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Caffeine Content in Coffee Beverages
There is a lot of talk, but not much fact, about caffeine content in coffee. One of the difficulties is that there is a huge variability on caffeine content in green beans in general. What we know is that altitude is not a factor.

A study presented at ASIC says the most significant factors for caffeine content for a given coffee lot is (in order of importance) grind, preparation method, degree of roast.

Their tests revealed that coffee roasted and ground to typical value for various preparation methods had these caffeine percent content when 70g of the same coffee (various roasts and grinds) in a liter of water:

Sack (medium roast, coarse grind) = 0.045 (and probably Drip)
Percolator (medium roast, coarse grind) = 0.065 (and probably Press)
Espresso (dark roast, fine grind) = 0.060

In all tests, 70g of the same Arabica coffee was used for each liter of water.

For all preparation methods, with an given combination of grind and roast, the percolator always extracted more caffeine and the espresso machine the least.

What this says, if my math is correct is that each gram of coffee will yield this much caffeine for the the same preparation methods, roasts, and grind:

Sack (Drip) = 6.43mg caffeine / gram coffee
Percolator (Press Pot) = 9.29mg caffeine / gram coffee
Espresso = 8.57mg caffeine / gram coffee

So, if you make a double-shot of espresso with 16g coffee, expect 137mg of caffeine.

If you use 35 grams to make a press pot of coffee and pour that into two, big mugs, they will have 163mg of caffeine in each.
Edited by Dan on 09/10/2007 6:03 PM
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