Mon Sep 20, 2010, 6:23pm
Subject: Re: coffee refractometer
 

I have been asked about this by a few of my readers also. I am going to see if I can't get my hands on one of these. If I do I will be happy to share my thoughts with you.

 
NEW Coffee Forum: http://coffeecupnews.org/forum
Coffee Reviews: http://coffeecupnews.org
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Chang94598
Senior Member


Joined: 24 Oct 2007
Posts: 213
Location: SF Bay Area
Posted Mon Sep 20, 2010, 8:30pm
Subject: Re: coffee refractometer
 

My personal opinion is that the refractometer would work more advantageously in brewed coffee than espresso. In brewed coffee, there is less solid particle, compared with espresso, to reflect light.  For example, the amount of solid particles in espresso will conceivably be altered by the hole shape of the espresso filter.

On the other hand, due to the small amount of liquid required for refractometer, it is easier to use than conductive TDS meter. But also be mindful, espresso also composes crema, which cannot be measured by refractometer.

I use however a conductive TDS meter for brewed coffee. It is easily available from retailers at fraction of the cost of refractometer. I just calculate the result on my Palm device (yes, I still use the Palm for its simplicity).  It is helpful to read over the SCAA Coffee Brewing Handbook and its concepts, as most of the studies were done many years ago and some of the units are archaic. My discussion on the TDS meter is on HB, if one just wants to use the formula without reading through the book and save some money:

Click Here (www.home-barista.com)

Although there are many conductive meters on the market, make sure to use one which can measure NaCl-unit to at least 2000 ppm.
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lost
Senior Member


Joined: 15 Jan 2008
Posts: 269
Location: Ontario
Expertise: I love coffee

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Posted Fri Sep 24, 2010, 4:26pm
Subject: Re: coffee refractometer
 

Isn't that George Howell's invention ?
He does have an impeccable reputation ?

My question is, would a normal refractometer work ?
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andys
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andys
Joined: 10 May 2003
Posts: 857
Location: NY
Expertise: Just starting

Espresso: Speedster, Londinium 1
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Posted Fri Sep 24, 2010, 5:47pm
Subject: Re: coffee refractometer
 

Chang94598 Said:

My personal opinion is that the refractometer would work more advantageously in brewed coffee than espresso. In brewed coffee, there is less solid particle, compared with espresso, to reflect light.  For example, the amount of solid particles in espresso will conceivably be altered by the hole shape of the espresso filter.

Posted September 20, 2010 link

This is incorrect. Refractometers can be used to accurately measure TDS in espresso if the espresso is filtered before taking the measurement.

Chang94598 Said:

also be mindful, espresso also composes crema, which cannot be measured by refractometer.

Posted September 20, 2010 link

(1) After a short time, crema collapses into the main beverage, so it's not a problem.
(2) The mass of the crema is so small compared to the mass of beverage liquid that measuring it is unimportant.
(3) Are you saying that your meter accurately measures crema TDS?

Chang94598 Said:

I use however a conductive TDS meter for brewed coffee. It is easily available from retailers at fraction of the cost of refractometer.

Posted September 20, 2010 link

The VST refractometer is warranted to be accurate to +/- 0.12% TDS. If you want to get a laugh sometime, call up the manufacturer of your conductivity meter and ask them to guarantee its accuracy when measuring coffee TDS. Perhaps then it won't seem like such a bargain.  :-)

Chang94598 Said:

Although there are many conductive meters on the market, make sure to use one which can measure NaCl-unit to at least 2000 ppm.

Posted September 20, 2010 link

Coffee labs used to struggle with conductivity meters. Since the VST refractometers came on the market, no serious coffee lab continues to rely on conductive meters.

They are inexpensive, however!  :-)

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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andys
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andys
Joined: 10 May 2003
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Posted Fri Sep 24, 2010, 5:58pm
Subject: Re: coffee refractometer
 

lost Said:

Isn't that George Howell's invention ?
He does have an impeccable reputation ?

My question is, would a normal refractometer work ?

Posted September 24, 2010 link

[edited 9-25-10]

The coffee/espresso refractometers and accompanying software were invented and developed by Vince Fedele of VST while VST was a consultant to the George Howell Coffee Company. When Vince left, he retained and or acquired remaining rights to the ExtractMoJo and the Coffee and Espresso refractometers. VST and GHCC made a joint announcement about this last March. So the software and instruments are VST products, not GHCC products.

Last time I checked, George's reputation was still impeccable.  :)

A "normal" refractometer measures "nD", otherwise known as refractive index. nD must be converted into coffee TDS to be useful. The VST refractometers have this conversion built in.

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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Chang94598
Senior Member


Joined: 24 Oct 2007
Posts: 213
Location: SF Bay Area
Posted Fri Sep 24, 2010, 8:49pm
Subject: Re: coffee refractometer
 

andys Said:

This is incorrect. Refractometers can be used to accurately measure TDS in espresso if the espresso is filtered before taking the measurement.

(1) After a short time, crema collapses into the main beverage, so it's not a problem.
(2) The mass of the crema is so small compared to the mass of beverage liquid that measuring it is unimportant.
(3) Are you saying that your meter accurately measures crema TDS?

