What is MOG (Material Other than Grapes), nongrape material or foreign matter
MOG comprises leaves, stems and other foreign matter in harvested grapes. This foreign matter may also include insects, shoots, weed residue, stems, parts of trellis systems, stones, irrigation systems, pressing equipment, etc. Apart from the fact that the material may damage mechanical
harvesters and pressing/cellar equipment, it may also contribute to odours and tastes that are mostly undesirable in the end product, i.e.
wine. It is therefore necessary to take the utmost care that the abovementioned objects do not end up in the press bin. If any of said material
does end up among the grapes during the crushing process, it will have to be removed so that it does not affect the wine quality or damage the machines It is very important for the harvesting teams to understand that the MOG may impact negatively on wine quality, as these are the teams who have to ensure that the grape bunches which end up in the picking crates should be as clean as possible (Photo 3). For that reason
they have to remove all undesirable material from the picking crates before these are delivered to the larger crush bins. It therefore makes
sense to have someone stand alongside the crush bin who can remove all undesirable material when the grapes are offloaded (Photo 4).Manual harvesting When manual harvesting takes place, it is critical to ensure that all harvesting equipment, such as shears, picking crates, bins and bulk crates, are thoroughly cleaned both before and after use. It is easy to clean the sticky grape juice and dust that cling to such harvesting
equipment by washing with lukewarm water and permissible cleaning aids (Photo 2).
PHOTO 1. Example of a press bin that is contaminated with MOG, in particular leaves and stems. PHOTO 2. A vineyard manager who ensures that picking crates are cleaned thoroughly on a daily basis after harvesting. PHOTO 3. A harvesting team should take care to ensure that the least amount of leaves, stems and shoots end up in the picking crates. PHOTO 4. An extra person to sort and remove MOG from the crush bin, could make a positive contribution to the wine quality. PHOTO 5. Examples of picking crates that were properly sorted in the vineyard PHOTO 6. A harvester with a thoroughly cleaned harvesting chamber before it enters a block. PHOTO 7. An example where a sorting machine is first used before manual sorting of grapes takes place on a sorting table.

Removal of MOG at the cellar
Mechanical wine grape sorting machines may also help to ensure the delivery of ‘clean’ grapes to the cellar. These machines use the latest
technology to remove undesirable material. Obviously such machines come with a hefty price tag. The use of sorting tables where grapes are on a conveyor belt and are sorted manually before progressing to the crushing cellar is also common practice in some of the wineries that produce high quality wines.  Mechanical wine grape sorting machines and sorting tables may be used either on their own or in combination (Photo 7).

Mechanical harvesting
Where mechanical harvesting is the order of the day, it is very important to clean the machine thoroughly beforehand and also after each
day’s usage. The settings of the harvester should also be appropriate to the specific block where it will be used. It may also be beneficial
to remove undesirable material, such as high weeds and poor quality grapes (e.g. rotten grapes), before the harvester moves through the
block. Obviously the use of clean bulk crates in which the grapes are transported to the cellar is also crucial, as with manual harvesting.

 

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