Experiments with Preground Coffee for Espresso and a Brew Pot

Coffee preparation techniques besides espresso like pourover.
Abe Carmeli
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Postby Abe Carmeli » Sat Apr 12, 2008 10:29 pm

Jim Schulman came to visit with me for a few days last week and when we were not busy gorging on some of the finest dishes New York has to offer, we managed to do a few informal experiments with pre-ground coffee. What prompted that line of investigation was Scott Rao's excellent book The Professional Barista's Handbook. In his book, Scott details the following experiment: He grounded freshly roasted coffee and let it sit for 12 hours in room temperature. He then brewed it and compared it to coffee brewed from freshly ground coffee. The 12 hours pre-ground coffee was better tasting and sweeter than the fresh ground batch. Scott speculated, that the result is also applicable to espresso brewing.

My only experience with pre-ground coffee was during the two days Jim and I spent with George Howell and Peter Lynagh at Terroir. There, a coffee that was pre-ground 2 weeks (!) ago was brewed and compared to a freshly ground brewed coffee. The purpose of that experiment was to compare properly stored green coffee (vac packed at origin) with badly stored green coffee (jute bag). The properly stored coffee pre-ground 2 weeks before brew beat the badly stored green freshly ground by a mile. However, that two week old batch was no match for a freshly ground sample of the same coffee.

First Experiment: Brewed Coffee

So, with that in mind, we designed two experiments: In the first one we essentially repeating Scott's experiment. We pre-ground a batch of 2 day old Geisha Esmeralda (Jim's roast) and waited 12 hours. We then brewed it in the Eva Solo (soak Pot) for four minutes at 198 f 8 oz water and 13.6 grams ground coffee. At the same time, we freshly ground the same coffee and brewed it side by side in another pot.

I invited my friend Lisa to join us in the blind tasting. In this experiment, Jim & I played the role of the somewhat refined coffee connoisseur, while Lisa played the role of the average Lisa.

The result was unanimous: The pre-ground coffee was sweeter, and as a whole better integrated. It still had all the high notes that I thought may get lost somewhat in 12 hours, and it was somewhat rounder.

Second Experiment: Espresso

In this experiment we used two different coffees. The first was a typical espresso blend we picked up from a coffee shop in the city. Barrington Espresso Blend, from Joe The Art of Coffee. That coffee was not more than 5 days from roast. The second was a single origin Jim roasted Worka - a relationship coffee from Sidamo sourced by Ric Rhinehardt and it was three days from roast. We pre-ground a shot 30 minutes before brewing it and compared it to a freshly ground shot of the same coffee. We chose 30 minutes due to the Italian conventional wisdom about storage of ground coffee in the doser. (The Italians pre-grind coffee to fill-up the doser and then dispense it per shot.)
Here we got split results:

The Barrington blend (15.5 grams 1.7 oz 198f 27 seconds): The 30 minutes pre-ground came on top. The shot was better integrated, rounder and a bit sweeter. There was no loss in flavor profile.

The single origin shot (14.5 grams 198f 1.5oz 26 seconds) was the reverse. The freshly ground came on top, it was richer and more complex; one of those shots I would give a 5 in a barista competition.

There was one area where the pre-ground shot was ugly on both experiments: The extraction, as viewed on a bottomless p/f. The pre-ground was uneven to the extreme, and yet, despite it, it tasted better with the Barrington blend.

Those results require more experimenting, with larger samples to get a clearer view of what's going on there. Scott believes that pre-grinding creates a more even distribution of CO2 in the coffee bed and thus more even extraction which results in a more balanced and sweeter cup.

The brewed coffee experiment has been repeated by others, and I hear they all came to the same result: pre-ground was better. The espresso on the other hand is very intriguing, and I think it is coffee dependent. This is only an uneducated guess. Time from grinding plays a bigger role in espresso, and I doubt a 12 hours pre-ground espresso will be a match for a freshly ground batch.

A tentative conclusion here would be that sharper coffees (overly acidic for example) will benefit from pre-grinding for espresso.

It is also important to note, that there was no difference in crema or the way the shot looked in the cup between the ground and pre-ground.
Abe Carmeli

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Postby RapidCoffee » Sat Apr 12, 2008 10:46 pm

That was the one big surprise for me in Scott's book. To say this rocks one foundation of my coffee universe is an understatement. I'd always taken grinding immediately before brewing as a given. Now I have to chew on the implications of pregrinding, and it's causing a certain amount of indigestion...

