Titan Grinder Project: Does burr heating coffee grounds negatively affect taste of espresso?

Grinders are one of the keys to exceptional espresso. Discuss them here.
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cannonfodder
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#1: Post by cannonfodder » Jun 08, 2007, 10:34 pm

I wanted to get some temperature measurements from both grinders while I have them. While heat buildup in a home environment is a non issue, I still wanted to check it. So I loaded up the Kony and Super Jolly with a half pound of coffee to run a sustained grind test. Both grinders are dialed in for the same extraction rate. My results were anticlimactic but I have decided to post them as part of the collective information.

I started with the Kony. I placed a type K thermocouple deep in the grinder chute and another in in the hopper suspended just above the burrs. I took particular care to make sure the thermocouple in the grind chute was suspended and centered in the grind discharge chute, centered between the burrs and chute face.

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The Kony produced an unremarkable temperature curve topping out at 96.1 degrees Fahrenheit. The curve was a little choppy possibly due to the slower grind speed resulting in warm spots in the grinds. The temperature above the burrs actually dropped during the grind session. It was a hot day in Ohio so the air conditioner was running. The bean temperature was warmer than the ambient air temperature as shown in the graph. As the grinder chewed up the beans, it drew the cooler air down through the beans and the reading actually dropped as the grind progressed.

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Once I keyed in the plot data I moved on to the Super Jolly.

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I used the same configuration but with one important note. The beans have stabilized to the ambient air temperature. To properly compare the temperatures, you would need to add almost 5 degrees to the Super Jolly temperatures.

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Once again, this is un-dramatic information. The Super Jolly grinds faster and the burrs rotate substantially faster. The Super Jolly also transfers more heat to the coffee while grinding. Again, in a home environment this is a moot point.

The delta between the two grinders is so low I doubt that temperature plays much part in the cup difference.
Dave Stephens

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RapidCoffee
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#2: Post by RapidCoffee » Jun 08, 2007, 11:28 pm

cannonfodder wrote:I wanted to get some temperature measurements from both grinders while I have them. While heat buildup in a home environment is a non issue, I still wanted to check it. So I loaded up the Kony and Super Jolly with a half pound of coffee to run a sustained grind test. Both grinders are dialed in for the same extraction rate. My results were anticlimactic but I have decided to post them as part of the collective information.
...
The delta between the two grinders is so low I doubt that temperature plays much part in the cup difference.
Dave, thanks for running this experiment. I think you've just posted some very valuable results. Given the small temperature rise (perhaps 10F to grind a shot, based on my SJ timings) and the small differences between the two grinders, we can probably rule out grinds heating as a major factor in home use. This allows us to concentrate on parameters other than temperature that distinguish grinder performance.

Nice work!
John

Ken Fox

#3: Post by Ken Fox » replying to RapidCoffee » Jun 09, 2007, 12:31 am

Something tells me that some myths are being progressively debunked :mrgreen: :mrgreen: :mrgreen:

ken
What, me worry?

Alfred E. Neuman, 1955

Matthew NB

#4: Post by Matthew NB » Jun 09, 2007, 8:55 am

RapidCoffee wrote:Dave, thanks for running this experiment. I think you've just posted some very valuable results. Given the small temperature rise (perhaps 10F to grind a shot, based on my SJ timings) and the small differences between the two grinders, we can probably rule out grinds heating as a major factor in home use. This allows us to concentrate on parameters other than temperature that distinguish grinder performance.

Nice work!
Only, one could imagine that as of a certain temperature point, the increased heat has an effect on the taste in the cup.

Now, how do you know:
a) what that temperature point is,
b) the 10F (=5.5556Celsius) difference ends up before or after that point.

So I wonder whether the fact that the difference is "only" a 10F is enough to support the conclusion that heating is not a factor. :)

This may be nitpicking but reading these threads here, I definitely get the feeling this is quite common and accepted here so hence my post... :lol:

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Walter

#5: Post by Walter » Jun 09, 2007, 12:02 pm

Ken Fox wrote:Something tells me that some myths are being progressively debunked :mrgreen: :mrgreen: :mrgreen:

ken
Now aside from the fact that "myths" - in the original sense of the word mythos - were much closer to reality than the so called "facts" we describe in our languages based on logos as a tool of communication I see no debunking of anything so far. But what I do seem to sense is a certain number of hasty conclusions based on questionable experiments.

If it is agreed upon, that the heat we notice comes from the fraction of the beans - meaning from inside the beans rather than the environment outside, I don't see why it should be a "moot" point that this very heat is capable of doing considerable damage to the overall taste, namely by affecting the volatile components as well as those which undergo substantial chemical changes when heat is applied, just because we don't notice any "dramatic" temperature rise in the environment relatively far away (where the thermocouples actually sit, surrounded by mostly air which happens to be a pretty good thermal insulator).

If I were doing such experiments with a claim of them being remotely scientific, I would probably first try to figure - or measure properly - how much energy in form of heat - on a microscopical level - is actually released and how this heat would affect the chemical substances in the close vicinity (at least those we know of). And then I would try to find out if either type of grinder - conical or flat - does less thermal damage than the other...

