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jpender
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Posted Mon Jul 22, 2013, 2:27pm
Subject: Re: Roast and caffeine
 

Netphilosopher Said:

I know that sublimation of caffeine itself is possible during roasting.  I always wondered if some of the funk left behind was deposited caffeine - but it's so small (over prolly a hundred lb or so of coffee and nothing resembling caffeine frost) that I figured it isn't an appreciable amount.   The sublimation temperature for caffeine at 1 atmosphere is well near 350°F or so - again, that takes time to happen.

Posted July 22, 2013 link

Well, there's this:

The occurrence of caffeine in the air of New York city
Dong, M., Hoffmann, D., Locke, D.C., Ferrand, E.
Atmos. Environ., 11, 651, 1977

Abstract
Caffeine was found to be a major constituent of the basic portion of organic particulate matter in New York City. The concentrations of caffeine in two composite samples collected in the period January to April, 1975 were 3.4 µg/1000 m3 and 7.0 µg/1000 m3 respectively. The ubiquity of coffee roasting plants in New York City and adjacent New Jersey may explain its abundance.


Also, in Espresso Coffee, Illy says:

"Caffeine is stable upon roasting, but a small part is lost by sublimation.
Nevertheless this is often overcompensated by the roasting loss."

That doesn't really answer the question though, does it?

Netphilosopher Said:

...based on my schedule I won't get to it until well into 1st or 2nd quarter next year.

Posted July 22, 2013 link

That's okay, I can wait. :o)
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Netphilosopher
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Posted Mon Jul 22, 2013, 5:18pm
Subject: ...
 

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Buckley
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Posted Mon Jul 22, 2013, 6:34pm
Subject: Re: Roast and caffeine
 

Dear jpender,

It is unclear just what you will accept as 'proof' that roasting makes no difference to caffeine levels.  Netphilosopher's contribution concerning the stability of caffeine at roasting temperatures coupled with his meticulous studies of the extraction process, illustrated by his transparency in posting his methods and computations, carries a lot of weight with me.  He could easily publish a bench-science collection of his investigations as essays.  So, he has the potential to have the authority of publication, but he does not carry that imprimatur, currently.  But if it is scientific refereed journal results that will convince you, why don't you just search food science and agriculture journals for yourself?  If I can do it,so can you.  You will find no consistent effect on caffeine levels by different roasting intensities in the following:

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting By Ivana Hečimović; Ana Belščak-Cvitanović; Dunja Horžić; Draženka Komes. In Food Chemistry. 129(3):991-1000 Language: English. DOI: 10.1016/j.foodchem.2011.05.059(the czeck names font does not carry over but the text is in english, not just the abstract, but the whole text.

Antioxidant activity, polyphenols, caffeine and melanoidins in soluble coffee: The influence of processing conditions and raw material By J.A. Vignoli; D.G. Bassoli; M.T. Benassi. In Food Chemistry. 124(3):863-868 Language: English.

Investigation of Optimum Roasting Conditions to Obtain Possible Health Benefit Supplement, Antioxidants from Coffee Beans. By: Sulaiman, Shaida Fariza; Moon, Joon-Kwan; Shibamoto, Takayuki. Journal of Dietary Supplements, 2011, Vol. 8 Issue 3, p293-310, 18p.

And this reference useful if you want to do further research on this question on your own:

Caffeine : A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References By: Parker, Philip M.; Parker, James N. San Diego, CA : ICON Health Publications. 2004. eBook.  Database:    eBook Collection (EBSCOhost)

The 'urban myth' is that roasting destroys caffeine; this has been related to me consistently for the last 15 years.

Concerning the 'roaster tar high', this sounds suspect for the reason that, if enough caffeine were allowed to sublimate into the roaster tar, assuming that it does at all, the time course for such build up would suggest that the roaster was being used in a negligent and careless manner.  Michael Sivetz writes:
"Dark roasts leave oil and caramelized sugar deposits on the cylinder wall.  These deposits under prolonged exposure to such continual roasting conditions may cause partial or complete closure of the cylinder wall perforations.  Also, if these deposits carbonize, they are exceedingly difficult to remove.  Closed holes contribute to localized overheating of beans and the beginning of bean fires.  ... Cylinder wall tar buildup is due to neglect of roaster inspection and cleaning.  Roaster doors, ports, and ducting should be inspected weekly and cleaned as frequently as necessary.  Chaff, fines, broken beans, and oily residues contribute to smouldering and fire which may lead to a roaster shutdown (Sivetz and Desrosier, Coffee Technology, AVI Publishing, 1979, p 233.)

