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Espresso Brewing Control Chart

Postby AndyS on Sun Mar 29, 2009 1:38 pm

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

Image

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. :wink:

Image

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.
-AndyS
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Postby another_jim on Sun Mar 29, 2009 1:55 pm

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.
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Postby AndyS on Sun Mar 29, 2009 2:23 pm

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! :-)
-AndyS
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Postby King Seven on Sun Mar 29, 2009 2:35 pm

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!
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Postby Sherman on Sun Mar 29, 2009 10:41 pm

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.


Well, there's a pucker born every minute...

*crickets chirping*

Thanks folks, I'll be here all week. Try the veal!

-s.
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Postby hbuchtel on Sun Mar 29, 2009 11:45 pm

LMWDP #53
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Postby charlesaf3 on Wed Apr 01, 2009 12:22 pm

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 :P )
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Postby bigabeano on Tue Apr 21, 2009 11:10 pm

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 :).
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Postby King Seven on Wed Apr 22, 2009 2:29 pm

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

So many toys and things I want!
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Postby gscace on Thu Apr 23, 2009 9:54 am

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
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