Crush Pad Operations
Sorting Wine Grapes
While most steps of grape processing aim to maintain the quality of the grapes, grape sorting provides an opportunity to actively increase the quality of the harvested grapes. Traditionally, wineries sorted grapes before they went into the destemmer-crusher. This was performed on conveyor belt tables and/or vibrating conveyor tables (sometimes with draining/small material slots) by personnel looking for material other than grapes (MOG) such as leaves, twigs, bugs, and also substandard fruit. Today, most wineries sort grapes after they have gone through the destemmer. Sorting post destemmer allows removal of stems and bits of rachis, which adds stem tannin that are quite different than skin tannins. It allows winemakers help dial in their fruit, helping reach a high of wine quality. Sorting post-destemmer allows underdeveloped berries, which can cause extreme astringency in some cases, to be picked out more efficiently because they are broken out of their clusters. This obviously helps with grape varieties that typically grow in tight clusters such as Riesling, Chardonnay, and Pinot Noir. It should be noted that the performance of sorting post-destemming will always be dependent on the condition of the grapes and the gentleness of the destemming process. Sorting performance is likely to be reduced if the grapes have been excessively damaged. For many winemakers sorting is the last line of defense between the vineyard and the winery.
Manual Grape Sorting Tables
Conveyor Belt Sorting Tables
sorting unit operation at this point in the process (i.e., prior to destemming and/or crushing). With conveyor belt systems, workers stand on either one or two sides of a moving conveyor belt, manually picking out the material to be removed. The main goal of this step is to remove MOG, along with unripe or moldy fruit that will affect the quality of the final wine.
Vibrating Sorting Tables
Vibrating tables are rather simplistic pieces of equipment constructed entirely of stainless steel (Figure 2.4). The table surface is mounted to the support frame with dampers to isolate vibration to the table only. The entire unit, top to bottom, is fully exposed and therefore is easy to wash down after use unlike conveyor tables. Vibrating tables have two distinct advantages. By
Automatic Grape Sorting Systems
Optical Sorting Systems
Optical sorters require the use of high-speed cameras and image-processing software for sorting the destemmed grapes according to color, size, and shape parameters (Figure 2.5). The settings that determine which material is being removed can easily be modified by reprogramming the software. To get a very accurate sorting, grape berries are spread out and conveyed to be delivered in a uniform way to the camera. Optical sorters usually have a belt with valves over the belt to remove undesirable material.
Vaucher-Beguet Mistral Sorting System
The Vaucher-Beguet Mistral system uses a two-stage vibrating screen and a subsequent air-jet to blow away remaining light materials. While on the vibrating table, juice that has accumulated as well as part of the small pieces of stems, petioles, and unfertilized berries are separated by means of a perforated plate embedded in the table.
Density Bath Sorting Systems
In addition to several mechanical separation systems, density bath sorters can be used to separate ripe and unripe grapes (Figure 2.6). The ripe grapes sink, while unripe grapes and MOG float in a grape juice/sugar solution of set density. Its advantage is that not only are contaminants removed from the grapes, but ripeness differentiation can also be applied. First the grapes are emptied into a hopper and move over a vibrating table with screens to remove juice and MOG. An incline conveyor gradually feeds the grapes into the destemmer.
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