Do ultra precise brew temperatures really matter? - Page 3

[timo888]

We are referring to the same "equation" as the graphs I posted from the book describe your quote from Illy. I am referring to the 2nd edition in which Chapter 7 has the information you are referring to in Chapter 8.

If you don't have the book handy, you can fo a "google" on 'Espresso the Science of Quality' and Amazon will let you search the pages for "pressure." Send me an email at erics@erols.com and I will send you my explanation of the equation as it is beyond the scope of this topic.

You're right to remind me that this thread is not about pressure but temperature. I've had some very delicious espresso from Terroir, brewed at ~195°F —where the temperature chart above has a Mr Yuck icon. Terroir was recommending that relatively low temperature, though I cannot find the page at the moment. Illy gives a wide acceptable temperature range. Clearly, one narrow temperature range does not fit all roasts and blends.

But I suspect that all of these variables are interdependent; the practical conclusions we might draw about the effects of temperature under one pressure profile might not be as relevant for others. A long preinfusion, for example, or a short one, might bring out different flavors, even if both pucks are subjected to the same temperature profile.

Regards
Timo

[barry]

FWIW, I have an idle LM 4group that is scheduled to have dual PIDs installed this summer. Not sure when I will get to that as we are putting the finishing touches on a new bakery and bagel kitchen. It will be kicking my butt for a while I'm certain. But, when the machine is done I will offer it up for such a test. It is one big muthah. I'd need someone to arrange moving it to wherever the testing takes place. Maybe a road trip from someone.

To make it even more fun, I could put the real-time brew temp probes in it.

[bernie]

To make it even more fun, I could put the real-time brew temp probes in it.

Alright! In the vernacular of the under 50 set I believe I am "down" with that idea. I'll duct tape the 4group to the top of my wifes Merc Gran Marquis. She will be heading to Kansas City for a 90-day consulting gig. If you could arrange to meet her with some goo-b-gone type stuff to get the duct tape remains off the roof that would be great. There shouldn't be a bug-splatter problem this time of year, but you may want to invest in a bottle of salt-spray remover. Those midwest snow blizzards can make a mess out of an exposed LM.
Bernie

[barry]

The first thing that comes to mind is the effect of the exposure of the dry puck to the heat of the group head once the pf is locked. At what point does the difference in one degree F. increments become less of an impact than that dwell-time? If I look at it in terms of percentages the difference between 199F and 200F is one-half of a percent. But if you look at the dwell time of exposing the dry puck to the group head of just a couple of seconds the difference can be 200 percent. Is exposing the puck to a temp of 200F for twice the amount of time as important to consider as one-half percent difference in temperature? It seems so to me.

I tested this a few years ago... pulling numbers out my ass, iirc, the top surface of the puck took about 30 seconds or so before it exceeded 100F. I was playing with the "immediate brew" requirement in the competition rules. Data is around here someplace. The tests should probably be re-run in my copious spare time.

[barry]

I'll duct tape the 4group to the top of my wifes Merc Gran Marquis. She will be heading to Kansas City for a 90-day consulting gig. If you could arrange to meet her with some goo-b-gone type stuff to get the duct tape remains off the roof that would be great.

If you rent a car and pay for the insurance, then you can just peel the duct tape off and not even worry about taking some paint with it!





Did you ever meet Sammy Olivieri?

[Navin]

If I look at it in terms of percentages the difference between 199F and 200F is one-half of a percent.

As far as I can tell, it doesn't make much sense to talk about percent change in temperature this way when the 0 point of the Fahrenheit temperature scale is arbitrary.
This is really not very relevant to the discussion, but I couldn't restrain the pedant within me.

Navin

[Matthew Brinski]

I quoted this from another thread, Barefoot Espresso Bigfoot found here: http://www.home-barista.com/forum...bigfoot-t6187.html

I posted it here so as not to hijack the subject matter of the original thread.

The emphasis was added by myself -

Anyone else try Bigfoot. I bought a couple pounds the other week for the first time. I was getting good shots from it and it was definitely chocolaty. But about halfway through the pound and decided to try upping the temperature by .6F on the GS3 and wow! Chocolate really came through, especially in milk. It was a bit heavy for espresso, but It was like having a Mocha Latte in milk.

My wife doesn't get impressed by espresso very often, but she was genuinely amazed. I was actually suspicious for a moment that they had substituted some cocoa beans in the blend, but I reminded myself that it would have gummed up my grinder.

That was definitely something unexpected from an espresso blend. Definitely worth trying again.

I find this statement interesting because many individuals have resigned themselves to accept that temperature is not as important as it was conveyed to be a couple of years ago, and several statements have been made regarding that most people are unlikely to taste a temperature variance of less than two to three degrees F.

My first questions go to Robert - Was this change in taste profile repeatable for subsequent shots? Also, do you feeling that your dosing and distribution are consistent? I'm not trying to be critical of your skills, just wondering if another factor is responsible for change in taste profile.

