D1: Harvest Flashcards
Choosing the date of harvest depends on:
1) the rule of thumb was that grapes ripened 100 days after the beginning of flowering
2) EU regions readiness for harvest has been measured by potential alc levels:
- - amount of all sugar in grape must into alcohol
3) in cool regions, once potential alc has reached 9-11%, the grapes could be harvested
- - AOC petit chablis: min 9.5
- - Chablis: 10
- - bourgogne blanc: 10.5
4) alc levels can be adjusted upwards by chaptalisation (within limits)
However, more recently the context for making decisions about harvesting dates has changed due to:
1) a generally warmer climate: making it easy to ripen grapes in cooler regions
2) better viticulture: enabling the vine to ripen succesfully
3) a focus on aroma and tannin ripeness
- - sometimes considered as more important than optimum sugar ripeness
One overriding factor is the threat of rain in the harvest period:
1) if rain is forecast, grape growers may have to choose between harvesting under-ripe fruit or risk leaving grapes on the vine
- - in hope the weather will improve
2) rain in last days before harvest can lead to diluting of juice or in worst case scenario, splitting of the skins due to rapid expansion, with consequent threat of grey rot and loss of some or all of the harvest
How to measure ripeness:
1) measuring various components in the grapes
- - in order to decide the optimum time of harvesting for the style of wine they are aiming for
2) Sugar levels: measured by a handheld refractometer:
- - most dry still wines are harvested between 19 and 25° brix
- —which convert into 11-15% abv
3) Aroma and tannin ripeness: usually determined by taste (with experience)
there are various wais of measuring other compounds:
1) tritration: calculate acid levels:
- - founding out an amount of a substance in a solution, by adding measured amounts of another substance that reacts in a known way
- —- similarly (vergelijkbaar) PH of the juice can be read by a ph Meter
2) high tech: visible or near infrared spectroscoop
- - gives multiple readings for sugar, acidity and various other wine compounds or measures
3) however tasting the grapes is one of the most important ways of deciding when to harvest
grape growers make choices about harvesting date, both in terms of the general issues covered in the preceding (voorafgaande) paragraphs and in relation to particular wine styles to be made for ex:
1) Loire: harvest chenin blanc over a period of 4-6 weeks
- - according to the style of wine to be made:
* early for sparkling
* mid for dry and off dry
* late for botrytis or late harvest styles
2) California:
* zinfandel early to mid august for white zinfandel
* september for red wine
* zinfandel tends to have ripe and unripe fruit at the same vine:
- - selection if high quality is required
* in hot areas the grape grower must decide wether or not to include shrivelled grapes
3) harvest of date important for winestyles with residual sugar:
some of these grapes are harvested late to concentrate the sugar in the grapes
* botrytised: often need handharvesting over several passes thrue the vineyard
* eiswein: temp below -8°C 18°f for canadian icewine
In South africa, even for low to mid priced wines, handharvesting is still possible, due the low labour cost.
Okido
In the past, machine harvesting used to be equated with only acceptable to good level quality wines. However several steps can be taken to improve quality today:
1) Selecting undesirable fruit by hand before harvesting by machine
2) using a bow rod machine which is gentler than oters, who beat the vine. this can be set to be more selective
3) Investing in the very lates machines, that have options for optical sorting devices on them, and which can crush white grapes and add so2 in the machine itself
4) rigorous (strenge) sorting on arrival in the winery, including removal of MOG (Matter Other than Grapes) and unripe and rotten grapes
What are the advantages of machine harvesting ?
1) Faster and cheaper in large vineyards (if they are designed for this)
- - study in california says: machine harvesting can be one-third of the price of hand harvesting
2) avoids issues of the lack of availability of, and possible unreliability (onbetrouwbaarheid) among, casual workers
3) grapes can be harvested at night and be kept up to 15°c 59°f cooler, than dayharvesting
- - can reduce microbial spoilage and oxidation
4) for white, fruity wines, starting the winemaking with cool fruit preserves the intensity of fruit aromas
- - also help to save the cost of refrigeration
5) the timing of the harvest can wait until the desired level of ripeness and then carried out quickly
- - by comparison, assembling and deploying a group of pickers may be less flexible and slower
What are the disadvantages of machine harvesting ?
1) less gentle than handharvesting
- grapes being shaken off the tems
- – potential leading to rupture of the grape skins and release some juice
- - so not so good if you wish to avoid oxidation or th extraction of phenolic compounds
- – for example with delicate white wines
2) It is not economic or practical for small scale vineyards
- - rental or ownership is not cost effective for small vineyards
3) may be unsuitable for grapegrowers, that have several different varieties ripening at a different time in the same plot (but it depends on the vineyard design)
4) not suitable for vineyards on steep slopes or with limited access
5) where an estate does not own its own harvester, there may be a competition for the rental of a machine at the moment of harvest
6) purchasing a harvester is a major investment
What are the advantages of hand harvesting ?
1) Pickers can be highly selective at a bunch by bunch level and to remove any diseased, under or extra ripe fruit at the point of harvest
2) deal with steeper slopes, irregular rows and mixed plantings in the same vineyard
3) if handled with care and put in small, stackable crates (with a max weight of 10-15k)
- - the crushing of the grapes and the release of juice, shich would then be prone to oxidization and to microbialspoilage, can be avoided
what are the disadvantages of hand harvesting ?
1) It is more expensive than machine harvesting in med to large vineyards
2) it requires the availability of a reliable work force and their training and supervision, to ensure that they work to the required standard
3) Harvest has to be carried out in daylight hours and may not be able to avoid high temp
- – this raises the chance of grapes being spoiled by microbes or oxidation
Some wine styles require hand harvesting:
1) premium sparkling wines, where whole bunches are required for whole bunch pressing
2) grapes for beaujolais, or other wines that will be made of carbonic or semi carbonic maceration
3) botrytis wines
Grapes are also hand harvested if they are on:
1) steep slopes (douro)
2) uneven land
3) bush vines
- - to be machine harvested, vines need to be held on a trellis
- – without the trellis, there would be too much damage to plants and the grapes
