caffeine -- how do they test?

[Andy]

while we all read about the caffeine content in drinks (obviously coffee included) can any one tell me how they test the quantity? I assume makers of caffeine / sugar drinks know the contant because they add it in.

It seems that most coffee caffeine content quotes can be sourced to a paper from the 70s (from a time and country that considered simmering for hours good coffee).

I would love to have a pile of espresso shots tested from different roast depths and origins to get an idea of actual caffeine content.

So... where do we book a day of caffeine tests?

[askthecoffeeguy]

Re: caffeine -- how do they test?

Try your local doctor

[Andy]

Re: caffeine -- how do they test?

seriously?

[Dennis]

Re: caffeine -- how do they test?

csiro?

[blweaver]

Re: caffeine -- how do they test?

Hmmm....sounds like a food lab coming along....All chemicals should be easily available.....but you never know these days buying them could put you on the terrorists watchlist!!

Here is a simple method.....

http://www.newton.dep.anl.gov/askasci/chem00/chem00291.htm

[mwatt]

Re: caffeine -- how do they test?

http://www3.interscience.wiley.com/cgi-bin/fulltext/68000104/PDFSTART

Sponsored by illy.

Scientific description of coffee:

"Espresso coffee is served in a small, heavy china cup
with a capacity of 30±50ml, half-full with a dark brew
topped by a thick, clean, light reddish-brown foam of
tiny bubbles. The liquid part of the espresso is a very
complex matrix. It is in fact a concentrated solution of
salts, acids, sugars, caffeine and many other complex
substances, forming the matrix wherein three dispersed
phases coexist (emulsion, suspension and gas
bubbles)".

The bottom line:



Sorry about the lack of cropping employed there. But basically 40mg caffeine per espresso shot.

[Andy]

Re: caffeine -- how do they test?

Cool link NakedBean, ta.
It looks fairly straight forward and I agree with avoiding benzene (and would add to be cafeful with Lead Acetate!)

Thanks Michelle, yes some of the figures quoted are fairly current but without knowing the roast depth and origin of the beans (just a generic variety or Arabica / Robusta is often used) I cannot be sure we are real comparing apples.

[mwatt]

Re: caffeine -- how do they test?

Hmm, but as I understand it, the paper was also about a method theyve developed to measure caffeine:

"a potentio-metric enzyme sensor can be used successfully for the direct detection of caffeine in coffee beverage samples. The system described here does not require any sophisticated equipment, being based on a pH meter with a glass membrane electrode".

So, if that means more to someone else than it does to me, then theyd also be able to analyse and compare espresso beverages made of different origins/ roast profiles.

My husband was also mumbling something about gas chromatography when I was talking to him about this...

[Sullo]

Re: caffeine -- how do they test?

this may be a bit off the wall but what about contacting choice magazine or today tonight and ask if they can recommend a lab they use for food testing, might be a way to also see what methods are used? the csiro would most probably have the facilities to test or a local university but getting the beans to the lab and at what cost would probably come into the equation.
worth a shot isnt it? (no pun intended)

[Andy]

Re: caffeine -- how do they test?

Whoops, sorry Michelle, I didnt see the link in the top of your post (eyes just missed it!) and I was refering to the image.

potentio-metric enzyme sensor eh? I had a bit of scrounge in the shed and dont seem to have one (or a gas chromatograph)

Normally, high-performance liquid chromatography separation4±8 and UV spectrophotometric detection 9,10 methods are applied to both regular and decaffeinated green and roasted coffees for caffeine content determinations. Also, other methods such as capillary electrophoresis,11±14 thin layer chromatography
15 and gas chromatography,16 are used for separation of caffeine in the analysis of mixtures, combined with several other detection methods such as mass spectroscopy16 and FTIR spectrophotometric measurements.17±19 However, very costly instrumentation, highly skilled technicians and complicated and time-consuming procedures are required for such methods.


Its a great article (belated thanks) and goes some way to explain why everyone quotes and re-quotes the same old figures... its darn hard to get a good reading easily.

