Chilling Espresso and pH

[malachi]

It's good to see you back in the game Chris. We missed you.

Aw shucks...

BTW, you all should check out the PH of hot versus chilled espresso.

Split from Controlling shot extraction pattern.

[Abe Carmeli]

Aw shucks...

BTW, you all should check out the PH of hot versus chilled espresso.

Please tell, oh great one. What's happening there?

[malachi]

Oh come on... you don't want me to ruin your fun, do you?

[Abe Carmeli]

Oh come on... you don't want me to ruin your fun, do you?

I'm out of test strips but a wild guess says it gets acidic as it cools?

[HB]

Well, I'm going to guess that the loss of carbon dioxide would come into play. Now only if I could remember how that affects pH... I think it goes acidic. Unfortunately I don't own a pH meter. Is this effect something that can be easily tasted, and if so, what's the protocol for a malachi-approved chilled espresso?

[default]

i've a pH meter, what can i do to test it?

[Abe Carmeli]

i've a pH meter, what can i do to test it?

Test the acidity of a shot after it is pulled (hot), then periodically as it cools off until it is at room temperature. Lastly, put it in the fridge for 30 minutes and test it again.

[Dogshot]

I would think this phenomenon has more to do with time than temperature.

[malachi]

Both in my experience.
For example, pull a shot into liquid nitrogen and then evaluate - compare to a shot pulled into a demi and then cooled in a cocktail shaker with an ice cube.

[barry]

i've a pH meter, what can i do to test it?

Test the acidity of a shot after it is pulled (hot), then periodically as it cools off until it is at room temperature. Lastly, put it in the fridge for 30 minutes and test it again.

somewhere in the deep recesses of my mind, something is screaming, "NO! can't do that."

hhrrrmmm.... something having to do with the test solution being around room temp in order for the meter to work properly.

[AndyS]

Both in my experience.
For example, pull a shot into liquid nitrogen and then evaluate - compare to a shot pulled into a demi and then cooled in a cocktail shaker with an ice cube.

Your proposal is a loaded one. No common pH meter, even a "temperature compensated" one, delivers accurate measurements given such wide temperature extremes. Whatever measurements you're getting, they can't be trusted.

[malachi]

Really?
The one I'm using claims:

Range: 1 - 14.00 pH
Accuracy: ± 0.01pH
Temp Compensation Range: -5 - 110C

The only hot liquid I've been testing is the baseline espresso.
I'll double check the temps on the cooled liquids and make sure they're all at the same temp.

[AndyS]

Really?
The one I'm using claims:

Range: 1 - 14.00 pH
Accuracy: ± 0.01pH
Temp Compensation Range: -5 - 110C

The only hot liquid I've been testing is the baseline espresso.
I'll double check the temps on the cooled liquids and make sure they're all at the same temp.

I know they say that, but the reality is a bit ugly compared to the hype. My experience with a $250 probe hooked up to a $150 meter is that you're very lucky to get repeatability within a couple tenths once the temperature starts to vary significantly.

I don't doubt that there's much better equipment out there, of course.

[malachi]

Hmmm...
Honestly I don't know much about this.
The set up I'm using is borrowed and I know it's not cheap (it was strongly suggested that I not damage it) but don't know much beyond that. I guess it's a similar model to the one used by the food scientist on staff at El Bulli, but beyond that....

I'll test the various results (chilled in different ways) each at different temps after chilling to see what I get. And then I'll try and test them all at the same temp.

I've got the set up for another week, so I should be able to get some results.

[barry]

Hmmm...
Honestly I don't know much about this.
The set up I'm using is borrowed and I know it's not cheap (it was strongly suggested that I not damage it) but don't know much beyond that. I guess it's a similar model to the one used by the food scientist on staff at El Bulli, but beyond that....

I'll test the various results (chilled in different ways) each at different temps after chilling to see what I get. And then I'll try and test them all at the same temp.

I've got the set up for another week, so I should be able to get some results.

perhaps check a known reference sample at various temperatures to see how the readings are affected? you are calibrating on a buffer, aren't you?

[malachi]

Yup.
Got good instruction on the use when I borrowed it.

But that's a good point. I should test on reference samples at different temps.

[default]

we do pH test after some roast batches before we send sample to the customer. i saw my colleague cooled down the brewed coffee to a certain temperature before measuring them. i'm not sure whether it could be used with hot espresso.

[brianneary]

Still waiting to here the acidity results. However, for what it's worth, we notice here that iced drinks preserve their flavor best when the hot drink is prepared first - in toto, then poured over ice. For example, make the hot latte or cap first; then chill it. If you just pull the espresso and pour it over ice, then add milk, the result is bitter and loses its original taste. Any thoughts as to why that would be?

[DavidMLewis]

Really?
The one I'm using claims:

Range: 1 - 14.00 pH
Accuracy: ± 0.01pH
Temp Compensation Range: -5 - 110C

The only hot liquid I've been testing is the baseline espresso.
I'll double check the temps on the cooled liquids and make sure they're all at the same temp.

Hi Chris,

You should be able to test that with distilled water. Measure hot, let cool, measure again, then re-heat and measure a third time. If all three are the same, the meter specs aren't lying. There's some possibility, of course, of some CO2 being absorbed and turning to carbonic acid as it cools, and then being driven off again as it heats; you could avoid that by cooling in a nitrogen atmosphere if the first and last match but are less acidic than the second.

Best,
David