I hope to get as many people discussing this as possible. So, please feel free to put in your two cents...it's worth more than that to me!

I think the mainstream assumption is the flatter the temp profile during a given shot, assuming all other parameters are already as good as it gets, the more better the taste. But is it that way?

Since there is a variety of machines due to the variety of forum users, I've created different questions to make this discussion involve more people. So not all questions may apply to you, but please respond to any one you wish. If you're not sure about your machine's brew temp profile, feel free to participate with as much as you know. I'm aware of the other variables, but assume the dose, grind, bean freshness, quality, etc, is all the best.

1. To those who know their machines have a very flat intrashot temp within 0.5-1.0 degrees:
When you have been able to accomplish and enjoy a flat-temp shot, whether by purchasing an expensive, well designed machine, or using PID, or modding a cheaper machine, how did the taste compare to earlier experiences when you had a comparable blend brewed "competently" on a machine with a declining (or increasing) shot brew temp of greater variance? Was it worth whatever the cost and effort was to get the temp flatter?

2. To those who have a mid-level shot temp profiles within 2 degrees:
Do you think you get the very best shots you've had from your own machine, or do you wish to either modify your existing machine, or upgrade to a "flatter temp profile" machine?

3. To the rest of us whose machines have temp profile variances greater than 2 degrees:
I'm lumping us all together because I'm assuming we all think the same thing..."we could get better shots than what we're getting right now".
First, is that actually true for you? If you've enjoyed shots from higher-end machines, enough to know the difference, do you think they were better?

4. And to everyone:
Do you prefer a shot from a very flat temp profile machine, or do you actually prefer a declining or increasing temp profile? Why?
Feel free to share your experience-informed opinion on brew temp profile.

Lots of views and zero replies...

Has anyone experienced a consistent taste difference between shots pulled from a very flat machine, compared to say single boiler machines with 5-10 degree temp drops during the shot pull? What is that taste difference?

Does a flatter temp profile taste more complex, or more bland?

If you have a LaMarzocco, any dual boiler machine, Alexia, La Peppina, Caravel, or know your machine's temp profile is very flat: your tasting experience replies would be especially greatly appreciated!

If you consider yourself to be a cupper, taster, or diehard, your replies also would be wonderful!

I use an open boiler lever machine with a declining temp profile of around 7 degrees from start of preinfusion. No complaints here. I think the machine excels at light roasts. I don't have a temp stable machine to compare with, though, and there are so many other variables... probably will see more discussion around this with the release of the DE machines where you can program the temp profile you want.

Can you describe what difference your shots have compared to other machines? Are the flavors more distinct, complex?
Or is there some other taste characteristic that you can put your finger on that is why you think light roasts are better tasting than with other machines (including not so stable ones)?

I really cannot answer your question as to why the temp profile in machine is better or worse than another. I think because there are so many variables and most people, myself included, don't have multiple high end machines of different kinds at their disposal to do rigorous sbs comparisons it's a hard question to answer. I, again, think machines like the soon-to-be-released DE+ will be able to better enable home baristas to start tackling questions around temp profiles.

Just my thoughts, and I am far from the resident expert around here.

Part of why the response to this post might be slow is that there is lots of info already available around this site if you care to search for it, so people may feel like it has been discussed to death. A couple of entry points include:

Dan's video exploring the differences between HX and DB temperature profiles, with a side-by-side taste comparison:

Newbie Introduction to Espresso - Heat Exchanger vs. Double Boiler Espresso Machines [video]

Jim's video review of the Bezzera Strega, which features a declining temperature and pressure profile (as is typical of commercial-group spring-lever machines): Bezzera Strega - Second Look

My own experience has been that shot temperature repeatability matters much more than intra-shot temperature stability. One thing many buyers overlook is that the coffee puck itself is a heat-sink, so that a flat temperature of water exiting the brew group may actually yield a rising temperature profile in the puck itself. As for the impact of different temperature profiles, this is hard to isolate from other variations between the designs of different machines, but I will say that I find lever group shots generally preferable to those I get from pump machines, despite (or in part because of?) their lack of intra-shot temperature stability.

I guess I'm after multiple anectodals...I have looked a lot, and haven't seen people really discuss their taste experiences with different temp profiles.
"It tastes better" isn't really describing differences to me. I'm drawn to why someone says they taste subtle notes they didn't notice before after making a change of some kind.

As far as machines go, isn't pressure profile is really the only other variable, other than global stability?
The rest of course is the human factor with dosing, grinding, tamping, distribution, etc. So, at some point along the upgrade scale the pressure and temp stability hit a ceiling, and manufacturers have to add convenience features, shot to shot time, and changeable profiling (and shiny looks) to add value.

So, is the taste difference between a lever and HX to you a matter of say, complexity enhancement, or is it just apples and oranges different?

I guess while it helps create consistency to allow focus on other variables, the flat temp profile is portrayed as the holy grail for taste. Has that really been people's experience?

Thanks for posting those other threads, BTW, very informative!

[creative nickname] wrote:My own experience has been that shot temperature repeatability matters much more than intra-shot temperature stability. One thing many buyers overlook is that the coffee puck itself is a heat-sink, so that a flat temperature of water exiting the brew group may actually yield a rising temperature profile in the puck itself.

