5 Jul 2008

Coffee - The Science - (Part 2 of 2)

- 22 Aug 2003

By Stuart Brown

Page 1 of 5

Note - If in any doubt Consult your Doctor! This information is NOT a replacement for his/her advice. Coffee - The Science (Part 2 of 2) (Cick Here to read part 1)

To start with lets take a look at what is actually in coffee. The chemical constituents of coffee that we are interested in are those compounds in roasted coffee beans that are soluble in boiling water (because that's the stuff you are actually drinking). The list of chemical constituents is a long one, and you can see an attempt at a detailed composition list of arabica coffee here courtesy of Dr Dukes Phytochemical and Ethnobotanical Database (sounds like something you would hear in a cowboy film - 'Roll Up ! Roll Up! Get yourself some 'Dr Duke's Phytochemical and Ethnobotanical Elixir!'). However, in practice the composition of coffee has proved very hard to pin down accurately due to the large number of different compounds contained in coffee (often estimated at over 2000); and the different ways that scientists classify them. One attempt by a scientist called M Clifford, which is widely accepted is as follows:

A summary of compositional data (in %) for green and roasted arabica and robusta coffee beans and instant coffee powder
Component	Arabica	Robusta	Instant

	Green	Roasted	Green	Roasted
Minerals	3 - 4.2	3.5 - 4.5	4 - 4.5	4.6 - 5	9 - 10
Caffeine	0.9 - 1.2	~1	1.6 - 2.4	~2	4.5 - 5.1
Trigonelline	1 - 1.2	0.5 - 1	0.6 - 1.75	0.3 - 0.6	-
Lipids	12 - 18	14.5 - 20	9 - 13	11 - 16	1.5 - 1.6
Total Chlorogenic Acids	5.5 - 8	1.2 - 2.3	7 - 10	3.9 - 4.6	5.2 - 7.4
Aliphatic Acids	1.5 - 2	1 - 1.5	1.5 - 2	1 - 1.5	-
Oligosaccharides	6 - 8	0 - 3.5	5 - 7	0 - 3.5	0.7 - 5.2
Total polysaccharides	50 - 55	24 - 39	37 - 47	-	~ 6.5
Amino Acids	2	0	2	0	0
Proteins	11 - 13	13 - 15	11 - 13	13 - 15	16 - 21
Hunic Acids		16 - 17		16 - 17	15

Now this is one scary looking chart! And the fact that none of the columns add up to 100% (or anywhere close) should give you a clue as to how sure scientists are about what makes up coffee. Unfortunately then the real mysteries of what makes coffee tick are frankly not properly understood. This is why of all the above ingredients the one that we are really concerned about here is caffeine. This is because the physiological effects of this on people has undergone considerable research. To a lesser extent also chlorogenic acids which are being investigated for possible antioxidant benefits and there is ongoing research into the other constituents (which might make up 98% for example of roasted arabica beans) in the numerous 'coffee institutes' set up by different coffee producers. But for a product worth $70 billion to the world economy there is really surprisingly little known about how these other compounds interact in coffee; and so it is generally caffeine that gets all the attention.