Distillers grains and syrup are coproducts from fuel ethanol dry grind processing. Ethanol manufacturing is dramatically increasing in the United States, primarily in Midwestern states, and thus the availability of these feed products is also growing. Confusion currently exists in industrial nomenclature regarding "solubles" in these streams because no standards are in place. In our study, dissolved materials were considered soluble matter. We developed a methodology to determine the dry basis soluble content in condensed distillers solubles (CDS) and distillers dried grains with solubles (DDGS). A mass balance analytical approach was initially used, but results were not in good agreement with experimental data. This method was thus deemed a poor predictor of final soluble content. This led to the development of a new methodology for determining, as well as predicting, soluble content for various coproduct streams, which produced results with R 2 > 0.96. This approach is applicable for all dry grind ethanol coproduct streams and is useful for value-added product development research.