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Thread: Coffee Snob + Biochemistry Nerd = Coffee volatile profile

  1. #1
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    Coffee Snob + Biochemistry Nerd = Coffee volatile profile

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hello Fellow Snobs,

    I thought that I would share something that I thought would interest you. I'm a biochemist that specialises in studying metabolism by using mass spectrometry to detect and identify metabolites. I'm also a home roaster that supplies roasted beans for my lab groups morning coffee. My colleague decided to use an espresso shot from one of my blends as a test sample for the development of a new sample preparation method that we are setting up (solid phase micro extraction - for anyone that is interested). The sample was analysed by gas chromatography - mass spectrometry which allows us to detect the volatile chemical compounds that are present in the espresso shot. A lot of these chemical compounds will be a product of the metabolism of the coffee plant when it was growing, as well as products of the coffee roasting process. I have attached two pictures that show some of the results.

    The second picture is a GC-MS chromatogram that shows all the compounds detected, where each peak represents a chemical compound (or possibly more if there is coelution). The first picture is the mass spectral fingerprint of the peak at 14.3 minutes, which corresponds to caffeine - we see the spectrum from the sample up the top, while the spectrum below is the library match that identifies it as caffeine.

    The blend was a 2:2:1 ratio of Tanzania KVCG:India Elephant Hills AA:India Elephant Hills Monsoon, taken to just on second crack.

    We plan on doing a few more of these experiments as we develop the method, which I'll hopefully get a chance to post. Anyway I hope this interests some of you.

    Cheers, DaveIMG_2373.jpgIMG_2374.JPG
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    Senior Member speleomike's Avatar
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    Hi Dave

    Thanks for that. There are so many compounds in the coffee that it would be a good training ground for students to learn analytical techniques.

    Now we already have snobs that want to know everything that's happening during an extraction in real time ... some have thermocouples inserted into the group head, some have pressure gauges, you could insert the SPME fibre into the group head and profile the compounds in real time :-)

    Mike
    Last edited by speleomike; 15th February 2015 at 04:27 PM. Reason: Fix grammar

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    Senior Member speleomike's Avatar
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    Hi again

    So to understand what you do. You place the SPME fibre into the espresso from the shot by just dipping it into the cup? So it's in crema or has the crema dissipated and its just straight black? Then how do you desorb the analytes from the fibre to get them into the GC-MS input stream, just heating the fibre or laser/plasma?

    Mike

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    Hi Mike,

    Just the interest I was hoping for. Another scientist I take it? The fibre is dipped into the straight black, then inserted into the hot inlet of the GC, which is held at 250C. The volatile compounds will thermally desorb and will go into the gas phase, and then get swept onto the column when the run is started. Helium is used as a carrier gas.
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    Senior Member speleomike's Avatar
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    Hi Dave

    Thanks, now I can understand and visualise the procedure better. Yes, ex-physicist here :-)
    The straight black will be essentially aqueous, you'd need a different extracting phase I presume for the crema which is much higher in oils. Will be interesting to see after many tests on different beans if you can identify that bean as being present in a blend by analyzing the coffee. And sometimes it isn't a particular fraction but the ratios of fractions that are unique.

    Will be nice research for students.
    "Ok students, back to work pouring coffee shots for your supervisor" :-)

    Mike

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    Yeah, Mike that's absolutely correct. As it happens I've roasted two of the beans from the blend as SOs, and wanted to do exactly as you suggested to see if we could dissect out the contributions of the individual origins. Includes though this is a bit of fun add part of the analytical method development. Our research is more biomedical, so will have to focus on that, but will have fun with it while we can. It certainly makes fora good final slide to leave an audience with when I give talks or lectures.
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    Behmor Brazen - $249 - Free Freight
    Thought I'd post this link to a great article about coffee volatile compounds. It was great that we could see quite a few of them in the profile that we had collected.
    www.compoundchem.com/2015/02/17/coffee-aroma



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