+1

I agree on both points. Consistency is the holy grail of espresso machines and grinders. I don't believe that swings of a few degrees one way or the other during the shot result in material differences, as long as those same swings occur on every shot. It may be harder to achieve this consistency on an HX machine if the flush technique varies (i.e., the human factor could result in significantly different temperature profiles shot-to-shot.) That's part of learning to use an HX machine. Some designs, like a single-boiler non-HX without PID, make it hard to keep the temperature profile consistent, and can produce extreme temperature swings that significantly affect taste -- like under-extraction, over-extraction or even "cooking".

In general, double boiler machines make it easier to achieve consistency, stability and fast recovery time, especially saturated group designs like the GS/3. That said, my GS/3 rises about 2.5 degrees from idle during the first 10 seconds or so of the shot, then stays incredibly flat thereafter -- within 0.1-0.2 degree or so. This happens even if I flush for a few seconds and allow the temperature to recover before pulling the shot. The profile is very consistent. While consistency and stability are important byproducts of the saturated group design, my guess is that the real selling point is fast recovery time -- something very important for busy cafes.

Personally, I have a hard time detecting any difference in taste due to small (1-3 degree) temperature changes. Unless you're a super-taster, I think temperature is one of the least important variables, provided you stay in a range of about 195F-205F. Much lower, and under-extraction is a possibility. Much higher, and you'll either over-extract or cook the coffee. Many just settle on 200F and leave it there for all coffees. Sometimes I increase the temperature a few degrees for a really light roast that's hard to extract. I rarely, if ever, go over 203F. I might bring it down to 197-198 for a dark roast if I'm getting bitter notes. The effects are pretty subtle.

Frankly, changes in grind, dose and/or pull time (brew ratio) have much more profound effects on taste, and consequently those are the variables that deserve the most attention. As long as your machine produces a reasonably consistent temperature profile, you'll be OK.

Peppersass wrote:...I don't believe that swings of a few degrees one way or the other during the shot result in material differences, as long as those same swings occur on every shot...Personally, I have a hard time detecting any difference in taste due to small (1-3 degree) temperature changes. Unless you're a super-taster, I think temperature is one of the least important variables, provided you stay in a range of about 195F-205F...Frankly, changes in grind, dose and/or pull time (brew ratio) have much more profound effects on taste, and consequently those are the variables that deserve the most attention. As long as your machine produces a reasonably consistent temperature profile, you'll be OK.

Do you have an opinion on taste on a flat temp shot vs declining temp shot?

I understand taste pleasantness is subjective, but I think taste differences should be discernible among a given group of people.

For example, a group of people ought to be able to agree that one shot is nutty and chocolaty without any fruit notes and therefore somewhat basic, while another shot might be distinctly complex with changing flavors, whether fruity, spicy, or herbal. While they may not agree on the details, they can agree that one shot is "simple" or "flat" and the other is "complex".

So, do people experience a more complex, or a more simple taste with a flat temp profile?

I saw where another_jim posted that a declining temp seems to have less bitterness, and maybe more complexity due to the extraction rate dropping off as the temp drops off. This makes sense with the extraction thirds concept. Has this been consistent with everyone's experience?

crispie wrote:I guess I'm after multiple anectodals...I have looked a lot, and haven't seen people really discuss their taste experiences with different temp profiles. "It tastes better" isn't really describing differences to me. I'm drawn to why someone says they taste subtle notes they didn't notice before after making a change of some kind.

Lever shots, as a class, tend to be sweeter, with more clarity, and often a bit less body than pump machine shots (although a machine with a very strong spring like the Strega can give you back most of the body without losing the sweetness and clarity). There will be variations from machine to machine, obviously, and it is anyone's guess how much of the difference comes from the temperature profile and how much from the pressure profile. Ideally it would be nice to be able to isolate just temperature's impacts, and to see how that variable might interact with different pressure curves as well. But no existing machine gives that level of control. The Decent Espresso machines are intriguing in part because (according to the company) they use water mixing in combination with a real-time sensor reading at the puck to allow precise control over temperature intra-shot. You will probably get better answers to your question once those are out in the wild and people can play with them. And if this subject is of particular interest to you why not get one yourself and do some of your own experimenting?

crispie wrote:As far as machines go, isn't pressure profile is really the only other variable, other than global stability?
The rest of course is the human factor with dosing, grinding, tamping, distribution, etc. So, at some point along the upgrade scale the pressure and temp stability hit a ceiling, and manufacturers have to add convenience features, shot to shot time, and changeable profiling (and shiny looks) to add value.

There are lots of variables at work beyond temperature and pressure. There is the amount of turbulence in the water flow and the smoothness of its dispersal across the puck. There are variations in basket shape (see, for instance, the very narrow basket used in the VAM/Arrarex Caravel). There are variations in the amount and quality of feedback given by the machine to the user. All of these may matter in terms of real-world shot quality and consistency.

crispie wrote:So, is the taste difference between a lever and HX to you a matter of say, complexity enhancement, or is it just apples and oranges different?

Apples and oranges might be going a bit far; it's all still espresso, after all! There are pump machines that let you control pressure profiles, and even simple pump machines can yield very tasty shots if driven well. But on average I prefer levers, for the reasons I gave above. Additionally, one of the strongest benefits of levers is that they reduce the likelihood of really bad shots -- although not every lever shot is perfect, I've had far fewer shots from lever machines that were so far off that I didn't want to finish them.

crispie wrote:I guess while it helps create consistency to allow focus on other variables, the flat temp profile is portrayed as the holy grail for taste. Has that really been people's experience?

I got rid of my very-temp-stable Breville Dual Boiler within six months of getting my first lever machine (a Caravel) and I've never looked back or regretted that decision. So I'd definitely come down on the side of "not the Holy Grail."