Several hours ago I posted...

HB wrote:These kinds of discussions generate a lot of heated exchanges, so I'm preemptively renewing the cooldown of this thread.

Apogee started a new thread to continue the conversation. I have merged the new thread into the original and extended the cooldown. I ask that all participants respect this call for a moment of reflection and review the Guidelines for productive online discussion, notably the admonishment "Encourage positive, shared discourse".

Apogee wrote:Wow. Them there are fightin' words! ...So I ask you HB?!...What if refractometry is simply remedial taste training for folks like myself; and you all could cut us some slack with genuine respect?

Like Peter, I simply suggest that you may be underestimating your own ability to diagnose extraction problems by taste. You prefer another method and that's perfectly legitimate. I'm not suggesting anyone's method is the only way, or even that one method is superior to another.

For what it's worth, I owned a refractometer and didn't find it helpful. But I know trainers at Counter Culture Coffee whose opinions I hold in very high regard and they think a refractometer is an invaluable tool. Maybe someday I'll have an "aha!" moment and laugh at the naivety of my earlier failures to recognize this value. And maybe not. Honestly, nowadays I'm rather indifferent to the whole subject, filing it under "different strokes for different folks".

With espresso, and other culinary endeavors I feel it it difficult to discuss because there is both a science and art to preforming and presenting the end product. With food you can present to a group a plate and typically they can relate to it and each other, they can unanimously agree if the plate tastes good or bad, this is because everyone eats. We can all recall something amazing we have eaten, as well as something absolutely terrible we would rather forget. But beyond that we can recall why it was so good; moist fish, toothsome rice, or why it sucked, burnt/overcooked/charred flavor, muddled, over salted. I believe this is because of our experiences. Most people here and in general haven't had three or more espresso a day for our entire lives, and therefor have a difficult time giving information related to why a particular espresso was amazing or why it was so terrible. We fall back on opinions and the artistic side of espresso just like the plate of food that tasted so so good. It was a delicious espresso because one could taste cherry, a thick body, and just enough acidity. This is in my option the art of espresso.

In the culinary field, one can look at a plate of food in the same way. We can really examine why we really enjoyed it. But we can only talk about why it was memorable with adjectives. We cannot say the fish tasted perfect because it was cooked to exactly 135, that is a science. Just like we cannot say we preferred the second espresso because the EY was 20%. I personally am obsessed with cooking and espresso and find them to be to incredibly similar hurdles to tackle. In my opinion cooking is just so engrained in our cultures that it is easy to view it completely as an art form. The risotto is done in this manner because it works, or the steak is medium rare when it feels this way. Espresso is no different. Again in my opinion, it is best to start with science, the exacts, and see how they correlate to the art that is cooking or extracting espresso. The two must be considered together and in fact depend on each other. We can view it through each lens, the artistic or the scientific. But in the end the only way for me to truly understand and appreciate espresso, just like food, is to understand the science and appreciate the artfulness.

HB wrote:Several hours ago I posted...
For what it's worth, I owned a refractometer and didn't find it helpful.

I took an initial pass at using the refractometer and mowed through a lot of beans, using some of the steps Apogee has outlined. My results were dreadful. To form the step in my first pass I did a fairly extensive amount of research on both this site and others about using one of these things, but did not find anything as concisely described as within this thread. Hopefully we can post a how-to article on this topic at some point on the Resources or suitable page.

I'll be doing another round of testing using some of these steps after my bean shipment arrives.

I may be a bit to much like Spock when looking at what's gone back and forth. The topic is simply about grinding up coffee beans and putting them in a machine to drink. Everyone has a point of view and a rationale. This is good. I have no idea what I'm going to learn beyond my thanks for moderating this discussion - this is even better.

Ugh. I said I was going to drop out of this thread, but now I think there's something I can say that may be useful to the readers. If not, please forgive me and I'll get lost again. Dan, I know you hate it when I do long posts, but this is a complicated subject.