Regardless, thanks for replicating Scott's findings. Nice work!
John

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Postby hbuchtel » Sun Apr 13, 2008 2:50 am

Wow... thanks for the post!
Abe Carmeli wrote:The Barrington blend (15.5 grams 1.7 oz 198f 27 seconds): The 30 minutes pre-ground came on top. The shot was better integrated, rounder and a bit sweeter. There was no loss in flavor profile.

The single origin shot (14.5 grams 198f 1.5oz 26 seconds) was the reverse. The freshly ground came on top, it was richer and more complex; one of those shots I would give a 5 in a barista competition.

I'm a little confused here, were you saying that the pre-ground flowed at the exact same rate as the freshly-ground? (ie Xoz and Xseconds were the same for pre and fresh)

Another question, do any of you have an opinion about how many days (or what range of days) post-roast the blend and SO are best at?

Thanks, Henry
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Postby Jacob » Sun Apr 13, 2008 3:26 am

RapidCoffee wrote:Now I have to chew on the implications of pregrinding, and ...

Using the doser as a - well as a doser :shock: :lol:
Grinding the for the next session at the end of the previous and have a kitchen that always smells of fresh ground coffee :D

Am I still asleep, dreaming?

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Postby Compass Coffee » Sun Apr 13, 2008 4:09 am

Particularly with the 2 day post roast Gesha I wonder if the results of the 12hr ground being the better cup versus fresh ground was a result of relatively short rest. Be interesting to repeat at 6 or 7 days post roast, more where I find Esmerlda to be at it's balance peak.
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Postby RapidCoffee » Sun Apr 13, 2008 6:57 am

Compass Coffee wrote:Particularly with the 2 day post roast Gesha I wonder if the results of the 12hr ground being the better cup versus fresh ground was a result of relatively short rest. Be interesting to repeat at 6 or 7 days post roast, more where I find Esmerlda to be at it's balance peak.

I'm sure this is a big part of the puzzle. I don't have Scott's book in front of me, but I believe he suggested CO2 degassing as the reason why pregrinding would be beneficial.

Espresso uses a finer grind than drip, and will probably not tolerate long pregrinding delays. I've seen huge changes, visually and taste-wise, in shots pulled with coffee that was ground a day before.
John

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Postby Abe Carmeli » Sun Apr 13, 2008 9:58 am

hbuchtel wrote:Wow... thanks for the post!

I'm a little confused here, were you saying that the pre-ground flowed at the exact same rate as the freshly-ground? (ie Xoz and Xseconds were the same for pre and fresh)
.

On the Barrington it was the same, on the single origin it was slightly faster with the preground. (2 seconds)

Another question, do any of you have an opinion about how many days (or what range of days) post-roast the blend and SO are best at?


The Barrington is best on day 4-5. The single origin was best at day 3-4 in my opinion.
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Postby another_jim » Sun Apr 13, 2008 10:45 am

hbuchtel wrote:I'm a little confused here, were you saying that the pre-ground flowed at the exact same rate as the freshly-ground? (ie Xoz and Xseconds were the same for pre and fresh)


We initially tried grinding a bit finer for the half hour wait shots, but it turned out to be unnecessary.

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Postby hbuchtel » Sun Apr 13, 2008 7:17 pm

Abe Carmeli wrote:On the Barrington it was the same, on the single origin it was slightly faster with the preground. (2 seconds)
another_jim wrote:We initially tried grinding a bit finer for the half hour wait shots, but it turned out to be unnecessary.

Yet another surprise...

Anybody know what beans are in the Barrington blend?

from barringtoncoffee.com wrote:We carefully roast and blend this coffee to bring out the finest qualities of espresso coffee--sweet caramel, chocolate, spice and hints of dried fruit. When properly extracted it yields spectacular crema and a long smooth finish. To attain this perfection, we source coffees that are naturally very low in acidity and extraordinarily high in body. When the otherwise subtle and delicate flavors of these coffees are concentrated through the high pressure extraction of an espresso machine the qualities are magnified to an essential level. Our proprietary blend includes aged and conditioned coffees from Asia and South America.


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Postby cannonfodder » Mon Apr 14, 2008 12:58 am

Very interesting. This may be another dogma that is destine to fall. Just like freezing coffee, I blindly followed the masses assuming what was preached about freezing beans being bad as gospel. That dogma is now defunct and I now freeze beans to preserve freshness. Now preground coffee is better than fresh ground. What's next, dogs and cats living in harmony, peace in the middle east? Where will it all end. I will have to grind a couple shots worth of coffee tomorrow morning before I shower and try out some preground espresso.
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