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
Straw wine Czech wine law, is classified as a Predicate wine (Czech: "Jakostní víno s přívlastkem"). Czech regulations require the harvested grapes to come from a single wine sub-region, the grapes must be dried for at least three months either on straw or reed mats or hung in a well-ventilated space, and the must weight is required to reach at least 27° NM on the Normalizovaný moštomer scale. Straw wine in the Czech Republic is typically made from white grapes that are well-ripened and undamaged. Vin de Paille is the French for 'straw wine', made only in the ripest vintages. Perhaps the