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What I learned on Twitter yesterday about refractometers & bright coffee
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MWJB
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Posted Sat Apr 19, 2014, 11:37am
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

boar_d_laze Said:

It's nice to have quantifiable data about good vs bad coffee.  On the other hand if my coffee tastes bad because it's both bitter and "in your face," I'll dose lower, grind finer, brew cooler, and/or work to a lower brew ratio; and can by God guarantee that tweaking by taste (a) will not only make the espresso taste good, but put it "in the box," too; or (b) if it doesn't put it in the box, that there's something wrong with the box.

Posted April 19, 2014 link

You talk about "the box" as if it's an abstract concept. If you have never identified where you are in the box, or whether you are in it at all, it's a bit of a reach to make assumptions as to its validity? Not that I doubt that you can get in it by trial, error & tasting.

boar_d_laze Said:

While the methodology (any accurate methodology) is too clunky for anyone brewing at a less than industrial volume

Posted April 19, 2014 link



There's nothing that's faster. It takes 60-seconds to make a proper measurement which has the same accuracy and precision (repeatability) as a $20,000 dehydration oven that can take hours and requires strict adherence to laboratory protocol in order to achieve accurate results. The VST refractometer achieves the same accuracy and precision with a single measurement and a few drops of coffee, which you can be tasting and assessing whilst the reading is made.

boar_d_laze Said:

Bottom Line

Taking espresso as an example:  By far the most common problems are diagnosed on the basis of whether the shot is over or under extracted (bitter or sour, respectively); and/or attenuated or "in your face" (too dilute or too concentrated).  Possible causes are limited to roast, technique and/or machine.  

Fixing almost every espresso problem is either a matter of adjusting temperature, grind, and/or dose; or replacing the beans.

Posted April 19, 2014 link

What you have essentially said here is that, problems with espresso relate to being too "attenuated/in your face, diluted/concentrated", ...are down to extraction -you are actually describing a TDS/yield preference.

Adjusting temp, grind, dose...these are mechanisms for varying the extraction yield, that's how they work. Extraction is the thread that ties them together. Replacing the beans, assuming that people are getting nominal, or palatable extractions with them with comparable equipment, is abit of a cop out. If you can only brew with a certain bean/roast level, it's akin to only making salad, because every time you cook you burn the house down, then you blame 'hot food'? You're perfectly entitled to a preference, but if you pull a vile shot with certain beans...aren't you just a little curious about them before throwing them in the trash? If everything that roaster produces is the same, every time it's brewed, how are they still in business?

boar_d_laze Said:

In my experience, there's a limit to how far you can tweak coffee.  For instance, adjusting ~18g doses by the nearest 0.1g isn't going to make a detectable difference in the cup.  Differences which are detectable only as a function of some non-sensory measurement (e.g., %TDS. 1sec difference in pull time, etc.) are only important if they lead to differences which are taste detectable.

Posted April 19, 2014 link

Good example, typically, if your 18g extraction is centre of the box, 0.1g dose either way (same output & consistent prep - all else being equal) equates to +/- ~0.1%Ext Yield...what you are saying is supported by the numbers. It's more likely other factors will have a bigger effect on consistency. Specific enough?

boar_d_laze Said:

If I can pull a great shot dosing at 17g, I don't particularly care if I can pull a similar shot at 19.5g but not through the range of 17.5g - 19g.  Why would I?  I'm after the great shot, not a complete phenomenology of a Las Lajones Natural Caturra roasted C+/FC according to a particular profile and pulled as espresso.  Like nearly everyone else in the universe, if 17g makes a great shot, I'll just keep dosing at 17g, thank you very much.

Posted April 19, 2014 link

The relevance of this paragraph escapes me?

boar_d_laze Said:

I'd love to buy a refractometer because I like toys.  But an accurate refractometer is too expensive to buy on a whim and, sadly, so far no one's supplied a cognizable excuse.

Posted April 19, 2014 link

Sure it's not cheap, not compared to laborious home dehydration, but is it expensive compared to your machine, grinder, roaster? Earlier in this thread you stated, on the subject of roasting, "That better measurement, better software, and a more controllable roaster has allowed me to hit very specific intervals and finishes with greater accuracy and consistency than sensory data alone" Why is greater accuracy and consistency, beyond sensory data alone, important in roasting, but not in extracting the coffee into an actual beverage?

You don't need a refractometer, but I don't understand if quality, accuracy & consistency are important, why they are not always important to the same degree at each stage?

Best, Mark.
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gera
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Joined: 17 Apr 2014
Posts: 5
Location: lismore
Expertise: Pro Barista

Posted Sat Apr 19, 2014, 5:20pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

boar_d_laze Said:

Gera,

My apologies for being so blunt.  Please don't take this as personal criticism; you've obviously invested a lot of time and considerable intelligence into the inquiry.

