|MadSci Network: Biochemistry|
You an access the "nutrient" composition of coffee from the National Nutrient Data Lab's web site at http://www.nal.usda.gov/fnic/foodcomp/Data/index.html. This will give you the composition in terms of nutrients, but natural foods have many, many components that will not be listed as nutrients. Evaporation will not change most chemical components but could result in the loss of volatile components. Mold growth in the liquid coffee and oxidation of components in the dry powder could result in chemical differences between wet and dry coffee. You may argue that changes due to evaporation are negligible, or that loss of volatile components makes the dry product chemically different. Aren't arguments fun!
University of Iowa
Clinical Research Center
Try the links in the MadSci Library for more information on Biochemistry.