Many of you are familiar with the "Coffee Brewing Control Chart," an example of which is posted below (thank you, SCAA):



What's the significance of the chart? Well, to brew the best coffee, most experienced tasters agree that you want to extract about 18-20% of the dry matter in your original ground coffee, AND you want to dilute it down to about 1.2 - 1.4% in the resulting cup of coffee.

Accomplishing both these tasks simultaneously is not trivial. Simply using a specified water to coffee ratio (eg, 16:1 by weight) is not enough. You also have to adjust the grind, brew water temperature and steeping time to hit your personal sweet spot (ie, EXTRACTION - solubles yield) for each coffee. It's sort of like hitting a dartboard from three or four times the regulation distance: without considerable practice, the target begins to get quite small, indeed.

My experience is that the extra effort is worth it. My brewed coffee definitely improved when I started experimenting with this.

But mostly I drink espresso. So posted below is the Espresso Brewing Control Chart.



This espresso chart differs from the coffee chart in several ways:

(1) The TDS scale (y axis) is in a much higher range, since espresso is so much more concentrated than brewed coffee.

(2) The Yield scale (x axis) reflects Solids Yield, rather than Solubles Yield, since espresso contains significant amounts of undissolved particles and emulsified oils.

(3) The brewing ratio calculation is different for espresso. For espresso, it's easy and practical to define the brewing ratio as coffee dose weight / beverage weight. For coffee, it's more practical to define the brewing ratio as coffee dose weight / brew water weight. This is because with coffee, one can conveniently measure the amount of water one adds to the grounds. In espresso, one normally can't measure the brew water directly, but it's easy to measure the weight of the resulting beverage.

Because these two calculations are similar yet different, it's useful to keep them from getting confused by referring specifically to Coffee Brewing Ratio or Espresso Brewing Ratio.

So, I hear you all saying (the roar is deafening), it's a nice chart, but why should I care?

Honestly, I'm not sure you should care, yet. But testing indicates that this approach may help us to control and understand how we get certain flavors in our espresso. For instance, rather predictably, espresso extracted on the low side of solids yield (say 15-16%) tastes sour for many light-roasted coffees and "green" for many darker-roasted coffees. Espresso extracted on the high side (say 20-23%) begins to taste harsh or bitter. Note that these observations are more or less independent of the espresso concentration (ie, ristretto or lungo), they refer to the percentage of solids that are extracted from the original dose.

How does one measure solids yield? In the first part of his landmark paper, Jim Schulman talked about oven drying used espresso pucks to determine how much of the original material had been removed. It's a tedious process, but gradually easier and faster methods are being developed, and they will soon be applicable to espresso. "Soon" means hopefully at the Atlanta SCAA show!

I know there are a lot of experienced coffee people who are skeptical of this sort of numerical approach to coffee and espresso. "Screw the numbers," they snort. "I go by my taste buds."

Obviously, the numbers can't possibly replace taste buds. They can only augment them, aid in quality control, and help in the diagnosis of problems. But I do know this: I have had many mediocre coffees at shops run by these snorting, experienced skeptics. And once their "golden taste buds" walk out of the shop, employees with less developed taste buds are left in charge. The results aren't always so golden. With the proper use of objective measurements, quality control at these shops could be greatly enhanced.

Notes:
a. Yes, the TDS numbers listed on the SCAA chart are off by a factor of 10. For instance, 1.3% is actually 13,000 parts per million, not 1,300.
b. Brewing ratios can be displayed in different ways. I use the SCAA method, with the coffee dose in the numerator, and the result expressed as a percentage (eg, 6%). Terroir Coffee, for instance, does the inverse when they calculate their "Brew Formula": coffee dose is in the denominator, and the result is expressed as a ratio (eg, 16.7:1).
c. If one knows any two out of the following three variables, one can always calculate the third: Espresso Brewing Ratio, Solids Yield, TDS.
d. The Espresso-style brewing ratio can also be used for brewed coffee, where it does have some advantages. But it isn't commonly done.

So brix metering is ready for prime time?

Is this about right?:

-- The brix (refractometer) reading is proportional to the non-water content (NWC) in the espresso.
-- The software or a conversion chart can determine the actual proportion of NWC from the brix reading.
-- Weighing the shot will get you from the proportion of NWC to the weight of NWC
-- Dividing the NWC weight by the initial puck weight gets the solids yield.