But for now, your approach seems to be to gather as much data as possible without any particular plan and either (1) hope a pattern emerges; or (2) claim a pattern will emerge but that the pattern is specific to every individual coffee.  I'm not sure which, it seems to depend on the post.  In any case, it's non-scientific, non-explanatory and insufficiently predictive to be useful as a guide to better coffee at any level of volume.  

Furthermore, you've made it clear that if there's a pattern you can't describe it; and you can't use any particular refractometer reading to guide you to making better coffee.  

Again, pardon me for being so blunt.

Posted April 19, 2014 link

Well here is what my "unplanned, non-scientific" approach thought me over the last year.
1) Extarction correlates to taste in a predictable and repeatable way. Different coffees might prefer different extraction levels depending on bean, roast, equipment and personal taste, but still - Extarction will correlate to taste in a predictable and repeatable way, unless you try it for yourself there is no other way to explain it.
2) Brew ratio is king - Nothing will affect extraction in a more aggressive and predictable way than a change of ratio.
3) Taste is non-linear. Bitter coffee DOES NOT equal over extraction. (unless you consider 17% extraction to be over extracted coffee).
4) shot time has very small yet predictable effect on extraction. Generally longer shots = more extraction, but up to a point. Depending on your equipment very long shots can show a drop of extraction, (in my case shots over 40sec).
5) grind and dose changes are almost meaningless! With a VST22 basket pulling shots to the same ratio and adjusting grind to keep shot time the same, 22g dose would taste (and extract) the same as a 21g or 23g doses. No difference regardless of the different grind setting.
6) Finer grind DOES NOT equal more extraction. a 15g dose in VST15 with fine grind might actually extract less (and taste worst, or better depending on your extraction goal) than 22g in VST22 with course grind and the same shot time, this might depend on the type of grinder, fine production, burr age, est...


boar_d_laze Said:

whether the shot is over or under extracted (bitter or sour, respectively);

Posted April 19, 2014 link

Simply not true.

boar_d_laze Said:

No device can replace your palate.  

Fixing almost every espresso problem is either a matter of adjusting temperature, grind, and/or dose; The more you know about the general principles of brewing espresso and the better you know your specific (equipment) setup, the easier and more consistent that becomes.  After awhile, it's not so much problem solving as the dialing-in process of

Posted April 19, 2014 link

That is true but I would add adjusting brew ratio as well.

boar_d_laze Said:

In my experience, there's a limit to how far you can tweak coffee.

Posted April 19, 2014 link

Well I think being able to push extraction from 10%-21% is a big tweaking range :)  

boar_d_laze Said:

no one's giving the specifics.

Posted April 19, 2014 link

This confuses me, what sort of specifics are you after? Ask and I would be happy to try and deliver :)

boar_d_laze Said:

The whole "non-linear" thing is an interesting observation, but not predictive, and consequently non-helpful.

Posted April 19, 2014 link

How can you make adjustments by taste if taste is non-linear?

boar_d_laze Said:

If I can pull a great shot dosing at 17g, I don't particularly care if I can pull a similar shot at 19.5g but not through the range of 17.5g - 19g.  Why would I?  

Posted April 19, 2014 link

Are we talking doses or extractions here? Are we using a VST basket that would not allow such big dose changes? why wouldn't you be able to pull the exact same 17g shot with 18g or 19g but only with 19.5g - doesn't make sense.
What if the 17g shot tastes great but is lost in an 8oz latte, wouldn't you like to be able to punch up the dose to 19g and be able to deliver the same great coffee even with the milk?

Hope I don't seem blunt or disrespectful, I have nothing but respect and appreciation to everyone on this site who contributes their time and energy to enhance my knowledge :)
Gera
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andys
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andys
Joined: 10 May 2003
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Posted Sun Apr 20, 2014, 8:00am
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

Hi Gera:

Thanks for your excellent contribution to this unfortunate thread. A few comments:

gera Said:

1) Extarction correlates to taste in a predictable and repeatable way. Different coffees might prefer different extraction levels depending on bean, roast, equipment and personal taste, but still - Extarction will correlate to taste in a predictable and repeatable way

Posted April 19, 2014 link

Agreed, and most coffees on conventional espresso grinders (Robur, etc) seem to taste best around EY 18.5-19.5%. The Taste Police (who insist that EY yield measurements are irrelevant) will sometimes be satisfied with shots at a lower extraction; these may taste OK, but not as good as they would be at 18.5-19.5%.

gera Said:

2) Brew ratio is king - Nothing will affect extraction in a more aggressive and predictable way than a change of ratio.