I'm not going to discuss brands of refractometers, refractometer technology, how to use refractometers, accuracy, repeatibility, relative versus absolute measurements or anything of the kind. That's just going to cause more repetitive discussion. Heat but no light. Instead, I want to talk about what I believe %EY measurements are useful for, and what they're not useful for.

Extraction yield is a measure of how much of the weight of the dose has been extracted in the form of dissolved solids that wind up in the cup (I'm not going to get into the role of undissolved solids in mouth feel or taste -- that's another contentious subject.) Research done long ago produced brew charts that indicated most people prefer coffee with an extraction yield of 18%-22%. Given that research, it would be tempting to assume that if you pull a shot in that %EY range the coffee is going to taste good, or even great. But it's not that simple.

First, the research was done a long time ago, before the specialty coffee market became what it is today, and I don't believe different brew methods were tested. It's likely that taste preferences in the population have shifted since then, and that hasn't been taken into account either. In short, we really don't know what today's preference range would be and how much it varies with different coffees, roast levels, brew methods, etc. Bottom line, there's no magic %EY number or range that applies to all coffees and all brew methods.

That said, extraction yield does correlate with the acid-bitter balance of extracted coffee. I prefer to call this the sour-bitter balance because acid is often associated with brightness, which isn't what we're talking about here. It's very easy to demonstrate with almost any coffee and almost any brew method that if you don't extract enough the cup will taste sour and if you extract too much the cup will taste bitter. As it turns out, the point at which the sour and bitter flavors converge and are roughly in balance with each other is in the ballpark of the 18%-22% range found in the studies. I say in the ballpark, because it's likely the range of balance is much wider if we consider all coffees and brew methods.

I'm not sure you ever get a perfect balance where sour and bitter exactly cancel. I think coffee always has sour and bitter elements. But there's a point at which they're as balanced as they can get given the coffee, roast and brew method, and the result of that balance is that neither one dominates the taste in the cup.

Here's what I think is the most important point about extraction yield: I believe that at the point of balance, when neither sour nor bitter dominates, the subtle (or not so subtle) varietal flavors emerge. In many cases, when the cup is too sour or too bitter you can't taste these flavors. I believe coffee is usually at its absolute best when the sour and bitter elements are in balance.

That said, I wouldn't rule out that a given coffee might taste better -- to some or all people -- when it's slightly on the sour or bitter side of best balance. But it's not going to be way off from the point of balance because then the sour or bitter flavors will dominate in what most people would consider to be an unpleasant way.

So how does this make %EY useful? It has been said (even by me sometimes), that %EY can be an aid for dialing in coffee, particularly for those who have trouble distinguishing sour from bitter and those who are new to dialing in. It can even help expert tasters whose taste buds have been overwhelmed by tasting too many shots while dialing in. But that's not the whole story. You have to use %EY in conjunction with taste for the measurement to be useful. It doesn't do any good to get a number unless it correlates with what you're tasting. If you measure 19%, and the shot tastes a little too sour, you want to extract more. If it tastes bitter, you want to extract less. But what if you have trouble distinguishing sour from bitter? The %EY can help. What you have to do is compare the taste at, say 19%, with the taste at 20%. You know from the measurement that the latter is more extracted. If it tastes different, it's likely because it's more bitter (or less sour.) By practicing tasting with a refractometer, you can effectively calibrate your taste buds to detect fairly subtle differences in sourness and bitterness. Eventually, you'll have a better understanding of the effect of changing grind settings, changing the dose, changing shot time, etc.

%EY has other uses as well: QA and troubleshooting. If you dial in a shot that tastes really great, and it has an %EY of 20%, you can spot check subsequent shots to make sure they're extracted to exactly the same amount. If not, the %EY measurement will tell you on which side the error has occurred: under-extraction or over-extraction. You can make the appropriate adjustments to grind or dose or shot time to compensate and get the %EY back where it was. Or, in some cases, you may find that you can't get the %EY back to where it was because something is wrong with your equipment -- damaged or misaligned burrs, for example.

