Brew pressure profiling update 2 - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
Alan

#11: Post by Alan »

Anyone who gets an invite to go to Greg's house for fish and coffee should immediately accept. He probably doesn't get Nick as his personal barista very often, though, so you shouldn't expect that every time.

Beyond the espresso fun, you get to drink it in a setting where you can occasionally hear horses trotting by down the hill and overlook a forest and stream that still had a bit of snow despite a week of fairly warm temperatures.

The amount of difference that tinkering with the different profiles made was pretty amazing. Since Greg spent some care ensuring that none of the profiles had high pressure water slamming up against the dry puck, it seemed like the differences between shots must be purely flow-rate related (which is coupled to the pressure which Greg was controlling off of).

Nick was dividing the shots into beginning, middle, and end. It must be known what extracts first from the coffee and what comes later. Is there agreement on what makes a shot a good one? I have to say that the first third of the shots that Nick were pulling were amazing. Extremely thick and sweet. However, they were only about a half an ounce. If those are the flavors you value, then maybe everything past about 12 seconds is just ruining the shot for you. If the goal is to optimize the taste of a 1.5oz shot, then any way of lengthening that beginning sweet spot is progress.

What about getting a rack of sample vials, dividing each shot into 10 parts and analyzing each one for density and sugar content? Then set some kind of floor beyond which those desirable characteristics are gone and make pressure/flow-rate tweaks until that floor is reached at larger and larger volumes.

To understand why the pressure differences were changing the extraction I wonder if it would be possible to fabricate a portafilter basket out of glass or plexiglas with a steel bottom so you might be able to see what the water does when it encounters the puck at different pressures.

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diab0lus

#12: Post by diab0lus »

Alan wrote: What about getting a rack of sample vials, dividing each shot into 10 parts and analyzing each one for density and sugar content? Then set some kind of floor beyond which those desirable characteristics are gone and make pressure/flow-rate tweaks until that floor is reached at larger and larger volumes.
A wine and alcohol refractometer ($58 ) could be used to analyze sugar in the espresso samples:

http://www.google.com/base/a/339982/D58 ... 8948606008

I don't know how the other components of espresso will affect the test results.

Also, this Clinitest diabetes kit ($34) will get you down to about .1% accuracy, but you might have to dilute the samples and run the test a few times in order to obtain the results you are looking for and it doesn't detect sucrose:

http://www.thewinelab.com/_fileCabinet/ ... estKit.pdf


The former Nutritional Analyst that I spoke with did not know of a portable kit for testing fat content.
-Ryan

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AndyS

#13: Post by AndyS replying to diab0lus »


No, the refractometer doesn't just measure sugar, it responds to dissolved solids, suspended fat, etc. It gives a general idea of the "strength" of the shot, but that's about it.
-AndyS
VST refractometer/filter basket beta tester, no financial interest in the company

gscace (original poster)

#14: Post by gscace (original poster) »

diab0lus wrote:I copied this post from the first thread on this topic.

Last week I tee'd the line between the pump and the boiler on my Silvia and installed a Parker series 25 NC 1/4" solenoid valve followed by a Swagelok RL3, which relieves itself into the water reservoir. This is my take on preinfusion since I am not plumbed in [it works well too]. I switch on the valve at the same time I hit the brew switch, the pressure climbs to 3 bar over a few seconds, then I power off (close) the valve once the first drop appears [no bottomless pf, yet], pressure glides to 8.2-8.5 bar and the shot continues. Anyhow, after reading what you have posted above, it makes sense to open the valve before I hit the brew switch to adjust the boiler pressure down to preinfusion pressure, then hit the brew switch. This mod could serve two purposes. Your thoughts?
It seems reasonable enough, although the RL3 is a bit pricey unless you had one lying around. You might be able to put the solenoid on a delay timer so that the low pressure part was automated. Then you could be more lazier.

-Greg

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diab0lus

#15: Post by diab0lus replying to gscace »

Believe me, I looked into adding the timer. I almost bought one, but I ultimately decided to flip the switch by eye because of my variations in technique, coffee and roast degree, grind setting and the quantity of coffee dozed.

I got the RL3 for $29.99 on E-bay. It was used for inert gas. I disassembled and boiled it when I got it, have been using it and am still alive to write about it. The precision of this valve is amazing.

I am eagerly anticipating more updates from you. I feel that this peril of pump pressure profiling is going yield results that will be beneficial to the entire coffee community, much like the pid did years ago.


This stupid software is supposed to E-mail when someone responds to my posts... :x
-Ryan