Posted April 19, 2014 link

Yes, and although degree of "blonding" is a general guide to the progress of an extraction, there is no blonding "point." Lighter-roasted coffees usually need shots to be pulled well into the blonde zone.

gera Said:

3) Taste is non-linear. Bitter coffee DOES NOT equal over extraction. (unless you consider 17% extraction to be over extracted coffee).

Posted April 19, 2014 link

And sometimes "over-extracted" coffee (ie, 20.5%+ on a Robur) tastes bitter, sometimes it just tastes dull or dilute.

gera Said:

4) shot time has very small yet predictable effect on extraction. Generally longer shots = more extraction, but up to a point. Depending on your equipment very long shots can show a drop of extraction, (in my case shots over 40sec).

Posted April 19, 2014 link

Agree with the first part, although I haven't experienced the drop you mention in the last sentence. The presumed idea behind the declining pressure profile of spring levers (and Strada-type machines) is to draw out the extraction time and thereby increase yield. But as you say, the yield increase is very small. As I mentioned on James Hoffmann's blog a while back, the most practical consequence of the declining pressure profile is to slow down the flow rate near the end and allow the barista to be a little more relaxed in terminating the shot. ;-)

gera Said:

5) grind and dose changes are almost meaningless! With a VST22 basket pulling shots to the same ratio and adjusting grind to keep shot time the same, 22g dose would taste (and extract) the same as a 21g or 23g doses. No difference regardless of the different grind setting.

Posted April 19, 2014 link

Plus or minus 1 gram in dose doesn't make a lot of difference if the brew ratio is the same. But in altering the dose by 2 or more grams I often find that Jim Schulman's assertion is correct -- the higher dose shots express the coffee's flavors more intensely.

gera Said:

6) Finer grind DOES NOT equal more extraction. a 15g dose in VST15 with fine grind might actually extract less (and taste worst, or better depending on your extraction goal) than 22g in VST22 with course grind and the same shot time, this might depend on the type of grinder, fine production, burr age, est...

Posted April 19, 2014 link

Yes, the 15g dose shots, even with finer grind, usually yield low. Perhaps the puck is getting so shallow that the brew water finds its way through without dissolving the desired amount of solids.

By the way, after extensive research I have found the earliest known photo of the Taste Police in action (attached below).

andys: taste police.jpg
(Click for larger image)

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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farmroast
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Posted Sun Apr 20, 2014, 9:15am
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

People are so hung up on ultra high scoring coffees that might work for them as brewed at a lighter roast but is then often too overwhelming as espresso. I generally select, roast and pull my own. If I get a bag of roasted I first cup it to find out it's brightness/sweetness/body, degrees of and balance of. I know if I select a pre-scored green coffee from Sweet Marias that has a ultra high brightness score even if it also has a high sweetness that the resulting espresso is going to be bright even if it can be argued as decently balanced with sweetness. To spend the extra money and then try to manipulate them with roasting and pulling is foolish imo. Kenyans are a classic example. I can appreciate most of the top scoring samples as brewed but rarely as espresso. Usually can find one not as famous/high scoring but works very nicely presenting the origin flavor desired.

 
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MarkPrince
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Posted Sun Apr 20, 2014, 2:30pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

andys Said:

Agreed, and most coffees on conventional espresso grinders (Robur, etc) seem to taste best around EY 18.5-19.5%. The Taste Police (who insist that EY yield measurements are irrelevant) will sometimes be satisfied with shots at a lower extraction; these may taste OK, but not as good as they would be at 18.5-19.5%.

Posted April 20, 2014 link

Now, you're just trolling.

Mark

 
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andys
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Posted Sun Apr 20, 2014, 7:16pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

MarkPrince Said:

Now, you're just trolling.

Posted April 20, 2014 link

Hi Mark:

It's your website, so you have the last word on who's trolling here and who's not. I will respectfully note that "trolling" was exactly the word that came to my mind when I read your first post in this thread.

I sympathize that you were subjected to the rantings of some fool(s) on Twitter who have no clue what a refractometer analysis can do and what it can't do. But IMHO, the title thread (intended sarcastically or not) is a troll: you were trying to get a discussion going by making a big deal about stuff you knew was nonsense and you knew would get the anti-measurement folks all fired up. You succeeded.

Obviously, you didn't "learn" a thing about refractometers or bright coffee; instead you simply learned something about fools who don't know what to do with refractometers.

Aside from this thread's core discussion, there are quite a few uses for refractometry in coffee making that go beyond merely dialing in extractions. Many of these uses are relevant for home coffee geeks as well as professionals. But why bother airing those discussions here, where the militantly uninformed folks hold such sway?

 
-AndyS
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gera
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Posted Mon Apr 21, 2014, 3:51am
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

andys Said:

Hi Gera:

Thanks for your excellent contribution to this unfortunate thread.