We have to be careful when talking about %EY. Lately, with the rising popularity of flow/pressure profiling machines and large flat-burr grinders, I see a lot of posts like, "I got 22% using this grinder" or "Long preinfusion gave me a 1% bump in extraction yield." Posts like this make it sound like more is always better. That's simply not the case. Try extracting the most you can out of a dark or medium roast and you'll see what I mean -- the cup will be too bitter.

We're looking for the optimum extraction yield, where the coffee tastes best, which is not necessarily the highest extraction yield. There's only a narrow set of cases where higher is often better, and that's very light-roasted coffee. These coffees can be really hard to extract, and sometimes even when the %EY looks like it would be good (say, 20%), they still taste sour. Sometimes this is due to underdevelopment, but in some cases light roasted coffees taste better at high extraction yields that would make us spit out coffee extracted from a darker roast.

I have found extraction yield measurements to be very useful, but they're not the be-all and end-all of coffee preparation. They can be very helpful for beginners, can assist when dialing in, can help to maintain quality and can be very useful for troubleshooting. They can be tools of the trade. But they cannot substitute for evaluating taste.

^that taught me a great many things in one easy to read and understand post. As someone who is fairy early in his coffee career/experience/etc, it gives me a lot of ideas as to what a refractometer is good for and what it's not.

I know it was long, but - to me at least - it was extremely valuable info. Thanks!

Peppersass wrote:We have to be careful when talking about %EY. Lately, with the rising popularity of flow/pressure profiling machines and large flat-burr grinders, I see a lot of posts like, "I got 22% using this grinder" or "Long preinfusion gave me a 1% bump in extraction yield." Posts like this make it sound like more is always better. That's simply not the case. Try extracting the most you can out of a dark or medium roast and you'll see what I mean -- the cup will be too bitter.

We're looking for the optimum extraction yield, where the coffee tastes best, which is not necessarily the highest extraction yield. There's only a narrow set of cases where higher is often better, and that's very light-roasted coffee. These coffees can be really hard to extract, and sometimes even when the %EY looks like it would be good (say, 20%), they still taste sour. Sometimes this is due to underdevelopment, but in some cases light roasted coffees taste better at high extraction yields that would make us spit out coffee extracted from a darker roast.

I have found extraction yield measurements to be very useful, but they're not the be-all and end-all of coffee preparation. They can be very helpful for beginners, can assist when dialing in, can help to maintain quality and can be very useful for troubleshooting. They can be tools of the trade. But they cannot substitute for evaluating taste.

Thank you Peppersass for writing up this useful article. As my understand, green coffee beans are RAW Food and going through roasting ( Say, Light roast is lightly processed food and Dark roast is a bit highly processed food ) So does the %EY Cannot be 100% accurate??? For me %EY Just as another good tools for improving your brewing skills.

Thank you

An interesting thought I saw on the Barista-Hustle page by Matt Perger is that it is apparently implied that when one says "got x%" it also has "and tasted good" at the end. As one who's never used a refractometer I'm not sure I interpret that from what people say, but there it is.
https://www.facebook.com/groups/barista ... 500410135/

It's only "assumed" as long as you're talking about a grinder pre-approved by that crowd. High yield screenshots of grinders like the Monoliths are suspect, for instance.

Going back to the beginning of the thread, I had asked if 10+ degrees F variation in my kitchen would affect accuracy and got (helpful) responses that it shouldn't affect the refractometer reading . But what about the nominal 0.85 brix to tds conversion? Someone posted a chart showing substantial temperature sensitivity in that relationship. I would presumably get different tds in winter vs summer, no?

Also, would this affect only the Milwaukee? The VST as I understand it does the conversion internally.

In the old days a refractometer only was reliable at the temperature it was calibrated at. If you always use standard room temp, provided that the difference in temp is not that variable , you should be OK.

http://www.brewersfriend.com/2013/04/24 ... e-brewing/

I'm using an old, but good quality device back in the day (it was used in a pharmacy), analog refractometer and do some back to back measurments for stability, using the 'illegal' brix to TDS conversion on the average (typically within 5%) after letting the sample cool down to room temp and stirring it.

Have to admit that tasting results is far easier and I hardly ever use the thing.