Sullo, I worked for the local Uni for 8+ years and that might be worth a try. I currently do some work for a business that has a "lab" that test olive oil so I might brush-up on my spanish and have a chat to thier head scientist.

I did see some reference to a canadian doctor who was developing a simple test but I expect his is a "yes/no" type test.

[mylesau]

Re: caffeine -- how do they test?

Hi Andy,

Not sure how useful this will be, youve probably already covered the ground...  If you do a Google search on "extraction of caffeine from tea" or "isolation of caffeine from tea", you should come across a heap of laboratory prac. procedures for extracting caffeine from tea which should be easily modified for coffee.  Most of the chemicals are relatively safe and should be obtainable, though you will most likely require a fume cupboard, or a very well ventilated open area.  I think the first step of obtaining natural caffeine should not be too hard, purifying it (via crystallisation) might be a bit trickier.  But if you are just after a comparative indicator it should not be too difficult...

I actually did something similar in my younger days, we extracted caffeine from both Tea and Coffee to see which contained the most.  Interestingly, if I recall correctly, by weight (not cup) Tea actually had it over Coffee.  I cant recall what type of coffee we used (i.e. instant or ground).

Ive forgotten way too much about organic and analytical chemistry, so cant offer too much more, just wish Id kept my old prac. book.........

Depending on what you want to do, it might be easier to send of samples to a lab for processing ~ High Pressure Liquid Chromatography certainly looks like the simplest method to use.

[blweaver]

Re: caffeine -- how do they test?

You dont really state what degree of accuracy youre looking for but considering Chromo and AAS are out of the question for cost etc, so to would be any chemistry based analytical approach.
2 quick and dirty things spring to mind that may get you to close enough...

1. A few standard solutions made from distilled water and pure caffeine (you must be able to buy it somewhere) and a pH reading of those. Then compare or extrapolate from your sample to those standard solutions.......

2. A quick and dirty "simply boil the hell" out of your weighed samples and then wash and dry and weigh the samples again.......but that will take out all soluble compounds and I dont have any idea what those would be as a % of the caffeine. Of course there would always be some residual caffeine left just as per the water process for de-caff.

3. Another could simply be extract a normal espresso shot and drop the caffeine out by precipitation.....

But Im only guessing but it might be some food for thought.....I havent done any chemistry for 20 odd years and all of that was for mineral exploration.

[blweaver]

Re: caffeine -- how do they test?

Some more digging,,,,

Does dark roast coffee have less caffeine than light roast?
http://coffeefaq.com/site/node/15

How do I measure caffeine content at home?
Submitted by Daniel on Mon, 2006-01-16 01:17.
To the best of my knowledge this can not be accomplished without sophisticated equipment. The Department of Energys web page briefly explains what is involved.

http://www.newton.dep.anl.gov/askasci/chem00/chem00291.htm

(I think that is the original URL I posted previously)

When isolated and purified, caffeine is a white, crystalline powder. It is composed of long hexagonal prisms. It ultimately melts at 458.2 °F (236.8°C), losing water at 176°F (80°C) and subliming at 352.4°F (178°C). It is odorless and has a bitter taste. It is slightly soluble in water and alcohol and is typically heated when incorporated into beverages. Aqueous solutions of caffeine have a neutral pH.

My pH quick and dirty obviously isnt a goer as it should be neutral pH.....doh!!!!

I think this is the answer....but it doesnt describe getting the caffeine out of the solution....

http://antoine.frostburg.edu/chem/senese/101/matter/faq/decaffeinating-coffee.shtml

[blweaver]

Re: caffeine -- how do they test?

Nothing dangerous about this one and it could be what you require.

http://www.seriaz.org/downloads/4-caffiene.pdf

However weighing to 0.001g is going to cost you!!

[mylesau]

Re: caffeine -- how do they test?

...out of the question for cost etc, so to would be any chemistry based analytical approach.

Not sure why youd suggest that?  The chemicals required for an analytical approach are quite low cost ~ Id guess at considerably less then $100, which would go toward a reasonable number of samples.  Only other requirement is a bit of glassware which should be readily available with alternatives likely to be substituted.