Sorting Tables: Hand Sorting vs. Optical Sorters

Sorting is a quality step at the winery. As Wine Spectator puts it, freshly picked grapes entering the winery have to be sorted for quality, a process commonly known in French as triage. The AWRI's 2015 review of the equipment defines sorters as devices that remove further vegetal matter (stem fragments, petioles and leaves), other contaminants such as insects, or undesirable grapes and parts of grapes, such as diseased or unripe grapes. The AWRI uses the term matter other than grapes (MOG) for the non-grape material that finds its way into picking crates or bins, whether grapes are hand-picked or machine harvested.

• MOG can include leaves, petioles and canes, as well as stones, sticks, strainer wire, caterpillars, millipedes and stink bugs (AWRI)
• Hand sorting is typically done on conveying tables that spread the grapes and present them to the people sorting; belt conveyor tables and vibrating conveyor tables are both used (AWRI, 2015)
• An optical sorter recognises anything that does not have the desired size, shape and colour and blows it onto another conveyor belt with a blast of air (Wine Spectator)
• Mechanical harvesters still cannot distinguish as well as humans between ripe, underripe or rotten grapes, leaves, dirt and bugs, which Wine Spectator says increases the need to sort machine-harvested fruit

On a hand-sorting line, Wine Spectator explains, the grapes usually travel down a conveyor belt past a line of sorters making the selections, and the belt often vibrates to shake out bad grapes hiding under good ones. Once the best grapes have been selected, they go on to be crushed. The AWRI notes that manual sorting may be carried out before or after destemming, while automated sorters are only employed after destemming. In an optical sorter, the AWRI describes a pre-draining screen, after which the material is spread and imaged; the images are processed and defects are removed by valved air jets across the width of the sorter. In some low-throughput devices (under 5 tonnes per hour) the material is imaged and defects removed while it falls by gravity, while in higher-throughput equipment (around 10 tonnes per hour) the material is spaced out and imaged on a high-speed conveyor belt and defects are removed as the material is projected off the belt (AWRI, 2015).

• Optical sorter software can use parameters such as shape in addition to colour to distinguish objects; the AWRI reported in 2019 that one model, the Raytec Vision Dionysos, also detects vegetal matter in the near-infrared based on chlorophyll excitation and fluorescence
• When a defect is identified, a specific valve opens and shoots a jet of air to reject it into a waste bin; the CITF Alien sorter instead uses delta robots to move a hose to the defect and vacuum it away (AWRI, 2019)
• The Dionysos allows three-way sorting, with defects removed into two bins, so over-ripe grapes could be kept separate from MOG and still be made into wine (AWRI, 2019)
• Density bath sorters work on a different principle: whole berries roll into a sugar or juice bath of set density, where ripe grapes sink and unripe grapes and other debris float (AWRI, 2019)

The AWRI's 2015 review says whether sorting is worthwhile depends on many factors, such as wine style, price point and grape condition, and that whether white or red wine is being made is likely to make a big difference to the effect of residual vegetal matter. For white wine, only very high levels of vegetal matter might be expected to affect quality, since juice and vegetal matter are typically in contact only very briefly before pressing. For red wine, residual vegetal matter is more likely to affect quality because it stays in contact with the juice and wine during fermentation. The same review cites earlier research (Vinsonneau and Vergnes) reporting that 1% residual vegetal matter can have a negative impact on quality for some red wines.

• AWRI-cited research on Shiraz (Capone et al., 2018) found that leaves alone did not contribute to green flavour, while stems were a bigger contributor to green aroma character and increased methoxypyrazine concentrations
• Wines made with added stems in that study were also rated higher in astringency, colour intensity and acidity (AWRI)
• Damaged fruit is likely to carry much higher populations of microorganisms such as acetic acid bacteria and oxidative yeast, and Oregon State University Extension lists sorting fruit prior to processing among its tactics for dealing with damaged fruit
• In trials of sorting equipment cited by the AWRI (Anneraud et al., 2012), vegetal matter before sorting ranged from 0.4 to 1.7% and residual vegetal matter after sorting from 0.1 to 0.4%, with grape losses of 0.2 to 4%

Wine Spectator notes that most mass-produced wines are now harvested mechanically, which is less expensive and faster but increases the need to sort the grapes. In Australia, the AWRI's 2016 survey found that smaller wineries were more likely to perform some sorting than larger ones, and hand sorting of bunches was the most common technique. The AWRI suggested in 2015 that the small number of automated sorters in Australia could reflect the limited amount of manual sorting there relative to some other regions of the world, which makes capital investment in automated equipment difficult to justify because there are no labour savings to offset it.

