Coffee is one of the most commonly drunk beverages in the world, and we Americans have a particular enthusiasm for it. Because of its abundant presence in modern culture, scientists have long speculated about the health benefits of coffee, especially those benefits related to its antioxidant content. With the advent of new technology and research techniques, we are getting closer to determining how much protection coffee offers your body from harmful free radicals. The methods used to hone in on an elusive goal like this are vast. They range from experiments done purely to identify how many antioxidants are present in a cup of coffee, to how many of these antioxidants actually get absorbed into the blood stream. Still another way to evaluate coffee’s benefits is to examine large numbers of coffee drinkers and look for an inverse relationship between drinking coffee and a the occurrence of a disease.
To examine the antioxidant content of coffee, scientists measure the radical scavenging activity of coffee. This involves tests that measures coffee’s ability to reduce radicals in vitro, or outside the body in an environment that doesn’t resemble the body. The first study looked at the antioxidant activity of two different types of coffees roasted at four temperatures. The coffees used were robusta (from sub-Saharan Africa) and arabica (from Northern Africa and the Middle East), and the four roasting temperatures were zero, 170, 180, and 190 degrees Celsius. After conducting tests to measure the radical scavenging activity of coffees across all variables, researchers found that unroasted (green) arabica coffees had almost half the antioxidants of green robusta coffees. Furthermore, it was found that roasting nullified this difference in antioxidants. An increase in roasting temperature was found to decrease the antioxidant content of the coffee regardless of origin (7).
Still another study was done in relation to the types of antioxidants present before and after roasting different coffees. Researchers found that despite the decrease of total antioxidants with roasting, there was an increase in the phenolic antioxidants present after roasting. These phenolic antioxidants that emerge with roasting more closely resemble antioxidants that are known to be biologically active. Roasting only effectively brings out phenolic antioxidants when roast time is between twenty and sixty minutes. After the sixty minute mark, coffee’s antioxidants begin to degrade further and lose radical scavenging ability (8).
The reaction thought to be responsible for the observed increase in antioxidants with roasting is the Maillard Reaction. This is a complex, multi-step reaction occurring between sugars and amino acids present in the coffee bean. The reaction’s products and rate are dependent on a plethora of factors, namely temperature and Ph. Although the mediary steps are complex, all results of the reaction are either aldimes, ketimes, or malanoidins. The melanoidins, brown pigments that arise with roasting, are thought to exhibit antioxidant activity. Researchers explain that this is why darker roasts, or coffees roasted longer, have the highest phenolic antioxidant content. Although details of the Maillard Reaction are still being mapped, it is clear that a correlation exists between Maillard Reaction products and antioxidant activity (4). [pic]
(Table illustrating complexities of Maillard Reaction, Martins, Sara I.F.S.)
It is important to consider that simply mapping the antioxidant content of coffee does little to tell us how it will behave when ingested. Further investigation needs to be done to illustrate what antioxidants present in coffee are active in the human body. One way to isolate potential biologically active antioxidants is to simulate the body’s environment in a laboratory setting, and see what antioxidants work in that setting. One such in vitro test done at the...