Fine grind / small dose versus coarse grind / big dose: Is there a difference? - Page 2

[cpl593h]

I just pulled some transcendent shots of Oromia Yirg roasted to City+. I never intended for this to be espresso, but dosed way down to 16g and pulled normale, it's everything it is in the cupping spoon - floral, light, citrusy, tea-like, but not out-of-whack. It's a dense coffee, so 16g doesn't sound like a small dose, but it was scoop leveled with my index finger, and after tamping, only occupied half the volume of the basket.

[Jasonian]

Sounds quite a bit like Terroir's Yirgacheffe addis ketema SOE.

Is the growth of the wave of this discovery going to move the US into the direction of what our friends in Scandanavia are doing?

I hope so.

(super light roasted El Salvador SHG Guadelupe awaiting use as a SOE)

[another_jim (original poster)]

Sounds quite a bit like Terroir's Yirgacheffe addis ketema SOE.

Is the growth of the wave of this discovery going to move the US into the direction of what our friends in Scandanavia are doing?

I hope so.

I just hope it makes varying the dose a standard part of the barista skills palette. Hindsight is always 20/20; but in retrospect, with all the endless discussions of temperature, pressure, tamping, machines, etc., it sure seems very odd that dosing has never been put under the microscope.

[Dogshot]

Huh, just this afternoon I was thinking about starting a thread about making sense of dosing. It is usually the last variable that I play with, mostly because I have no heuristics or theory or anything other than trial-and-error to guide my trials (and errors).

However, this thread and Cannonfodder's thread about dialing in the Elektra A3 has made realize a few things:

1) the machine and basket have an ideal volume of coffee for easy brewing, and

2) the amount of coffee used and the final volume in the cup vary systematically with taste.

So, when someone suggests 17.5gms in a double basket at x temp and y volume, or 19gms in a triple basket at x temp and y volume, the usefulness of the description is somewhat limited by the machine and basket in use.

This thread has really expanded my horizons on brewing, and has led to big growth in my brewing skills. Today I received a lb of PNG Mawari in the mail from a local roaster, and blanched when I saw how lightly it had been roasted. Instead of my usual routine of going with the dose that extracts best on my machine and starting work on temperature and pour volume, I tightened the grinder, down-dosed by doing just a WDT sweep, and brewed at a medium-high temp. The pour was long at around 2oz, maybe 2.25oz (which is long according to my former standards). It was a really good shot.

Now I start to dial in with dose and volume. I dose lighter and longer for light or bright roasts and heavier and shorter for dark or strong roasts. Don't northern Italian cafe's tend to pour longer shots and southern Italians pour tight shots? My early impression is that this may also substitute to some degree for temperature adjustments (which might explain for me why Jim's impression that temp mgt is not that crucial differs so greatly from my experience to this point).

I'm rambling - the only point I wish to make is that making sense of dosing would be a great topic, and gets my top vote for an in-depth article by one of our resident experts to start to tackle. I'm sure it would lead to some revelations.

Mark

[Jasonian]

Delving into it too far will result in research farther into the realm of roasting than even a lot of commercial roasters have done.

How does the extraction chemistry change with different roast levels, roast rates, roast temperatures, heat types, and so on.

And beyond that, what about soil content, ambient humidity, altitude, and beyond that, different species under these different conditions.

And processing. Let's talk about green coffee processing. How does this vital link in the chain effect the chemistry during roasting, and thus, the chemistry during extraction?

Now let's talk about extraction again. Which of these 500+flavor components are desirable, and at what extraction parameter does it dissolve?

More simple than that, how does the extraction differ in different volumes of water in constant contact under the same pressure, and the same temperature? We can't even really hit that kind of precision on our equipment, but let's pretend we can. How does the extraction differ between 14 grams in a double basket, and 14 grams in a triple basket? What kind of an effect does the spacial volume of the water cushion have on the extraction?



Jason "still waiting for the glass portafilter assembly" H.

[another_jim (original poster)]

Delving into it too far will result in research farther into the realm of roasting than even a lot of commercial roasters have done.

