MadSci Network: Chemistry

Re: How to read how much caffiene is ina cup of coffee?

Date: Mon Dec 13 14:58:58 1999
Posted By: Jill Irvin, Staff, Food and Nutrition, Ohio State University
Area of science: Chemistry
ID: 941646930.Ch

First, Brad, I apologize for how long it has taken me to reply to your question. 
I didn't receive it until recently so have been as prompt as possible.

The roasted coffee bean is 1.2 % caffeine (by weight) but the amount of caffiene 
in a cup of coffee is dependent on the method of brewing. I made a table below 
of the different brewing methods and the average amount of caffeine in a 5 oz 

Percolated                   just over 100 milligrams (mg)
Nonautomatic drip            142 mg
Automatic drip               151 mg
Instant, freeze dried         66 mg

Therefore, I don't think you will ever find anything on a package of coffee 
about the caffeine amount. You would need to look it up in some kind of 
reference or text book. I found this information in Food Science, 2nd edition,  
Helen Charley, 1982. Since this book was published, espresso has gotten more 
popular. I don't know how much caffeine would be in a cup of espresso but I 
would think that it would be higher than the amounts above.

As I reread your question, I wonder if you are asking me how do you determine 
the caffeine - what kind of tests do you run? I don't know the specific 
procedure to analyze for caffeine. Chemically, caffeine is 
1,3,7-trimethylxanthine or methyl theobromine.

I hope I have answered your question. Again, I apologize for taking so long.

Jill Irvin, RD
Ohio State University

Admin note from Kieran: You can also try the following link for more information 
about caffeine, concentration in different beverages, and health effects:  

Caffeine FAQs

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