The Caffeine FAQ

This is an excerpt of a longer FAQ including more coffee-related information which can be found here. The primary author of this documemt is Alex López-Ortiz. alopez-o@daisy.uwaterloo.ca . For a list of contributors, see end of page.

Since the FAQ doesn't cover some issues related to home roasting, I have been so bold as to add some discussion from the HomeRoast List on this topic at the bottom of the page.


  • The Chemistry of Caffeine and related products
  • Caffeine and your Health
  • Authors of this FAQ
  • The Chemistry of Caffeine and related products

    Caffeine and your Health

    Important: This information was excerpted from several sources, no claims are made to its accuracy. The FAQ mantainer is not a medical doctor and cannot vouch for the accuracy of this information.

    Author and Contributors


    This is an excerpt of a longer FAQ including more coffee related information which can be found here. Copyright (C) 1994, Alex López-Ortiz. alopez-o@daisy.uwaterloo.ca (this email seems to be defunct? -Tom 6/03)


    Caffeine and Home Roasting

    Since the FAQ doesn't cover some issues related to home roasting, I have been so bold as to add some discussion from the HomeRoast List on this topic.

    Tom's email:

    Q: Could the roast level be affecting the amount of caffeine?
    A: Everything I have read would indicate "no". Caffeine is very chemically stable, amazingly so since everything else in coffee changes so much in roasting.
    Q: Or could it be the different types of extraction - espresso vs. drip?
    A: I think it makes more sense to simply look at the amount of coffee used to brew, by whatever method. Basically, more ground coffee used means more caffeine. Caffeine washes easily out of the coffee into the cup. Only by some serious underextraction would you get less caffeine. BTW: if you measure coffee by weight, you would get more caffeine with a darker roast if my notion that there is negligible loss of caffeine in roasting since you do lose 18-23% of the weight of moisture and other compounds...

    Dave's comment:

    I have no experimental data, BUT I suspect that roast level does affect the amount of caffeine remaining in the bean. My guess is that darker roasted beans have less caffeine than lighter roasts.
    Way back in Organic Chemistry lab (about 45 years ago) one of the experiments we did involved purifying caffeine by sublimation. Caffeine passed from the solid state to a gas, then condensed again to give really pretty crystals, leaving impurities behind. As I recall, it didn't take lots of heat for sublimation to occur.
    So I suspect that some caffeine is vaporized during roasting, and longer/darker roasting would likely lead to a greater loss of caffeine.
    Dave
    Westerville, OH

    Deward's Comments:

    Tom:
    Regarding roast level and caffeine . . .
    You are correct about caffeine being quite stable (in comparison to other
    coffee bean components), but it has an appreciable vapor pressure at final
    roasting temperatures, so a significant amount can outgas along with CO2 and
    volatile oils (water will be mostly already gone late in the roast when this
    can occur). In a drum roaster with limited airflow an equilibrium will
    establish, with volatilized caffeine re-condensing on the beans for little
    net loss, but in an air roaster (or a drum with significant airflow)
    vaporized caffeine will be carried out of the roaster (and there have been
    many comments here about home roasters getting a "caffeine jangle" from the
    exhaust).
    There is also variance with extraction method. Although caffeine is very
    soluble in water an espresso extraction leaves perhaps 20% of the extracting
    water behind in the puck, and with it a similar percentage of the caffeine.
    In other brewing methods the retained water is a smaller percentage of the
    total extract, which implies less residual caffeine in the grounds.
    Both mechanisms above (assuming the typically darker roast for espresso use)
    would contribute to the commonly presented measurements which show less
    caffeine in espresso than in press, vac or drip extractions (assuming an
    equal weight of ground coffee is used per dose (serving).
    All else being equal, other variables may apply, and YMMV, of course . . .
    < g>
    Deward

    Tom's response:

    I am not sure if adequate temp.s are reached in roasting - here's a reference:

    In an article in the Jan/Feb 2005 Roast Magazine Jim Fadded wrote;
    " Popular lore has always been that the darker the roast level, the lower the
    caffeine content. This is not really the case, as caffeine changes very
    little during the roasting process. Caffeine has a very stable crystalline
    structure with a boiling point above 600 degrees Fahrenheit, far above
    roasting temperatures, which rarely exceed 470 degrees Fahrenheit. This
    means there is very little change to the caffeine during the roasting
    process." (Fadden)

    (after this post, we were forwarded contrasting information that caffeine does not have a boiling point and that it actually subliminates at 352 degrees F. You can view this information on page 7 of this document). This is an interesting point because of the new fad of green coffee used in beverages for antioxident value. This would mean there is more caffeine content if the coffee is unroasted.

    Q: Does fresh Home Roasted coffee have more caffeine - I am feeling buzzed after changing over to 100% home roasted coffee...

    A: There's no reason that it would. If you drank cheap commercial coffee (R/G -Roasted / Ground brands, like Maxwell House etc ) then you would usually be getting some Robusta in the blend, which actually means higher caffeine contents (Robusta is in the range of 2.2% and most Arabica is in the 1.1% to 1.3% caffeine range). Then again, as a matter of taste cheap coffees tend to be portioned more strictly (very strictly in the case of office coffee portion packs), or people simply brew weaker as a matter of taste. Less ground coffee used to make the cup means less caffeine. It might be that people brew home roasted coffee stronger, or simply enjoy more coffee because it smells and tastes good!

    Q: Is there more caffeine in espresso than drip, or French Press?

    A: Focus not on the brew method but on the amount of ground coffee used to make what you drink. Caffeine is easily percolated out of the ground coffee into the cup, so the amount of caffeine tends to be a direct result of how much coffee is used to prepare the beverage. Some people use little coffee, make weak dribbly espresso and get little caffeine. So a certain brew method isn't necessarily stronger than another.

    -Tom


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