The VST refractometer is warranted to be accurate to +/- 0.12% TDS. If you want to get a laugh sometime, call up the manufacturer of your conductivity meter and ask them to guarantee its accuracy when measuring coffee TDS. Perhaps then it won't seem like such a bargain.  :-)

Coffee labs used to struggle with conductivity meters. Since the VST refractometers came on the market, no serious coffee lab continues to rely on conductive meters.

They are inexpensive, however!  :-)

Posted September 24, 2010 link

I don't understand espresso enough at the academic level, but I generally don't drink "filtered" espresso. This was my original question about the refractometer. The polyphasic and colloidal feature of espresso "could" make refractometer difficult to apply for espresso. If this device solves this problem, maybe it is well worth the cost.  I always wonder how the other material in espresso contribute to the final refractive index. For example, if only the liquid aliquot is withdrawn, before the crema is settled, will the measurement be different? From my understanding, the formation of the gaseous phase is directly related to the galactomannan and arabinogalactan, which vary from degree of roast and bean variety. The solid cellulose in the espresso brew will also reflect light differently; potentially a planar vs conical grinder will produce different shape particles. The typical espresso brew also contains about 5% of lipid by weight. How much of this lipid is filtered out? What kind of paper? How thick of the filter? How do these factors contribute to the refractive reading, in a typically consumed, unfiltered espresso drink? At least when I was in school, the content in the cuvette cannot contain bubbles, finger prints, solids, etc., and if the measured aliqot is filtered, I am concerned the reading will not reflect the true TDS of espresso.

Where did I say the conductive meter is more or less accurate? Or it measures crema?  My olfactory and taste nerves probably cannot detect a 0.12% difference currently.  The variability in the 5% of lipid that was filtered out alone will contribute more to the margin of error, IMHO.

On a more serious note, what are the problems/struggles encountered by coffee labs with conductive meter? I am a home user who brews mostly one cup at a time.  My municipal water TDS also varies season to season, and this will also contribute my cup TDS.  Knowing the difficulty encountered would be helpful for me to  understand the brewing process better.

:)
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MikeWhite
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MikeWhite
Joined: 21 Jan 2002
Posts: 85
Location: NYC
Expertise: Professional

Posted Sun Sep 26, 2010, 9:13am
Subject: Re: coffee refractometer
 

For what it's worth, I'm a huge fan of the refractometer and MoJo software. I think it's the single most useful tool anyone can have when concerned about consistency and quality. I've written a few posts about my experiences with it here if you're interested.

 
Mike White
NYC
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andys
Senior Member
andys
Joined: 10 May 2003
Posts: 857
Location: NY
Expertise: Just starting

Espresso: Speedster, Londinium 1
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Posted Sun Sep 26, 2010, 11:08am
Subject: Re: coffee refractometer
 

Chang94598 Said:

I generally don't drink "filtered" espresso.

Posted September 24, 2010 link

Nobody said you're supposed to drink filtered espresso. But in using a refractometer, one reserves a few ml of the espresso extraction and filters it in order to get an accurate TDS reading.

Chang94598 Said:

The polyphasic and colloidal feature of espresso "could" make refractometer difficult to apply for espresso....I always wonder how the other material in espresso contribute to the final refractive index. For example, if only the liquid aliquot is withdrawn, before the crema is settled, will the measurement be different? From my understanding, the formation of the gaseous phase is directly related to the galactomannan and arabinogalactan, which vary from degree of roast and bean variety.

Posted September 24, 2010 link

Henry, the basic flavor balance (sour, grassy, sweet, bitter) is related to dissolved solids. Undissolved solids contribute mouthfeel, but little flavor (unless the amount of undissolved solids gets waaay too high). Your concerns about how much crema has collapsed or about the exact quantity of galactomannan may be interesting academically, but have little bearing on flavor balance.

Chang94598 Said:

The solid cellulose in the espresso brew will also reflect light differently...if the measured aliqot is filtered, I am concerned the reading will not reflect the true TDS of espresso

Posted September 24, 2010 link

What you're saying makes absolutely no sense. TDS means Total Dissolved Solids. Filtering out undissolved cellulose has zero effect on dissolved solids.

Chang94598 Said:

The typical espresso brew also contains about 5% of lipid by weight.

Posted September 24, 2010 link

You're not even close. According to Illy, a typical Italian espresso contains 0.25% lipids.

Chang94598 Said:

My municipal water TDS also varies season to season, and this will also contribute my cup TDS.

Posted September 24, 2010 link

Wrong again. The TDS of a brewed coffee averages 13,000 ppm; espresso can be 50,000 ppm - 150,000 ppm. Variations in municipal water TDS of 100-200 ppm are completely swamped by the coffee TDS.

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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EricBNC
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EricBNC
Joined: 22 Jun 2010
Posts: 1,869
Location: North Carolina
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Posted Sun Sep 26, 2010, 1:28pm
Subject: Re: coffee refractometer
 

Decisive rebuttal, well done...

EricBNC: Note.jpg
(Click for larger image)

 
I chew coffee beans with my teeth while gargling with 195 F water to enjoy coffee. What is this "coffee brewing" device you speak of?
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