Posted April 20, 2014 link

Thank you Andy :)


andys Said:

Agree with the first part, although I haven't experienced the drop you mention in the last sentence. The presumed idea behind the declining pressure profile of spring levers (and Strada-type machines) is to draw out the extraction time and thereby increase yield. But as you say, the yield increase is very small. As I mentioned on James Hoffmann's blog a while back, the most practical consequence of the declining pressure profile is to slow down the flow rate near the end and allow the barista to be a little more relaxed in terminating the shot. ;-)

Posted April 20, 2014 link

This part I find very interesting Andy, I have seen mentions of the "extra long shot = drop in extraction" on a lecture by Ben Kaminsky as well.
I think a big part of my negative experience with long shots has also something to do with the temperature or pressure profile of the HX machine I am using. As I don't have the ability to measure them I can only estimate how this HX design might react to a 40-50sec shots.
Interestingly, Kaminsky also found no improvement to extraction using pressure profiling. However, unlike some other posts I've seen, I have found no difference in extraction when changing from a flat 58mm tamper to a flat 58.4mm tamper, but I did find them better than a convex tamper.


andys Said:

Plus or minus 1 gram in dose doesn't make a lot of difference if the brew ratio is the same. But in altering the dose by 2 or more grams I often find that Jim Schulman's assertion is correct -- the higher dose shots express the coffee's flavors more intensely.

Posted April 20, 2014 link

I have found that on most VST baskets (I think the VST22 is the only exemption), dosing more than 1g off the recommended dose, up or down, results in drop in extraction and change to flavor - haven't had a chance to explore this further yet.


andys Said:

Yes, the 15g dose shots, even with finer grind, usually yield low. Perhaps the puck is getting so shallow that the brew water finds its way through without dissolving the desired amount of solids.

Posted April 20, 2014 link

Maybe every grinder has an optimal range where average particle size and fine production create the best balance for pick extraction and either side of that range you might see a drop?

andys Said:

By the way, after extensive research I have found the earliest known photo of the Taste Police in action (attached below).

Posted April 20, 2014 link

Great picture, I made it my screen saver :P
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andys
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andys
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Posted Mon Apr 21, 2014, 8:08pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

gera Said:

This part I find very interesting Andy, I have seen mentions of the "extra long shot = drop in extraction" on a lecture by Ben Kaminsky as well.
I think a big part of my negative experience with long shots has also something to do with the temperature or pressure profile of the HX machine I am using. As I don't have the ability to measure them I can only estimate how this HX design might react to a 40-50sec shots.
Interestingly, Kaminsky also found no improvement to extraction using pressure profiling. However, unlike some other posts I've seen, I have found no difference in extraction when changing from a flat 58mm tamper to a flat 58.4mm tamper, but I did find them better than a convex tamper.

Posted April 21, 2014 link

Yes, some people speculate that 40 sec+ shots on lever machines are fine because on those machines the brew water temperature keeps dropping. This supposedly minimizes the amount of bad-tasting stuff that is extracted. On a pump machine (especially dual boier)  that brew water temp may be high throughout.

Having said that, I've made 40-50 sec shots on the Speedster with flat or slightly rising temp profiles that tasted just fine.

On the other subject, I've directly compared 58.0mm flat tampers to 58.4mm flat tampers three times. Two times showed a slight measured extraction difference, the third time no significant difference. The measured extraction differences were probably too slight to be tastable on their own, but combined with other techniques that produced slight differences could have eventually added up to a very useful result.

Whether differences in tamper dia and shape are significant depends very much on other barista technique like distribution and grooming. This makes it a bit confusing and laborious to sort it all out.

[For the refractometer skeptics] I'm repeating myself here, but IMO there are various technique and equipment options that individuallly may produce measurable yield differences that are too small to be tastable. When put together in the right combination these options may make a tastable difference. This kind of detailed work is probably too time-consuming to do by taste alone, but as you know, Gera, the instrumentation makes it possible.

 
-AndyS
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jpender
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Posted Tue Apr 22, 2014, 5:23pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

andys Said:

Agreed, and most coffees on conventional espresso grinders (Robur, etc) seem to taste best around EY 18.5-19.5%.

Posted April 20, 2014 link

Andy, is this range calculated based on the measured weight of the dose or on the dry weight of the dose? And if the latter, how do you determine what values to use for moisture and CO2?
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andys
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andys
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Posted Tue Apr 22, 2014, 5:53pm
Subject: Re: What I learned on Twitter yesterday about refractometers & bright coffee
 

jpender Said:

Andy, is this range calculated based on the measured weight of the dose or on the dry weight of the dose? And if the latter, how do you determine what values to use for moisture and CO2?

Posted April 22, 2014 link

I keep it simple and use the measured dose weight. I don't have a way to measure moisture and CO2 in the coffee anyway.

 
-AndyS
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