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.
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.
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:
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.
(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.
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.
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.
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.
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.
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.
MikeWhite Senior Member 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.
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.
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
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.
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.
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