How does the extraction chemistry change with different roast levels, roast rates, roast temperatures, heat types, and so on.

And beyond that, what about soil content, ambient humidity, altitude, and beyond that, different species under these different conditions.

And processing. Let's talk about green coffee processing. How does this vital link in the chain effect the chemistry during roasting, and thus, the chemistry during extraction?

Now let's talk about extraction again. Which of these 500+flavor components are desirable, and at what extraction parameter does it dissolve?

More simple than that, how does the extraction differ in different volumes of water in constant contact under the same pressure, and the same temperature? We can't even really hit that kind of precision on our equipment, but let's pretend we can. How does the extraction differ between 14 grams in a double basket, and 14 grams in a triple basket? What kind of an effect does the spacial volume of the water cushion have on the extraction?

I dislike complexity; so I have a very simple model for most of these things that I'll be publishing within the next two weeks. Stay tuned; here's the trailer:
-- the amount of puck extracted is proportional to puck dry weight divided by basket hole area. If the shot is stopped by color, then shot time and volume play only a very minor role.
-- fruit acids extract first and fast, caramels and bitters at nearly the same, much slower rate, bitters maybe a shade slower than caramels. The clockwise order on Lingle's flavor wheel is about right for predicting what will be in the cup from low to high extraction levels; however, the lower and more trigger-like taste thresholds for bitters distorts this slightly when tasting the shots.

[Jasonian]

Interesting.

I'm looking forward to the full report.

[another_jim (original poster)]

I've put up a page with a write-up of my research. I apologize for it being in science-journalese; I'll translate it into English in subsequent drafts. For those willing to wrestle through it; I'd appreciate comments.

[jesawdy]

From the paper:

At these low extraction levels, high grade coffees become a bane rather than a boon, producing jarringly acidic shots. So, in the specialty coffee world, there is a feverish search on for ultra-sugary high grown coffees that are still sweet when roasted light and underextracted. When such coffees are not available, one gets the ubiquitous medium-dark roasted blends that are a far cry from the quality of the specialty coffees sold for regular brewing.

And all this because of an unintended consequence of using fresh coffee. I think it's high time for baristas to relearn their dosing.

A final note. Since posting early drafts of this paper, I have found out that this is changing. In Scandinavia and Australia, many top competing baristas are replacing their fingers with curved swipers that scoop out ground coffee below the rim level of the basket. By having a french-curve like set of these, they can efficiently vary the dose in a workplace or competition context. I'm sure these "3rd wave" dosing tools will become much more prevalent and developed as the word gets out.

So I assume that you are a big fan of fine grind, low dose right now? Do you have any excessive trouble in channeling, and soupiness of the puck? When I dose low (on Silvia at least), it will look pretty good on a bottomless extraction, but the puck will be soupy and some evidence of pockets and/or pin holes. Or are you only pulling singles and find low doses to be simpler?

US Barista champ(Correction) Australian Barista champ, Paul Bassett has also developed said leveling device, I read it about it some where and can't remember where. Can you point me to any information on the other leveling devices you have come across?

[Dogshot]

Very interesting study Jim, and congratulations on producing something that I'm sure will be referred to in future as often as your water FAQ. I look forward to getting the chance to send you a few comments, if you don't mind.

One interesting thing: to maintain the same extraction ratios, assuming that the PF size represents the diameter of the surface area of the bottom of the basket (a rough guide for double/triple baskets), here is what one should be dosing:

58mm PF - assume 15gm dose.

53mm PF - same extraction requires 12gm dose (perhaps this is why La Spaz has such a thick dispersion screen, with the option to get an even thicker one).

45mm PF - same extraction requires 8.7gm dose. I am very interested to hear if any Ponte Vecchio owners are dosing down as low as 10gm in their double basket.

...or have I misunderstood the concept of P/A ratio and extraction?

Jeff - Although I am a devout Eurocurve tamp user, my limited experience shows that when I dose below 16gm, the flat tamper gives better results (less pinholing).

Mark