Posted Sun Sep 5, 2004, 11:55pm Subject: How to Minimize Sour Taste at Beginning of the Pull?
I have been noticing some sour notes in my espresso of late. I swapped cups half way through a pull today and the cup containing the first half of the pull was extremely sour, whereas the second half was perfect. Are there any rules of thumb on what causes an excessive sour taste early on? I know you can let the first few ml go into the drip tray, but I think that is kind of a waste.
Posted Mon Sep 6, 2004, 7:09am Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
Too fast an onset can produce a sour taste, but since you didn't mention that, I'll assume the extraction is correct... so I would look to the pull temperature.
I've been studying HX performance lately to better understand the dynamics of the cooling flush amount, pressurestat setting, and design differences (e.g., length of the HX, how much is immersed in water, path length / diameter of the thermosyphon, etc.). Independent of the HX machine, they all exhibit what I call the "HX hump" at the beginning of the shot, shown in the diagram below.
I've noticed two things the operator controls that affect the HX hump, especially on prosumer E61-type machines -- how much is flushed, and how long an interval between flushing out the HX and pulling the shot. The flush amount tends to affect the mid-to-tail end of the curve. The "pause before the pull" tends to affect the very early part of the shot, either producing a prominent hump, a flat one, or if there's little or no delay, it disappears completely and the curve becomes more of like a straight rising line (or *horrors* the inverted U).
It's just a guess, since not all machines act like this (for example, very little of the above applies to the Cimbali Junior, whose design is very different from the E61). But if temperature is at fault, I would guess that the early part of the curve is too flat, and that's usually because (a) the flush amount was a tad too much, or more likely (b) the pause before pulling the shot was not long enough for the HX to recover.
I'm still working on it, but so far, the ideal pause time for most of the E61s I've measured is somewhere around 30-45 seconds. It is certainly less than one minute, although I've yet to do systematic measurements. I don't know your particular machine -- a quick test would be to slow your pace by about 25%. That will spike up the HX hump and should eliminate any question of low initial temperature being at fault.
Posted Mon Sep 6, 2004, 9:14am Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
Hi Dan,
Thanks for the explanation. So just to make sure I understand this completely, you are saying I should: 1) flush water from the HX (assuming it has been sitting idle for a while and has overheated the HX water) 2) wait 30 to 45 secs 3) pull shot
Posted Mon Sep 6, 2004, 10:49am Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
Yes, you understood correctly, i.e., my guess is that you're short-changing step 2. Depending on the machine, skipping it either (a) doesn't matter, (b) produces a flatter rising line, or (c) produces the dreaded inverted U. Below is this morning's shot and an example of one of the best HX temperature profiles I've measured (top of puck). The goal for this blend was to produce a curve that "straddles" the target temperature of 201F, with the HX hump going over and the natural drop finishing just below.
Oh yeah, all this blathering about temperatures aside, it was a very good tasting shot. :-)
Keep in mind that to a large degree, this is really temperature accuracy "for sport." Getting within a degree or two is more than accurate enough for my taste abilities, which isn't difficult to do consistently just by observing the "water dance" during the cooling flush. Finally, the extraction itself is equally important and doesn't require fancy equipment to perfect.
Which reminds me... I am eyeballing the bottomless portafilter. The good folks at Counter Culture Coffee had one at last Friday's espresso lab and it sure makes for pretty shots. Not yet convinced it improves the taste, however. There's little doubt that it enhances your ability to diagnose channeling. That's another possibility which could explain the initial sour taste -- a puck with small fissures that initially contribute to overextraction, but then seal when it expands in time to save the last two-thirds of the shot.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Mon Sep 6, 2004, 1:02pm Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
strugs Said:
I have been noticing some sour notes in my espresso of late. I swapped cups half way through a pull today and the cup containing the first half of the pull was extremely sour, whereas the second half was perfect. Are there any rules of thumb on what causes an excessive sour taste early on? I know you can let the first few ml go into the drip tray, but I think that is kind of a waste.
If you divide the pull into three sections, the first will be sourish, the second sweet and creamy but without much character, and the third weaker and bitterish.
You control bitterness as a matter of course by cutting the shot when the stream goes light.
You can control sourness in exactly the same way, let the first second of the flow go into the drip tray, then insert your cup. This is an Italian Barista trick back from lever days, when they preinfused until a few drops emerged -- these went into the drip tray, the cup went in only when the stream got creamy. Some people use this trick as a matter of course, since it also reduces the roughness one gets from the grinder fines.
Alternatively, you can flush a little less before the shot and hit the puck with very hot water. This will deaden the acidity a little. However, this only works for the first shot. If the sour/bitter/sweet balance of the shot is wrong for a blend you normally use, adjust your pstat (up to reduce sourness, down to reduce bitterness).
Posted Mon Sep 6, 2004, 1:09pm Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
Thanks for your excellent post Dan! You probably hear this lots, but you are certainly an asset to the espresso community!!!!!
I've noticed the symptom described from time to time on my E2K - but usually this is from filling up the double basket to max capacity, then pulling a short shot from it. The result of this is a shot composed mostly of the compounds extracted at the beginning - and the taste: sour!!! When doing this, I now omit the first 3 seconds of the shot, and the sourness would be gone.
So could it be a matter of the type of compounds extracted in the initial 5-6 seconds, or would it more likely be the temperature hump, or both?
Also, regarding the 30 second wait, if one pulls a blank shot into their empty cup, remove PF, wipe dry, grind, tamp... should this not be an adequate post-flush wait?
Posted Mon Sep 6, 2004, 1:26pm Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
I see that Jim, as usual, has provided an excellent explanation of the taste characteristics in the "test of thirds." I recognize that chart from the SCAA consumer espresso lab, which unfortunately we never heard him present due to technical difficulties. Maybe next year?
As you suggest, the "pause" that I mentioned is easy enough to integrate into your routine without much conscious thought. It simply means not dilly-dallying in front of the grinder or flush-and-locking in rapid succession. Keep in mind, however, that this is specific to prosumer E61s. The cooling flush requirements for other HX machines, like for example the Cimbali Junior with its huge HX, are quite different.
Posted Mon Sep 6, 2004, 1:48pm Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
I haven't tried draining the first seconds of the shot but the idea makes sense. I've been doing a lot of experimentation with my (almost) three-month old Valentina. Someday I may even get a review written. I like the time/volume graph. Any way to access more info like that?
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Mon Sep 6, 2004, 4:22pm Subject: Re: How to Minimize Sour Taste at Beginning of the Pull?
HB Said:
...
I'm still working on it, but so far, the ideal pause time for most of the E61s I've measured is somewhere around 30-45 seconds. It is certainly less than one minute, although I've yet to do systematic measurements. I don't know your particular machine -- a quick test would be to slow your pace by about 25%. That will spike up the HX hump and should eliminate any question of low initial temperature being at fault.
I must of missed it -- you've correlated "the hump's" size to the shot's taste! So Michael Teahan was right, a bit of a hump is good? But it's not flush length, but wait time that determines it?
Damn, now I'll have to resist the urge to run out and buy a multichannel datalogger!
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