here is table #4 from the first reference:
(start of table - hard to line the numbers up in columns with their respective analytical methods)
   Table 4. The content of caffeine in coffees affected by different roasting degrees and determined by several different assays.
   Variety Roasting degree HPLC (%) Chloroform extraction (%) Micro-method (%) Lead-acetate method (%)
   Minas Green 0.66 ± 0.04a 0.56 ± 0.02 0.16 ± 0.00e 0.11 ± 0.01i
   Light 1.07 ± 0.03a 0.69 ± 0.02 0.25 ± 0.02e 0.13 ± 0.00i
   Medium 0.82 ± 0.03a 0.78 ± 0.00 0.24 ± 0.01e 0.13 ± 0.00i
   Dark 0.86 ± 0.01a 0.79 ± 0.05 0.23 ± 0.00e 0.15 ± 0.01i

   Cioccolatato Green 1.21 ± 0.11b 0.61 ± 0.03 0.08 ± 0.00f 0.17 ± 0.01i
   Light 2.24 ± 0.21b 0.64 ± 0.03 0.13 ± 0.00f 0.13 ± 0.00i
   Medium 1.59 ± 0.14b 0.68 ± 0.03 0.14 ± 0.01f 0.13 ± 0.00i
   Dark 1.53 ± 0.14b 0.73 ± 0.04 0.12 ± 0.01f 0.12 ± 0.01i

   Vietnam Green 1.92 ± 0.15c 1.07 ± 0.08 0.12 ± 0.00g 0.09 ± 0.00i
   Light 1.81 ± 0.14c 1.33 ± 0.10 0.16 ± 0.01g 0.11 ± 0.01i
   Medium 2.47 ± 0.23c 1.39 ± 0.10 0.19 ± 0.01g 0.11 ± 0.01i
   Dark 1.96 ± 0.16c 1.43 ± 0.12 0.16 ± 0.01g 0.11 ± 0.01i

   Cherry Green 2.07 ± 0.17d 1.07 ± 0.04 0.17 ± 0.01h 0.19 ± 0.01i
   Light 2.55 ± 0.21d 1.24 ± 0.09 0.28 ± 0.01h 0.11 ± 0.01i
   Medium 2.52 ± 0.19d 1.27 ± 0.10 0.27 ± 0.01h 0.13 ± 0.00i
   Dark 2.37 ± 0.13d 1.37 ± 0.12 0.30 ± 0.02h 0.15 ± 0.01i

   The same letters (a–i) denote the content of caffeine, which is not significantly (p > 0.05) affected by the roasting degree and coffee varieties.
(The above sentence is included at the base of the table - end of table inclusion)

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jpender
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Posted Tue Jul 23, 2013, 10:38am
Subject: Re: Roast and caffeine
 

Buckley, I have respect for Netphilosopher's knowledge, experience and contributions but I'm sure he would happily admit that he doesn't know everything. His extensive experiments with total soluble extraction have no direct bearing on caffeine content. In his own words: "There's just not enough information to conclude that roast level has any appreciable effect on caffeine content." So are you asking me to simply trust his opinion over those of others? I don't have a high standard for proof in this case but it's a little higher than that.

Before starting this thread I attempted to find an answer to the question by searching online resources. I had already attempted to look at the two journal articles you listed but they were protected by paywalls. My curiosity in this matter is not worth $35.95 per view. But prodded by your post I looked again and found that a website called yumpu.com serves up both of these papers -- hooray for the internet in circumventing copyright law!

Buckley Said:

You will find no consistent effect on caffeine levels by different roasting intensities in the following (papers)

Posted July 22, 2013 link

That's an odd conclusion since in the first paper on your list it is stated multiple times that there is a consistent effect:

"Our
results are in agreement with the ones obtained by Wanyika,
Gatebe, Gitu, Ngumba, and Maritim (2010), who also established
that dark roasted coffee has less caffeine than lighter roasts, be-
cause the roasting process reduces the bean's caffeine content."

"Based on the results of our study it can be observed that... intensified
roasting conditions decrease the caffeine content."

The second paper isn't as clear on the matter. They used two methods of extraction and two different coffee types. With arabica and what they called their "conventional" extraction method there was an increase in caffeine with increasing roast. It is interesting that they concluded that it is easier to extract caffeine from a darker roast since the matrix is more damaged.

The Wikipedia page on coffee roasting cites the following paper when claiming that darker roasted coffee has less caffeine. I would love to be able read it:

Verlengia F, Rigitano A, Nery JP, Tosello A. Variations of the caffeine content in coffee beverages. ASIC, 2nd Int Sci Colloq Green and Roasted Coffee Chem. 1965, 106-114.
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Netphilosopher
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Posted Tue Jul 23, 2013, 11:48am
Subject: ...
 

