|MadSci Network: Chemistry|
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 cup: 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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