But then again, what do I know... :lol:

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RapidCoffee
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#6: Post by RapidCoffee » Jun 09, 2007, 12:25 pm

Matthew wrote:Only, one could imagine that as of a certain temperature point, the increased heat has an effect on the taste in the cup.

Now, how do you know:
a) what that temperature point is,
b) the 10F (=5.5556Celsius) difference ends up before or after that point.

So I wonder whether the fact that the difference is "only" a 10F is enough to support the conclusion that heating is not a factor. :)
Walter wrote:But what I do seem to sense is a certain number of hasty conclusions based on questionable experiments.

If it is agreed upon, that the heat we notice comes from the fraction of the beans - meaning from inside the beans rather than the environment outside, I don't see why it should be a "moot" point that this very heat is capable of doing considerable damage to the overall taste, namely by affecting the volatile components as well as those which ungergo substantial chemical changes when heat is applied, just because we don't notice any "dramatic" temperature rise in the environment relatively far away (where the thermocouples actually sit, surrounded by mostly air which happens to be a pretty good thermal insulator).

If I were doing such experiments with a claim of them being remotely scientifical, I would probably first try to figure - or measure - how much energy in form of heat - on a microscopical level - is actually released and how this heat would affect the chemical substances in the close vicinity (at least those we know of). And then I would try to find out if either type of grinder - conical or flat - does less thermal damage than the other...
Both of you raise valid points. That's the beauty of the scientific method: results get published for others to critique, reproduce, debunk, confirm... and only over time can theories become "established". For practical purposes, I'm satisfied that a global 10F temperature rise is insignificant - otherwise we'd notice significant differences in taste when the beans are ground in an ambient temperature of 80F instead of 70F. But the idea that grinding microenvironments could produce significantly hotter temperature gradients is well taken. If we find significant taste differences between e.g. the Mazzer Robur and Kony, this might be worthy of further exploration. And Walter, I'd be delighted to have you jump in and run some experiments for us! (While you're at it, perhaps you could investigate the impact of humidity as well. :) )
John

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Walter

#7: Post by Walter » Jun 09, 2007, 12:54 pm

RapidCoffee wrote:For practical purposes, I'm satisfied that a global 10F temperature rise is insignificant - otherwise we'd notice significant differences in taste when the beans are ground in an ambient temperature of 80F instead of 70F.
I'm sorry but you've lost me here, I'm unable to see anything that would warrant this conclusion...

My own little hypothesis is that the grinding process per se has a detrimental effect on the taste, so to me the question would be which grinder - or which form of grinding process - does a minimal damage.
And Walter, I'd be delighted to have you jump in and run some experiments for us! (While you're at it, perhaps you could investigate the impact of humidity as well. :) )
Sorry, but I haven't seen the inside of a lab for some 25 years now, hence I'm afraid I won't be able to help you out with that... :)

Java Man

#8: Post by Java Man » Jun 09, 2007, 1:05 pm

Walter wrote:My own little hypothesis is that the grinding process per se has a detrimental effect on the taste, so to me the question would be which grinder - or which form of grinding process - does a minimal damage.
Well, if we could just pull a few shots with unground beans, we may be able to test that one! :wink:

Rick
Java Man
A.K.A. Espressopithecus

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RapidCoffee
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#9: Post by RapidCoffee » Jun 09, 2007, 1:51 pm

Walter wrote:My own little hypothesis is that the grinding process per se has a detrimental effect on the taste, so to me the question would be which grinder - or which form of grinding process - does a minimal damage.
Do you believe the detrimental effect is caused by heating of the grinds? I doubt that a 10F rise in temperature (measured by Dave) has an impact on taste. But it's certainly possible that microenvironments created during grinding will subject the grinds to much more heat, enough to degrade volatile flavor components in the coffee. Any detrimental effect must be dramatic enough to operate within a very short time frame, since the beans are only in contact with the burrs for a few seconds. I'm not sure how you'd go about testing for this. Perhaps an IR thermometer?

EDIT: It occurs to me that there is a low-tech way to test for grinder-based heat degradation. Dave's temperature graph shows the grind temperature rising for the first 70 seconds. It's reasonable to assume that heat degradation, if present, gets worse with increased grinding time. Grind a hopper full of beans for at least a couple of minutes, dosing as you grind. Pull shots and see if you can taste any change between the extractions.
John

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Teme

#10: Post by Teme » Jun 09, 2007, 10:43 pm

RapidCoffee wrote:Do you believe the detrimental effect is caused by heating of the grinds? I doubt that a 10F rise in temperature (measured by Dave) has an impact on taste.
I agree with Walter in that this should not automatically be dismissed. If we have people (as we do) who claim to be able to taste differences of even 0.2C in brew temperatures, we should also accept that there is a possibility that a temperature difference of this magnitude (of more than 5.5C) in the ground coffee could also make a difference. This would be pretty hard to measure and confirm, though.

Br,
Teme