Iirc, you came up with the puck baking technique, then suckered me into doing it. I sure hope this is less smelly.

another_jim wrote:So brix metering is ready for prime time?

It appears to be getting close.

another_jim wrote:Is this about right?:

-- The brix (refractometer) reading is proportional to the non-water content (NWC) in the espresso.
-- The software or a conversion chart can determine the actual proportion of NWC from the brix reading.
-- Weighing the shot will get you from the proportion of NWC to the weight of NWC
-- Dividing the NWC weight by the initial puck weight gets the solids yield.

I believe so. The "about" part concerns how reproducible the first two items can be when using various coffees, roast levels, and extraction parameters.

another_jim wrote:Iirc, you came up with the puck baking technique, then suckered me into doing it. I sure hope this is less smelly.

That's why some bright person invented oven exhaust hoods!

This is awesome, thank you so much!

I am a huge fan of using control charts in conjunction with my tastebuds (science and art can be friends...)

This is brilliant, and something I've been thinking a lot about and should be very helpful for increasing genuine and useful communication about how to brew a coffee, and how that brewing recipe will affect its taste.

Another step closer to killing the use of volume of shots when talking about espresso! Huzzah!

Pun for the Ages- NYTimes

Really impressive work.

(ironically people who know me think I'm obsessed about coffee. I want to carry a copy of this thread to show them I'm still just starting to take it seriously )

I'm curious if anyone here visited the George Howell Coffee Company booth where they were displaying their new "GotMojo" (the next generation of their phenomenal ExtractMojo) software?

Vince Fedele, the inventor of the system has now adapted it for measuring espresso extraction and brew strength, working with Andy's ideas about "espresso brewing ratio".

For those crazies among us who have oven-dried espresso pucks (god help you if you have others living in your house when you do that) and took pains to measure how much mass was extracted from pucks of grounds, this whole system seems like something of a miracle, second only perhaps to an iphone.

It's very difficult to convince someone how much control you have over espresso (or drip coffee) flavor using Vince's system, which is basically a high tech, interactive version of the chart Andy posted here, used in conjunction with a calibrated, precise refractometer that measures brew strength.

Andy, as usual is right on. We've all walked into well-regarded shops that are supposed to make such stellar coffee but then received forgettable, or worse, espresso. Usually these cafes are quite inconsistent and they pretty much never use any objective tools to measure their extractions. If you work at a shop and believe it's perfectly consistent, then I challenge you to actually start measuring your extractions. Some of what the system shows is humbling.

If I owned a shop and was considering upgrading my grinder or espresso machine, I'd be far better off spending a few hundred dollars on this system to measure extraction and brew strength than several thousand dollars on a nicer machine, only to produce the same inconsistent and often subpar extractions.

For what it's worth, I'm certain I've NEVER been to a shop that pulls more than 80% (I'm being kind) of its shots in the 19-20% extraction range.

TRUST IN SCHECTER. Try measuring your extractions. It's fun .

I didn't know it could be adapted for espresso. Now I am really, really tempted.

So many toys and things I want!

another_jim wrote:So brix metering is ready for prime time?

Is this about right?:

-- The brix (refractometer) reading is proportional to the non-water content (NWC) in the espresso.
-- The software or a conversion chart can determine the actual proportion of NWC from the brix reading.
-- Weighing the shot will get you from the proportion of NWC to the weight of NWC
-- Dividing the NWC weight by the initial puck weight gets the solids yield.

Iirc, you came up with the puck baking technique, then suckered me into doing it. I sure hope this is less smelly.

I asked Barry (Jarrett) about this system at the show because I was sorely tempted to part with the money. Barry said that the refractometer didn't measure non-soluble components and that non-soluble components account for a large part of the espresso experience. Since they are obtained from the grinds, the correlation to extraction ratio isn't all that good for espresso, although it was quite good for brewed coffee. Was I missing something?

What I took away from Barry's comment is that baking pucks is still the best way.

-Greg

Would be interesting to see the difference between refractometer and baked puck data, to see if there is some sort of correlation between the two, to allow you to factor in accurately what you might not be able to see with the refractometer?