• Among Australian wineries crushing more than 10,000 tonnes, use of roller sorting has risen since 2016 from 4% to at least 16%, according to the AWRI's March 2019 update, typically only for more premium grapes
• The AWRI called the benefits of sorting white grapes debatable in 2019, since any solid contaminants in the load are removed during draining and pressing shortly after arrival at the winery
• Destemming and sorting can also happen on the harvester; in 2016, 6% of red and 5% of Australian machine-harvested white grapes (by hectare) were destemmed on-harvester (AWRI, 2019)

According to the AWRI, optical sorting trials on winegrapes were first reported by Falconer and Hart in 2005, and equipment has been available from wine industry suppliers since around 2008; by 2019 numerous suppliers sold optical sorters to the wine industry, including Bucher-Vaslin and Pellenc. In Bordeaux, a Decanter harvest report by Jane Anson and Panos Kakaviatos (page last updated 2015) described Château Pavie working with a new sorting table that removes the stalks far more gently than previous generations of machines and then passes the grapes through an optic camera to eliminate those without pre-determined quality factors such as sufficient must weight. Decanter reported that this new breed of sorting machines started at around €100,000. The same report noted that at Château Léoville Barton the harvest was dropped onto a single sorting table before machine de-stemming.

• The AWRI's 2016 survey found optical sorting at only 1.5% of Australian wineries crushing more than 50 tonnes, against roller sorting at around 6%
• Château Pavie owner Gérard Perse told Decanter: "In five years, the idea of manual sorting will be unthinkable"
• At Château Angélus, Decanter reported 50 gloved workers de-stemming the bunches grape by grape, and owner Hubert de Boüard said the almost entirely unscathed grapes made sorting tables almost redundant
• At the 2018 Vinitech-Sifel show the AWRI reviewed the Raytec Vision Dionysos, which costs around $250,000 and according to Raytec can process around 8 t/hr, and the CITF Alien, which CITF said can remove 400 defects per minute (AWRI, 2019)

The AWRI's 2015 review describes manual sorting as slow and highly labour intensive, requiring great concentration. On the equipment side, density bath and optical sorting systems were significantly more expensive, about 5 to 10 times, than the more basic mechanical sorting systems, but offer more sophistication when trying to remove very unripe or diseased grapes and contaminants rather than just vegetal matter. The review adds that the performance of sorting after destemming will always depend on the condition of the grapes and the gentleness of the destemming process, and is likely to be reduced if the grapes have been broken down too much.

• The settings that determine which material an optical sorter removes can easily be modified using software (AWRI, 2015)
• A basic density bath sorter, the SOCMA Densibaie, costs around $40,000 with a nominal maximum flow rate of 4 t/hr, the AWRI reported in 2019
• Roller sorters allow reasonably high throughputs, in the order of 10 t/hr, for their price, and newer Pera-Pellenc and Bucher-Vaslin systems reach the order of 50 t/hr (AWRI, 2019)
• The AWRI noted in 2019 that as with most sorting systems there are likely to be other required peripherals and associated costs

Primary sources: https://www.awri.com.au/wp-content/uploads/2019/01/Nordestgaard2015-DestemmingSortingPart1and2.pdf, https://www.awri.com.au/wp-content/uploads/2019/04/Nordestgaard2019-GrapeSorting.pdf, https://www.awri.com.au/industry_support/winemaking_resources/winemaking-practices/winemaking-treatment-matter-other-than-grapes-mog/, https://extension.oregonstate.edu/crop-production/wine-grapes/dealing-damaged-fruit-winery. Secondary sources: https://www.winespectator.com/articles/wine-harvest-101-basics-of-crush, https://www.decanter.com/wine-news/lasers-to-overtake-manual-sorting-in-hi-tech-bordeaux-64473/, https://www.winespectator.com/articles/how-is-wine-made-basic-winemaking-steps-explainer. Last verified 2026-09-28