<P> The majority of the world's wine producing regions lie between the temperate latitudes of 30 ° and 50 ° in both hemispheres with regions lying closer to the equator typically harvesting earlier due to their warmer climates . In the Northern Hemisphere, vineyards in Cyprus begin harvesting as early as July . In California some sparkling wine grapes are harvested in late July to early August at a slightly unripe point to help maintain acidity in the wine . The majority of Northern Hemisphere harvesting occurs in late August to early October with some late harvest wine grapes being harvested throughout the autumn . In Germany, Austria, the United States and Canada, ice wine grapes can be harvested as late as January . In the Southern Hemisphere harvest can begin as early as January 1 in some of the warmer climate sites in New South Wales, Australia . The majority of Southern Hemisphere harvesting occurs between the months of February and April with some cool climate sites like Central Otago, New Zealand picking late harvest wine grapes in June . </P> <P> Recent climate changes (particularly global warming) have shifted the harvest season in some countries; future weather patterns may exceed a climatic threshold in some vineyards where it will be more difficult to maintain the current wine quality, however they could also push some regions into more optimal climatic regimes for the production of equilibred grapes . </P> <P> Throughout the history 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 hi sugar levels and ° Brix or titration tests (using an indicator such as phenolphthalein) to determine the titratable acidity within the grape . </P> <P> 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 accurately . Viticulturalists have not yet fully explained the complex processes that go into the ripening of tannins but most believe it begins with the polymerization of small astringent tannins into larger molecules which are perceived by the taste buds as being softer . </P>

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