What I should have done while I was there was to pose that question directly to George Howell and his minions to see if they had the data and if they had thought it through. I suspect one still could do so by phone.

-Greg

Iirc, Andy did some experimenting along this line several years ago and got a strong correlation between the refractometer readings and the baked puck data. So the refractometer readings, properly scaled, can be used as a measurment of extraction. However, there wasn't enough of a data set to determine whether the correlation was unaltered when using different coffees, baskets, grinders, etc. Worst case, the refractometer readings need to be scaled differently under different conditions.

I'm not sure how much data Vince collected, and whether a peer review would pass on his scaling algorithm. When I first heard about it, I was personally loath to take on the job of collecting a dataset large enough to create a sound conversion table (for instance, I doubt the SCAA did enough in the 50s for their conversion from conductance to yield to be sound, their raw data never saw the light of day, nor did it make it into a peer reviewed article)

On the other hand, in a shop environment, a conversion table is not necessary. Suppose the refractometer (or conductance) reading is monotonic with the solid + solubles concentration in the cup. That is, reading = function(solids + solubles) and the function is invertible. Let the inverse be S(*) the unknown scaling function that converts the reading back to the concentration. This scale is monotonic, and can be treated like the actual measurement in arbitrary and unknown physical units. Like units of old, they can be different from coffee to coffee and shop to shop, but within a tight context, they work.

Basically, one can, for every setup (grinder, blend, baskets), take refractometer readings and divide them by shot weight to get this arbitrary but accurate extraction measure. One can therefore reliably use it to learn how that measure changes when changing dose, shot time, etc., and which extraction level tastes best. One can then spot check that the same extraction value is being maintained in operation. This is no different than what one would do if the scale was correct.

So I think Vince's system can work whether the scale is correct and transferable or not, as long as it is consistent in any one setting. On the other hand, the same can be said for a $30 brix meter on its own. The software also has convenience and administrative tools; and for a cafe that may make it very worthwhile. I'm less sure if these extras' are valuable in a home setting.

Personally, since there are many brix meters available with a wide range of costs and features, I would prefer if we used raw brix and brix*shot_weight/dose_weight readings to communicate concentration and the extraction measures. That way we can compare notes, and discuss possible conversion algorithms in the open context of scientific discussion. If we use the Terroir system while it is unpublished, we are using something that seems very odd to me, a physical unit which is proprietary and trade secreted.

While reading up on refractometers I got slightly confused about Brix. Wikipedia states: Degrees Brix is a measurement of sucrose in a liquid. Is the Brix mentioning in this topic therefore misplaced? Or does it correlate to brewing ratio somehow?

CHeers,

Bas

On "brix meter" refractometers, the most common kind, the refraction angle from the refractometer is converted into a brix reading, which is the amount of dissolved sugar in the liquid. The amount of dissolved sugar will be directly proportional to the amount of total solids that get into the cup for a given coffee and brewing method. Whether it is the same proportion for all coffees and brewing methods remains to be seen. Since the amount of sugars in coffee varies by varietal, region and degree of roast, I doubt it.

gscace wrote:I asked Barry (Jarrett) about this system at the show....

Greg: Of course a refractometer measures only dissolved solids. That does not mean it cannot be used to derive excellent results in measuring espresso solids yield.

Sorry guys, I don't have time for a long post now. But this weekend I will try and furnish some actual data to try and balance the mix of misinformation and wild speculation that has suddenly appeared in this thread.

I confess to being pretty ignorant, for sure.

-Greg

gscace wrote:I asked Barry (Jarrett) about this system at the show because I was sorely tempted to part with the money. Barry said that the refractometer didn't measure non-soluble components and that non-soluble components account for a large part of the espresso experience.

Has Barry actually compared results obtained from dehydration to those obtained using accurately calibrated refractometers? I doubt it.

Perhaps non-soluble components account for a large part of the "espresso experience", but that doesn't mean they're a large part of the extracted mass; Illy says that masswise the insolubles comprise about 10% of the total. This is a small enough part of the whole that the method will be pretty accurate even if the solubility varies.

[Say you had two coffee that were very different, so that the insoluble fraction was 8% for one and 12% for the other. And say the refractometer scale, which uses only the soluble portion, returned a 20% total solids yield for each one. They would still be within 1% of each other if the total extracted solids were measured by dehydration. That's good enough to hit the sweet spot.]

