9. Harvest Flashcards
How might a grower measure grape ripeness before harvest?
- Sugar levels
- Acid levels
- Aroma and tannin ripeness
How are sugar levels in grapes measured for ripeness?
The amount of sugar in ripening grapes is easily measured by a handheld refractometer.
There are a number of different scales, including brix, baumé and oechsle.
What is the difference between brix and baumé?
1 baumé=1.8° brix=18g/l sugar=1% potential alcohol.
At what level of brix/baumé are most dry still wines are harvested?
19°-25° brix
10.5-14.5 baumé
What is titration?
Titration can be used to calculate acid levels.
Titration is a method of finding out the amount of a substance in a solution by gradually adding measured amounts of another substance that reacts in a known way.
How can acid levels in grapes be measured before harvest?
Acid levels can be measured by titration
PH levels can be measured by PH meter
How can aroma and tannins be measured in grapes befoer harvest?
Only with taste and experience
What is near infrared spectroscopy (NIR)?
A high tech option that can give multiple readings for sugar, acidity and various other wine compounds or measures.
How might a grower improve quality when choosing to machine harvest?
- Selecting out undesirable fruit by hand before harvesting by machine
- Using a bow-rod shaking machine (rather than the older machines, which beat vines to remove the fruit); this is gentler and can be set to be more selective
- Investing in the very latest machines that have options for optical sorting devices on them and which can crush white grapes and add SO2 in the machine itself to limit oxidation
- Rigorous sorting on arrival in the winery, including removal of MOG (matter other than grapes) and unripe and rotten grapes.
What are the main advantages of machine harvesting?
- Harvesting by machine is faster and substantially cheaper in large vineyards, if the vineyards have been designed with this in mind. The proportions vary depending on the cost of labour and of machines, but studies conducted in California indicate that machine-harvesting can be one-third of the price of hand-harvesting.
- Machine-harvesting avoids issues of the lack of availability of, and unreliability among, casual workers.
- Grapes can be harvested at night and be kept up to 15°C cooler (than if they were picked during the day).
- The timing of the harvest can wait until the desired level of ripeness has been achieved and then carried out quickly..
What are the disadvantages of machine harvesting?
- Machine-harvesting is less gentle than hand- harvesting.
- Machine-harvesting may be unsuitable for grape growers that have several different varieties ripening at different times in the same plot.
- It is not suitable for vineyards on steep slopes or with limited access.
- The quality of the work is only as good as the skills of the operator.
- Rental or ownership of a machine is not cost effective for small vineyards.
- Where an estate does not own its own harvester, there may be competition for the rental of the machine at the best moment for harvest.
- Purchasing a harvester is a major investment.
What must a grower consider in regard to the quality and style of the final wine when choosing to machine-harvest?
Machine harvesting involves grapes being shaken off the stems (potentially leading to rupture of the grape skin and some release of juice), rather than keeping the bunches intact.
This is a consideration when making some styles of wine where whole bunches are required and when wishing to avoid any oxidation or the extraction of phenolic compounds, for example with delicate white wines.
What are the advantages of manual-harvesting?
- 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.
- Pickers can deal with steeper slopes, irregular rows and mixed plantings in the same vineyard.
- If handled with care and put in small, stackable crates (with a maximum weight of 10–15 kilos), the crushing of grapes and the release of juice, which would then be prone to oxidization and to microbial spoilage, can be avoided.
What are the disadvantages of manual-harvesting?
- It is more expensive than machine-harvesting in medium to large vineyards
- It requires the availability of a reliable work force and their training and supervision to ensure that they work to the required standard
- Harvest is most easily carried out in daylight hours and may not be able to avoid high temperatures; this raises the chance of grapes being spoiled by microbes or oxidation. (However, some producers hand harvest at night by providing their pickers with torches.)
In what scenarios is manual-harvesting required?
- When making premium sparkling wines made where whole bunches are required for whole bunch pressing
- Carbonic or semi-carbonic maceration require whole bunches for the process (for example, Beaujolais).
- If making a style of wine that requires selective harvesting of certain grapes (eg selecting only botrytis affected fruit for TBA).
- Vineyards located on steep slopes or uneven land are unsuitable for mechanisation, require manual harvesting
- Bushvines require to be manual harvested, as the canopy is not supported by a trellis
