Consistent brew temperature required for exceptional espresso - Page 4

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cpreston
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#31: Post by cpreston »

Dick,

Sent you a PM.

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bostonbuzz
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#32: Post by bostonbuzz »

But... are there any machine that don't produce a consistent temperature profile, assuming enough time between shots? I don't think so... Are there machines that drop +10 degrees intrashot? Yes. But nobody in this discussion has one, or uses a scace with one (krups??).

The discussion is really about what temp profile is best. This is too difficult to answer at this time, and likely is coffee dependent.

Let's start with, "What is the threshold temp profile makes all coffees worse?" Get different machines with the same grouphead size, baskets, preinfusion times, but different temp profile and do a zillion double blind tests. Further discussion until then is not productive.
LMWDP #353

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#33: Post by Anvan »

bostonbuzz wrote:But... are there machines that drop +10 degrees intrashot? ... The discussion is really about what temp profile is best. This is too difficult to answer at this time, and likely is coffee dependent. ...
I'm pretty sure you're right, John, but the point was never to evaluate machines with 10-degree fluctuations - as you ask, who would care?

But I don't remember anyone ever proposing - even in the most general way - how upward or downward temperature changes during phases of espresso extraction affect the results. I believe this was Jim's point and challenge with his three profiles. The exaggerated experiment proposed is only a rough attempt seeking any overall rule of thumb there might be, such as we use now with "too cool = sour."

That one at least seems to be a generally accepted coffee principle ("GACP"?) but it's one-dimensional, considering only one temperature and its effect evaluated over the entire end result. In calculus terms, adding the time dimension here would make any new results analogous to the integral of that rule.

Which coffees benefit how much given how much change? Who knows - but without first having even the most basic understanding, we regardless can't jump to that level of precision.

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another_jim
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#34: Post by another_jim »

Holy cow; Antony is right: this experiment is doable:

-- Use one of the newer brew-boiler per group machines with three groups set to 197, 200, and 203
-- Get one Schectermatic shot cup set
-- run the groups simultaneously, move the cups between groups to achieve the desired profiles, and serve.
-- if people can learn to ID the profiles blind, we have a winner. Eventually people who could tell the profiles apart would also be able to describe the way they taste different.

So I retract the crack about this being a senseless debate in all possible worlds. However, I still strongly doubt that anyone could actually succeed in learning to distinguish the profiles
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HB
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#35: Post by HB »

Seems we're all on the same wavelength; I just posted this to my Google+ page (where I tend to post my half-baked ideas :lol:):
HB wrote:Another perennial debate of the merits of flat vs. rising vs. falling brew temperature profiles is now in progress in the forums:

Consistent brew temperature required for exceptional espresso

Although there's been talk of espresso machines capable of temperature profiling in the past (e.g., Rancilio xCelcius at the 2011 SCAA conference), I'm not aware of any production model offering the same level of control available for pressure profiling (e.g., La Marzocco EP, Synesso Hydra). Musing over the matter, I wondered if one could jerry-rig temperature profiling using two groups of an EP. That is:
  1. Run one group at temperature X and the adjacent one at temperature X+n
  2. Run a conduit line between the groupheads.
  3. Install a blind filter in one group so all its output exits via the conduit line into the other group.
  4. Program the pressure profiles such that the majority of brew water is contributed by one or the other group (e.g., by dropping one of the group's brew pressure by 0.5 bar while the other remains at the target setpoint).
  5. To profile a shot, start the two groups at the same time.
For example, to create a rising profile, program the pressure on group 1 to drop 0.5 bar during the last 10 seconds of the shot. When the pressure drops, some portion of group 2's brew water should flow from group 2 to group 1. To create a declining profile, program the pressure on group 1 to start 0.5 below the setpoint of group 2, then rise towards the end while group 2 declines.

Yeah, it's just a thought experiment...
The Schectermatic shot cup set approach sounds less complicated though.
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Marshall
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#36: Post by Marshall »

HB wrote:The Schectermatic shot cup set approach sounds less complicated though.
Maybe. But, as someone who has has one, I think you'd need to hire the Olympic gold medal synchronized swimming team to do it right. And even then, I'm not sure there would be room for the three trays.
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mitch236
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#37: Post by mitch236 »

Not to complicate this further but which machine will you use that provides a consistently flat brew temp? If you want to use a multi group machine and switch between groups during the synchronized shots, you would need to have a machine capable of providing flat temps at each group. My machine varies 3 degrees from shot start to finish. I'm not sure how much of that is because the Scace absorbs heat as the shot starts or if the machine is actually running that way.

Either way, it's an interesting question and maybe one day we will have the answer

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another_jim
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#38: Post by another_jim »

The NS techs could probably trick out a 3 group Aurelia to do this, since each group has a separate HX that can be individually tuned. They'd need to be interested though, since it would take a lot of work.
Jim Schulman

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#39: Post by HB »

mitch236 wrote:My machine varies 3 degrees from shot start to finish. I'm not sure how much of that is because the Scace absorbs heat as the shot starts or if the machine is actually running that way.
I don't know how you're measuring (and I don't wish to derail the conversation on brew temperature measurement techniques), but I follow the WBC Procedure for Measurement of Brewing Water Temperature. I just checked and mine reaches the target temperature within six seconds and holds there within one degree. Assuming you're willing to flush the second group for a few seconds before starting the extraction, I think that's good enough for this thought experiment.
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Peppersass
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#40: Post by Peppersass »

I think it would be worthwhile to know whether detectable differences in taste exist between a flat temperature profile and profiles that vary during a shot, provided that proper blind tasting techniques are used to determine the results.

However, I believe a significant complication for the experiment lies not on the flat profile side, but on the variable profile side. Which variable profile (i.e., machine) do you choose, and how do you separate that characteristic from the machine's other characteristics? Seems like a tough one to me.

Further, if it turns out that a flat profile isn't always superior, and that different variable profiles produce better taste under certain circumstances (coffee, grind, dose, etc.), then I'm afraid we'll fall down a rabbit hole from which there will be no escape. We'll be pushing espresso machine manufacturers to give us control over the temperature profile in a repeatable way, and then our dial-in time will go up exponentially as we try to integrate an infinite number of possible profiles with the other interacting variables. FWIW, I have the same concern about pressure profiling.

I'm all for the scientific approach and exploring cause-and-effect relationships, but when those pursuits lead us far away from practical means for producing an excellent cup of espresso (not necessarily a perfect cup), then I wonder whether the effort is worthwhile.