Harvesting the grapes
The harvesting of wine grapes (vintage) is one of the most crucial steps in the process of winemaking.The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannins levels with winemakers basing their decision to pick based on the style of wine they wish to produce. The weather can also shape the timetable of harvesting with the threat of heat, rain, hail, and frost which can damage the grapes and bring about various vine disease. In addition to determining the time of the harvest, winemakers and vineyard owners must also determine whether to utilize hand pickers or mechanical harvesters.The question of using mechanical harvesting versus traditional hand picking is a source of contention in the wine industry. Mechanical harvesting of grapes has been one of the major changes in many vineyards in the last third of a century. First introduced commercially in the 1960s, it has been adopted in different wine regions for various economic, labor and winemaking reasons. In Australia, the reduced work force in the wine industry has made the use of mechanized labor almost a necessity.
A mechanical vine harvester works by beating the vine with rubber sticks to get the vine to drop its fruit onto a conveyor belt that brings the fruit to a holding bin. As technology improves mechanical harvesters have become more sophisticated in distinguishing grape clusters from mud, leaves and other particles.
Throughout the history of wine, winemakers would use the sugar and acid levels of the grape as a guide in determining ripeness. Early winemakers would taste the grape to get this gauge but more modern winemaking would use a refractometer to get a measure of the sugar levels in the form Brix and a titration test to determine the titrable acid 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.