To Greg Scace, Andy Schecter, Barry or any other espresso PhD's out there - does anyone know what the error limits of the GS3 electronics are, or is that proprietary stuff that we just won't know? I'm just curious if a change of 0.6 degrees F can actually produce a change of 1.5 or 1.8 degrees (or whatever).

Matt

[AndyS]

I find this statement interesting because many individuals have resigned themselves to accept that temperature is not as important as it was conveyed to be a couple of years ago, and several statements have been made regarding that most people are unlikely to taste a temperature variance of less than two to three degrees F.

I think this is extremely blend-dependent. Variation in the taste of Schomer's blends is probably observable at a few tenths of a degree F. A mainstream blend like Black Cat is probably a lot less sensitive.

To Greg Scace, Andy Schecter, Barry or any other espresso PhD's out there - does anyone know what the error limits of the GS3 electronics are, or is that proprietary stuff that we just won't know? I'm just curious if a change of 0.6 degrees F can actually produce a change of 1.5 or 1.8 degrees (or whatever).

Not a PhD, but I don't think the limitation is in the electronics, it's in the swirls and eddys of hot water in the machine. The early GS3 prototypes that Greg and I tested in 2005 were marginal when it came to pulling consistent shots at 0.5F accuracy. Presumably the production versions do better.

[hbuchtel]

I think this is extremely blend-dependent. Variation in the taste of Schomer's blends is probably observable at a few tenths of a degree F. A mainstream blend like Black Cat is probably a lot less sensitive.

Just thinking here, but it is unlikely that taste changes relative to temp occur regularly.. meaning that going from 198F to 198.3 could produce a more noticeable change then going from 198.3 to 200, for example, or that a particular flavor is only produced at 200 while others can be brought out by anything within the normal temperature range... thoughts? (or better yet, experiences? )

Henry

[CafSuperCharged]

Presumably some blends (like David Schomer's for example) are more temperature sensitive than others. But no one (to my knowledge) has published a legitimate blind tasting experiment showing that 1F differences are detectable, much less 0.1F differences.

Guys,

Interesting to see how the thread develops into discussions about laws of physics.

The question remains ...

Personally, I do not have the resources to do implied tasting experiments, but would expect them to be revealing of at least some discriminatory capacities in coffee tasters.

Some of the physics part of the debate, I would say the following about:
- if you want a 1F or 0.5F precise/stable espresso machine, what should be your regulation precision requirement? I would say in the 0.1F range.
- does it matter if 198.3F is exactly 198.3F, or your measurement instrument is able to exactly measure that number? No, it only matters it has very precise repeatability. Your Fluke may tell 197.8, and that is not a problem as long as it does give that number each time the temperature is the same value, time and again.
- does a PID help you get your shot at exactly the temperature read on the PID? There likely is a big difference in inter-shot and intra-shot stability between a 1.5 liter boiler pro-sumer machine versus an 11 liter boiler commercial one. Saturation of the group will no doubt be a discriminating factor as well. I think.

So, before setting up a (double? blind?) tasting experiment, these factors need to be controlled.
Having tracked this forum, I know some of you are well able to do that.

It would really be interesting to see what these some of you would experience in this desired tasting experiment.

Regards,

Peter
Netherlands

[roblumba]

I was just pointed out I had a open question about the .6 degree change that I claimed to have tasted.

A double blind taste test would definitely be a good idea. I'm probably not the one to organize it considering that I have little experience in tasting, I don't know how to document things like that.

On several ocassions, when I do change the temperature, I've noticed the change in taste. And usually I change by at least .6F, sometimes .9F or 1.2F or more. But usually I can tell if I've gone a little too far, and reducing by .6F can make a big difference in my opinion, especially when it's just a little too low or too high.

I keep the shot volume and extraction time fairly consistent. Usually around 28-30 seconds at 1.75 ounces. I've been using the Naked Portafilter and the standard double spout. In checking with the naked portafilter, I see a fairly consistent pour. Granted, not textbook pours, but nonetheless after watching several dozen, they are very close to the same.

I reproduced the chocolate intensity on two consecutive days, but this was at the end of the lb. So it's hard to say if rest time after roast had anything to do with it, but it seemed that the chocolate came out at the same time that I upped the temperature .6F. Perhaps it was a combination of roast rest time and the temperature change.

Actually, I pulled out some Bigfoot Espresso this morning and I actually forgot to adjust the temperature up again. The chocolate notes are not really there right now. I'll try it again this morning and see if I can repeat it from Bigfoot that has been sitting in the freezer for a couple weeks.

