A Technical Guide for Wine Producers

RECENT ARTICLES   |   WYNBOER HOME WHAT'S UP IN THE VINEYARD AND CELLAR Mechanical harvesting of grapes by Charl Theron Mechanical harvesters have become a common sight in South Africa. Producers have been obliged to replace the traditional manual harvesting of grapes with this mechanical alternative. Indications are that the trend will continue, spurred by ongoing technical development of harvesters. Mechanical harvesters were initially used in the 1960s in the Central Valley of California to harvest cheap grapes for vin ordinaires; by the following decade it had become popular in Europe, where many vineyards are privately owned and insufficient labour necessitated alternative harvesting methods. Since then several new generations of harvesters have been developed. Currently there are two types which beat and shake the vine, either by means of staves beating the foliage, or the impulse harvester which beats the trunk and cordon. Both aim to detach the berries. The berries are then collected on a conveyor, which moves past a blower that removes the leaves, whereafter they are dumped into a bin. Mechanical harvesters are able to work against slopes and adjustments may be made without stopping. Three basic adjustments may be effected, namely the width between the two sets of staves (“pitch”), the extent of the beating action (“amplitude”) and the speed of the beating action (“frequency”). Different combinations of these three factors may be used for various vineyards. The success of mechanical harvesting is ascribed 35 - 40% to the harvester, 30% to the operator and 30% to the vineyard. If the canopy is not suited to mechanical harvesting, the process will not be successful. In California mechanical harvesting of grapes may be two to five times cheaper than manual harvesting. Mechanically harvested grapes may also be delivered to the cellar at lower temperatures. As may be expected, there are few whole berries when grapes are mechanically harvested, but if the grape mass can be processed within an hour of being harvested, oxygen exposure is minimal. If this period is extended to ten hours, however, one may expect much greater oxidative reactions. New generation harvesters offer several new advantages: Automatic sorting takes place on the harvesters to present whole berries without any material other than grapes (MOG: Material Other than Grapes). The sorting of different colour berries. The sorting of the grapes according to the condition and ripeness of the grapes. The success of mechanical harvesting is largely influenced by the maintenance of the harvester and the training of the operator. A comprehensive service is essential before the harvest, likewise there should be daily services. These include, inter alia, an intensive cleaning action after each shift. Although basic training is invaluable, operators will learn from experience how to obtain the best results from various vineyard blocks. The current view is that mechanical harvesting of grapes is suitable for average wines, but that premium wines should still be made from manually harvested grapes. This notion might change in view of the ongoing development of harvesting technology. A more accurate assertion might be that the decision to harvest mechanically is determined by various factors such as the cultivar, viticultural practices and specific vinification requirements. Reference Cutler, Lance. 2008. Industry Roundtable: Winemaking with Mechanically Harvested Grapes. Wine Business Monthly 15(11): 20 - 26.

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