Answer : Jeffrey B. Blumberg, PhD, director of Tufts HNRCA Antioxidants Research Laboratory, answers: “All plant food constituents are complicated but perhaps a bit more so for coffee, as how it is prepared can markedly affect its composition (and aroma and flavor).” Among the compounds in coffee thought to contribute to its apparent health benefits are chlorogenic acids. Says Blumberg, “While it is clear that instant coffee contains fewer chlorogenic acids than regular brewed coffee, there has been little or no study that directly addresses the question of health benefits of these differences. Moreover, the only studies that I have found in this area tested instant coffee specially fortified with chlorogenic acids but did not include a regular coffee control group.”
Instant coffee is made by concentrating and dehydrating liquid coffee (via spray drying, vacuum or freeze-drying), which affects the types and totals of biologically active ingredients in the coffee. Some instant coffees are fortified after this processing with chlorogenic acids, to improve the taste and aroma. These would presumably also have greater health benefits than non-fortified instant brands.
The answer is a bit clearer when it comes to terpenes-naturally occurring oils such as cafestol that have been linked with coffee-associated increases in serum cholesterol. “Terpenes are found principally in unfiltered coffee (e.g., French press),” says Blumberg, “with negligible amounts found in percolated, instant and drip-filtered coffees.”