[roblumba]

Well, the chocolate wasn't as rich this morning, although I still noticed a pleasing difference when moving the temperature up .6F. I think my dose, extraction time and volume where not the same this time. It was a slightly faster flow rate and I allowed a little more of the blonder portion of the shot to come through and I think that took away from the chocolate. I did 1.75 ounces in 26 seconds and I'm guessing something more like 1.5 ounces in 30 seconds will get the intense chocolate. Nevertheless, I still feel the .6F brought it closer to the chocolate and the aromas were a different and pleasing too.

I wonder if the defrosted nature has anything to do with it. It seems that the shot is behaving a bit different than the fresh beans. It starts out going slow, but around 15 seconds into the shot, I get what seems like an unusual increase in flow rate and bubbling coming out of the double spout portafilter. I don't remember that happening with the fresh beans.

Looks like I might need some more experience and time to fool around with this blend to get the chocolate again.

[gscace]

What I don't know is whether current equipment can reliably produce shots at repeatable temperature differences of 1 degree F. That would absolutely need to be established before any tasting studies could go forward. Assuming the equipment can do this, then one could test the potential of some tasters to detect this difference. Any brew temperature difference below 1 degree F probably cannot be accomplished with current equipment on a repeatable basis, and you'd have to count me as a doubter on that until I am proven wrong (which I'll acknowledge when I am).

ken

I have the data to prove that this is possible with some current equipment. Unfortunately I'm not allowed to say more than that. Hope that is good enough for you.

-Greg

[Matthew Brinski]

Not a PhD, but I don't think the limitation is in the electronics, it's in the swirls and eddys of hot water in the machine.

Yeah, I have given some thought to physical limitations such as inlet streams, element size (physical and wattage), volume, probe placement, horizontal vs vertical boiler construction, etc. etc,. Outside of limited adjustment of probe placement though, it's all just that ... thought. I don't have the skill, materials, advanced understanding of physics, or motivation to tackle such ideas. The few individuals who possess some understanding of these things are those who aren't allowed or willing to disclose such information.

Anyway, point well made. I should be asking if anyone has numbers regarding the brew temp repeatability and error limits of the production model GS3 via Scace device. I'm just curious how meaningful a 0.3F or 0.6F change in temperature is from an accuracy standpoint.

I'm just gonna have to buy one.

Matt

[Matthew Brinski]

Well, the chocolate wasn't as rich this morning, although I still noticed a pleasing difference when moving the temperature up .6F. I think my dose, extraction time and volume where not the same this time. It was a slightly faster flow rate and I allowed a little more of the blonder portion of the shot to come through and I think that took away from the chocolate. I did 1.75 ounces in 26 seconds and I'm guessing something more like 1.5 ounces in 30 seconds will get the intense chocolate. Nevertheless, I still feel the .6F brought it closer to the chocolate and the aromas were a different and pleasing too.

Robert,

Thanks for the reply with the details. It's the details of dosing, distribution, and extraction ratio that I give thought to before automatically attributing a taste change to a minor temp adjustment. However, when discussing the notion of just how relevant the importance of temp stability is, most people are over it ... I'm not.

I have the data to prove that this is possible with some current equipment. Unfortunately I'm not allowed to say more than that.

I knew that response was coming ... quite understandable though. Thanks.


Matt

[roblumba]

When you say, most people are "over it" do you mean that they have accepted temperature stability as a relevant factor? That's my understanding. I'm a bit surprised there are people who don't believe it.

[Matthew Brinski]

No, I believe that most people understand that temperature matters. However, it seems that most believe that temp profiles repeatable to the precision of 0.1 to 1 degree F aren't of great consequence. They may be right, but I am not so sure.


Matt

[roblumba]

I can agree that .3F is perhaps such a small difference that is perhaps undetectable. I usually change by .6F when I'm exploring the temperature space because .3F doesn't seem to be much difference to my taste. Nevertheless, I sometimes inch the temp up by .3F when I feel like I don't want .6F change, but just to give it a hair nudge in one direction or the other.

[cafeIKE]

No, I believe that most people understand that temperature matters. However, it seems that most believe that temp profiles repeatable to the precision of 0.1 to 1 degree F aren't of great consequence. They may be right, but I am not so sure.

It's not that temperature precision is not relevant, it's just bleeding hard to achieve.

For example : take a pot of boiling water and stick in a half dozen calibrated probes at various points. Variance will exceed 0.1° several times over.

Espresso is a collection of plusses and minuses.
The age of the coffee, grind, dose, distribution, brew pressure, water temp, shot volume, not necessarily in that order.

Add in the cup temperature, geometry, interval between pull, consumption and temperature.

To reliably test temperature effect, one must minimize all of the other variables.

If you bump up the temp and love the taste is it because the humidity is up and the grind is off a bit, the coffee is a bit new / old, the dose is 15.5 instead of 15 or the cup is 5 degrees warmer / cooler? ALL? None?

As long as the espresso is damn fine and the annual sink shot is a result of forgetting to reset the timer, I'm good to go.