Is it better to harvest by hand or machine? Caroline Gilby MW investigates
Rise of the Machines
Many of us like to imagine that grapes are picked by cheerful peasants, gently laying the precious bunches into wicker baskets before settling down to a hearty lunch in the vineyards.
Frequently wine labels proclaim 'hand harvested' as a sign of quality, but for most wines on the market today, and especially at the more price sensitive end of the market, harvesting machines play a huge role in bringing in the harvest.
Can you taste the difference?
However, it's not usually a question of quality, and few in the wine trade would be able to tell machine-harvested wines from hand harvested by taste - apart from making an educated guess based on style.
In the end, the choice of machine or hand picking is more often about practical and financial factors.
Sci-fi grapevine gazing monsters
Mechanical harvesters rather resemble some kind of sci-fi grapevine grazing monsters, as they straddle the vines and thwack their way along the rows, beating the vines with the help of rubber or fibreglass rods to shake or strip ripe berries from their stems (which usually remain on the vine).
These drop onto conveyors, which then deliver them to a trailer for eventual transfer to the winery. In more sophisticated machines, air blowers may remove unwanted leaves and shoots too, though inevitably some stray bugs and bits of vine will end up in with the harvest.
Research and development continues to move quickly - with techniques for selecting out healthy berries in progress.
A sixties development
Harvesting machines were originally developed in the 1960s in the USA but unionised grape pickers had blocked their commercial use. Their existence came to the attention of a researcher in Australia called John Possingham, who spotted the future potential of such devices and sent a colleague to acquire these prototype machines.
And so it was that Australia became the first major market for mechanical harvesters. By the early 1970s, it allowed producers to think big and go ahead with planting 200 to 400-hectare plots in the South Australian Riverland. Such vast vineyards would simply have been unfeasible to work without machines as there were no large population centres near enough to supply sufficient labour.
A technical solution to socio-economic issues
Machines are now common in most wine producing countries - and labour issues (availability, wage costs, welfare overheads, bureaucracy and even tightening of laws on employing illegal immigrants such as Mexicans in USA) have frequently been a driving factor in the rise of the machines.
And even in Eastern Europe where unemployment is high and labour is cheap (for instance a picker in Moldova may earn just 100 euros a month) workers often prefer to travel and work a succession of fruit and vegetable harvests in Spain or Italy rather than rely on a few weeks' work in the autumn for grape picking.
Distinct advantages of mechanical harvesting
Today's machines have come on a long way and nowadays producers recognise that mechanical harvesting has many advantages over old-fashioned hand picking.
One is that machines can pick large areas quickly at optimum ripeness, or perhaps before a weather front sets in, helping to prevent crop loss. It's estimated that a machine can pick a hectare of vineyard in no more than five hours, while hand labour could take between one and ten days to harvest the same area.
Machines can also run 24 hours a day, and importantly pick at night when it's cool - especially useful in hot regions. This helps to protect fruity aromas, slows down processes like browning that damage the juice and reduces the cost of refrigeration at the winery.
Indeed, research done in New Zealand in 2011 found that machine-harvested sauvignon blanc had higher levels of thiols, which are the aromatic compounds that give this wine its varietal character.
Of course there are downsides too: machines do cause more damage to vines and grapes through the physical trauma of dragging berries off stems, especially in fragile grape varieties like pinot noir.
This can be an issue if transport distances are long or in the heat of the day with grapes sitting unprotected in a soup of juice and dirt: extracting unwanted bitter phenolics; allowing premature oxidation and destroying delicate aroma molecules.
Most machines leave stems behind on the vines - which removes the need for a de-stemmer at the winery but also limits winemaking choices. Certain styles of wine require whole bunches.
For instance, in Champagne the traditional basket press relies on the gaps created by grape stems to allow juice to escape quickly. Special techniques like carbonic maceration require whole bunches (see Winemaking: More Secrets of Fermentation) and whole bunch pressing is often preferred by producers of fine whites.
Then there are cost issues: buying the machine can be 100,000 to 200,000 euros.
And finally many vineyards are simply not suitable, either because they are too steep or because the vine variety or training system is appropriate. Machines need neatly laid out, vertically-trained canopies on post and wires, and bear in mind that replanting a vineyard to suit could cost as much as 15,000 euros a hectare. Concrete posts are not ideal either as they crack easily, while machines can't cope with old bush vines or the pergolas so common in places like Italy's Veneto region.
Hand picking not just about romance
Many producers continue to pick by hand, and it's not just about romance and the right PR imagery but has very real benefits. Hand harvesting fruit into crates or boxes is undoubtedly gentler and limits premature damage to the fruit so it will survive long journeys in better condition.
Winemakers will have a full range of choices available to them - destemming or not depending on their wine style. Well-trained pickers can easily select healthy fruit as they go along, leaving unripe or rotten bunches behind.
And conversely, they can pick individual berries as required for certain noble rot sweet wines like Tokaji, Sauternes and Trockenbeerenauslese (read more about this in Winemaking: The Fungal Story). And people can hang on to steep slopes where machines cannot go, though in places like the Mosel Valley they may need harnesses.
Hand-harvesting: romance vs. reality
But choosing hand picking has financial downsides too - some estimates suggest hand picking costs 2-3 times as much per tonne as machine picking because salaries must be paid and often transport to bus in workers, accommodation and food have to be provided.
There are so many factors to consider in the complex world of winemaking and how grapes get from the vine to the winery, whether by hand or machine, is just one tiny part of the story.
Caroline Gilby is a Master of Wine and a scientist by training. She is a wine writer with a passion for the wines of Central and Eastern Europe and contributes to several wine books, magazines and websites