Harvest (wine) of wine, winemakers would use the sugar and acid levels of the grape as a guide in determining ripeness. Early winemakers tasted the grapes to gauge ripeness. Modern winemakers use a refractometer to measure high sugar levels and °Brix or titration tests (using an indicator such as phenolphthalein) to determine the titratable acidity within the grape. In recent times there has been more of an emphasis on the "physiological" ripeness of the grape, usually in the form of tannins and other phenolics. Currently, tasting is the only way to measure tannin ripeness, which can take experience and skill to do
Wine Grapes and original work that is much more extensive in coverage, and also incorporates recent findings from ampelographic research, including DNA profiling of grape varieties. "Wine Grapes" include a catalog listing of 1,368 grape varieties from across the globe including 377 Italian, 204 French and 77 Portuguese wine grape varieties. Coverage includes a listing of synonyms as well as the genetic relationship between varieties derived from DNA analysis. According to Jancis Robinson and José Vouillamoz, "Wine Grapes" includes details about almost 300 previously unpublished relationship between different grape varieties including the extensive family tree of the Pinot grape that includes a