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 viticulture" written by Pierre Viala and Victor Vermorel and published in 1901–1910. Wine Grapes Wine Grapes - A complete guide to 1,368 vine varieties, including their origins and flavours is a reference book about varieties of wine grapes. The book covers all grape varieties that were known to produce commercial quantities of wine at the time of writing, which meant 1,368 of the known 10,000 varieties. It is written by British Masters of Wine Jancis Robinson and Julia Harding in collaboration with Swiss grape geneticist Dr. José Vouillamoz. "Wine Grapes" is not an update of Robinson's earlier book "Vines, Grapes