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Netphilosopher
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Posted Tue Jul 23, 2013, 11:52am
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Buckley
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Posted Tue Jul 23, 2013, 7:12pm
Subject: Re: Roast and caffeine
 

jpender Said:

That's an odd conclusion since in the first paper on your list it is stated multiple times that there is a consistent effect:

Posted July 23, 2013 link

Yes, however table four is their primary data concerning caffeine content of roasts and with some beans and assay methods it appears that the lowest concentrations can occasionally be in the medium or even the light roast.  Even when it is lowest in the dark roast the legend at the bottom states that no difference reached significant levels.  (I did not replicate their statistics.  Maybe I  should.)   If they choose to turn around and ignore the null hypothesis, and the editors let them get away with this, then this is just loose science.

jpender Said:

The second paper isn't as clear on the matter. They used two methods of extraction and two different coffee types. With arabica and what they called their "conventional" extraction method there was an increase in caffeine with increasing roast.

Posted July 23, 2013 link

I am in favor of saying that the variability of findings in general caffeine research is the only constant - more constant than the determination of caffeine levels.  I interpret this as the difference in caffeine levels among roast intensities is too insignificant to be consistently demonstrated by a multiplicity of assay techniques.  Perhaps we might refer to this as the Heisenbuckley uncertainty principle: the more one tries to measure caffeine levels in different roasts, the more uncertain one becomes.  The corollary is: the more one uses oneself as a biological assay instrument (i.e., the more coffee one drinks), the more one's hands start shaking.

jpender Said:

"Our
results are in agreement with the ones obtained by Wanyika,
Gatebe, Gitu, Ngumba, and Maritim (2010), who also established
that dark roasted coffee has less caffeine than lighter roasts, be-
cause the roasting process reduces the bean's caffeine content."

Posted July 23, 2013 link

Yes, and the authors continue to walk all over their own feet, for just after they write that, they write this:

"All four coffee varieties exhibited the highest caffeine content in the dark roasted coffees". (referring to the chloroform extraction method)(pg. 998)

jpender Said:

"Based on the results of our study it can be observed that... intensified
roasting conditions decrease the caffeine content."

Posted July 23, 2013 link

Part of that sentence is what was left out in the ellipsis: ..."the consumption of C. canephora (Cherry, Vietnam) can provide a higher caffeine intake, and that"...  The subject of that sentence is 'the consumption of C. canephora, and if one looks in table four at the percentage of caffeine in light, medium and dark roasts for the two varietals mentioned, one can see that they have contradicted their own data.  Just to give one example, the percent caffeine value assayed by HPLC for dark roasted Vietnam beans is higher than the light roasted value.  Other cells can also be found to show dark roast to be higher in caffeine in some instances, but, I admit, this is nitpicking.  The important finding in table four is that the standard deviations erase the differences in mean values between the different roast intensities, across the board.  There is no significant difference, in other words and in the authors' own words.  The authors comments to the contrary are not supported by their own data.

To answer the question "how much is caffeine reduced by roasting?", we have a choice of paradigms.  We can use the predictive model about what we know of caffeine's physical properties, similar to Netphilosopher's initial approach.  This does not take into account the possible reactivity of caffeine with other compounds present in the roast.  The second approach is to measure caffeine under different roast conditions, but what we are seeing are the variabilities introduced into the system by the different assay techniques interacting with an exceedingly complex mixture of compounds.  The question may be as perilous as the question, "What makes a good cup of coffee?" and the appropriate response to both may be just to free ourselves from having any attachment to a favorite unsupportable fact.

I cannot get Verlangia and Rigatano, either.  It is from a French society; that explains it.  Ooops, did I just faux pas again?

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jpender
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Posted Wed Jul 24, 2013, 11:48am
Subject: Re: Roast and caffeine
 

Buckley Said:

Yes, however table four is their primary data concerning caffeine content of roasts and with some beans and assay methods it appears that the lowest concentrations can occasionally be in the medium or even the light roast.  Even when it is lowest in the dark roast the legend at the bottom states that no difference reached significant levels.

Posted July 23, 2013 link

Perhaps you didn't read that the other assay methods were included in an attempt by the authors to find a less expensive means for those who cannot afford HPLC. The HPLC method was used as a reference for those inferior assays as it is "the most reliable and accurate method of analysis".

The HPLC results show a 20-30% drop in caffeine content for the arabica varieties. Of the two robusta varieties one decreased slightly and the other increased.


Buckley Said:

I am in favor of saying that the variability of findings in general caffeine research is the only constant - more constant than the determination of caffeine levels.  I interpret this as the difference in caffeine levels among roast intensities is too insignificant to be consistently demonstrated by a multiplicity of assay techniques.