Greg, the use of refractometers for brewed coffee has tons of science behind it, and Terroir has extensively tested their instrument and software to measure it. The brewed coffee refractometer is the one that was for sale at the show.

The use of refractometers for espresso is still in the early stages. There are only a handful of the Terroir-calibrated espresso instruments in existence. They won't be ready for distribution until June at the earliest. But so far they seem to be operating well. I recently did several rounds of tests comparing dehydration to the espresso refractometer and Vince at Terroir did a bunch in Boston. The refractometer technique takes care, and therefore it's not infallible, but believe me, dehydration testing is not infallible either.

Below is a graph showing total solids yield derived three ways: drying the puck, drying the espresso, and using an earlier version of the Terroir Espresso Refractometer. There are some weird outliers, but in general the agreement is very good. Below that is a chart showing the actual data. ["nD" stands for refractive index, IOW, the refractometer reading]

another_jim wrote:On "brix meter" refractometers, the most common kind, the refraction angle from the refractometer is converted into a brix reading, which is the amount of dissolved sugar in the liquid. The amount of dissolved sugar will be directly proportional to the amount of total solids that get into the cup for a given coffee and brewing method. Whether it is the same proportion for all coffees and brewing methods remains to be seen. Since the amount of sugars in coffee varies by varietal, region and degree of roast, I doubt it.

Wrong, wrong, wrong, wrongity wrong.

"Brix Refractometers" read the change in density resulting from ALL the dissolved components in solution, not just sugar. They are calibrated to read % sugar, but this calibration is accurate only for sugar solutions, and obviously, the solubles in coffee are NOT pure sugar.

In addition, since refractive index varies with temperature, Brix Refractometers are often "temperature compensated" to give accurate results over a reasonable range of temperatures for sugar solutions. Since the curve of refractive index for sugar solutions vs temperature is different from the corresponding curve for coffee solutions vs temperature, errors can be introduced when brix instruments are used for coffee. A "Coffee Refractometer" or an "Espresso Refractometer" is programmed with temperature compensation curves different from those appropriate for sugar.

another_jim wrote:Personally, since there are many brix meters available with a wide range of costs and features, I would prefer if we used raw brix and brix*shot_weight/dose_weight readings to communicate concentration and the extraction measures. That way we can compare notes, and discuss possible conversion algorithms in the open context of scientific discussion. If we use the Terroir system while it is unpublished, we are using something that seems very odd to me, a physical unit which is proprietary and trade secreted.

The "Terroir physical unit" is not proprietary or "trade secreted." On the contrary, the coffee instrument reads TDS (total dissolved solids). The espresso instrument (under development) reads TBS (total brew solids, ie, dissolved + undissolved solids).

These are NOT proprietary measurement units, they are exactly the everyday units that we need to do this work.

If you are skeptical that the Terroir refractometers work as advertised, you could buy or borrow one and run your own dehydration comparison. But to ignore the logical measurement units that have been around for 60 years, and propose a new standard measurement using brix, is a huge and totally unnecessary step backwards (IMHO).

P.S. The technology that makes the Terroir instruments work IS proprietary, but I guess once the patents are published (late this year?), you'll be able to read all about it.

Andy, you're absolutely right on the refractometer and the units, but I'm not ready to concede my main two points, which are:

-- The consistency of correlation of refractometer readings to solids concentration and extraction is not known. Your data are a start, but it'll take data from a variety of settings to get some certainty. Pure noise is less of a problem, since that can be dealt with by doing multiple readings (good practice in any case, since there's always operator error, and a huge plus for a simple, non-destructive method like the refractometer over puck baking). I'm more concerned with systemtic errors due to different conversion constants for different coffees, grinders, baskets, etc.

-- The conversion that Terroir uses is unpublished. Until it is, it would be better to communicate with the most widely available units, e.g. brix for refractometers and CaCO3 concentration for conductivity meters.

These points are temporary. More testing will reveal the method's limit conditions, and a patent application will state the conversion algorithm.

BTW, while algorithms are patentable, a patented conversion algorithm may not be much protection. Anyone who has college algebra can do a Taylor expansion of the algorithm for the numerical range of interest, then use any equation that has the same expansion for that region as the "new improved" conversion algorithm.