Posted July 23, 2013 link

You could be right. But from my perspective that conclusion is premature. I've only seen these two papers. The one we're discussing now cites another work that apparently also found a reduction in caffeine. Are you assuming that it is flawed?
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jpender
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Posted Wed Jul 24, 2013, 12:02pm
Subject: Re: Roast and caffeine
 

Buckley Said:

Yes, and the authors continue to walk all over their own feet, for just after they write that, they write this:

"All four coffee varieties exhibited the highest caffeine content in the dark roasted coffees". (referring to the chloroform extraction method)(pg. 998)

Posted July 23, 2013 link

Again, the chloroform assay that they are discussing here was one of the inferior methods included by the authors in an attempt to find an affordable alternative to HPLC. If you look at the HPLC data it does support their previous statement.


Buckley Said:

Part of that sentence is what was left out in the ellipsis: ..."the consumption of C. canephora (Cherry, Vietnam) can provide a higher caffeine intake, and that"...  The subject of that sentence is 'the consumption of C. canephora, and if one looks in table four at the percentage of caffeine in light, medium and dark roasts for the two varietals mentioned, one can see that they have contradicted their own data.  Just to give one example, the percent caffeine value assayed by HPLC for dark roasted Vietnam beans is higher than the light roasted value.  Other cells can also be found to show dark roast to be higher in caffeine in some instances, but, I admit, this is nitpicking.

Posted July 23, 2013 link

I don't think they contradicted themselves. All of the roasts for each of the two canephora (aka robusta) varieties had a higher caffeine content (by HPLC) than all of the arabica roasts, with only one exception.


Buckley Said:

The important finding in table four is that the standard deviations erase the differences in mean values between the different roast intensities, across the board.  There is no significant difference, in other words and in the authors' own words.  The authors comments to the contrary are not supported by their own data.

Posted July 23, 2013 link

Can you explain how the differences are erased in these cases?

1.07 ± 0.03 - Minas Light
0.82 ± 0.03 - Minas Medium
0.86 ± 0.01 - Minas Dark

2.24 ± 0.21 - Cioccolatato Light
1.59 ± 0.14 - Cioccolatato Medium
1.53 ± 0.14 - Cioccolatato Dark


Buckley Said:

To answer the question "how much is caffeine reduced by roasting?", we have a choice of paradigms.  We can use the predictive model about what we know of caffeine's physical properties, similar to Netphilosopher's initial approach.  This does not take into account the possible reactivity of caffeine with other compounds present in the roast.  The second approach is to measure caffeine under different roast conditions, but what we are seeing are the variabilities introduced into the system by the different assay techniques interacting with an exceedingly complex mixture of compounds.

Posted July 23, 2013 link

I doubt that we could answer it by resorting to first principle. What is the sublimation rate of caffeine from roasting coffee beans? I personally think it is premature to give up on the literature after such a short excursion into it. Unfortunately we may have to for lack of access.


Buckley Said:

The question may be as perilous as the question, "What makes a good cup of coffee?" and the appropriate response to both may be just to free ourselves from having any attachment to a favorite unsupportable fact.

Posted July 23, 2013 link

Perilous?? I have no idea what you're talking about. I'm not attached to any answer, why would I be?
I'm just curious what the answer is.
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Buckley
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Posted Wed Jul 24, 2013, 7:12pm
Subject: Re: Roast and caffeine
 

jpender Said:

Can you explain how the differences are erased in these cases?

1.07 ± 0.03 - Minas Light
0.82 ± 0.03 - Minas Medium
0.86 ± 0.01 - Minas Dark

2.24 ± 0.21 - Cioccolatato Light
1.59 ± 0.14 - Cioccolatato Medium
1.53 ± 0.14 - Cioccolatato Dark

Posted July 24, 2013 link

No more than I can explain the adjacent cell, also under the HPLC column, where the lowest percentage of caffeine is in the light roast and the highest is in the medium roast with dark roast having an intermediate value for Vietnam beans.

BTW, what makes you think that sublimation accounts for any significant caffeine loss?  Caffeine is a classified toxin, absorbed by skin contact and inhalation.  If roasting drove out any appreciable amount of caffeine, one would think that at least one reported instance of job-related roastery toxicity might have been reported, perhaps not by inhalation, since it recrystallizes pretty quickly as it is removed from the heat, but by exposure to the roaster tars.

jpender Said:

Perilous?? I have no idea what you're talking about. I'm not attached to any answer, why would I be?
I'm just curious what the answer is.

Posted July 24, 2013 link

Roger that.

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