(A) Traditional Method of Deciding the Right Harvest Date
In the olden days, grape picking was set 100 days after flowering. In places like Europe, however, there were legislation that dictated harvest based on specific geographical locations. French had the AOC (Appellation D’origin Controlee). This is a label that identifies tradition, the concept of Terroir and quality. For instance in the olden days, AOC Minimum Alcohol Regulation dictates the in the cool region of Burgundy, France. Once the potential Alcohol By Volume content (ABV) of the Chardonnay grape variety reaches a minimum of 9.5%, the grapes could then be harvested and can be classified as Petit Chablis. When ABV reaches a minimum of 10%, it is classified as Chablis which is the higher step from Petit Chablis. In warmer areas where ABV can reach a minimum of 10.5% ABV due to the fact the grapes end up becoming much riper, the Wines are classified as Bourgogne Blanc.
(B) Harvesting Done Today
Today there is a much more in-depth understanding of viticulture where grape growers can get the vines to ripen grapes more fully. There is more focus these days on riper aromas and tannins than just high sugar levels. Grape growers are at the disposal of newer harvesting machines which can help pick grapes and get them into processing in much healthier conditions where winemakers can extract the optimum goodness from the grapes . There is also the strategic and much better use of fungicide, where rotting of the grapes and botrytis is mitigated without its excessive use. Improved canopy management where foliage is managed to allow for better airflow and reducing the chances of fungal diseases. This way, grape growers are more confident to leave the grapes on the vine for longer periods of time and extend the ripening times.
However, in the risk of forecasted Rains closer to harvest, Grape growers will need to decide whether to harvest the under ripe grapes that are high in Methoxypyrazine and lower sugars. Or take the risk and leave the grapes on the vine for more time in the hope that the weather would change for the better.
HARVEST DATES FOR SPECIFIC WINES STYLES
The harvest time of Chenin Blanc in Loire, France is approximately about 4-6 weeks. For sparkling wine production, harvest is typically done early September. For the drier and off dry styles , harvest is done during the later periods. Botrytis affected sweet styles of wines also see a delayed harvest to intensify sweetness and harvest before picking. Chenin Blanc is known for its uneven ripening, so several passes through the vineyard during harvest season is required for quality assurance. This is critical for picking Botrytis-affected grapes for sweet wine making.
German Riesling is another example of white wine variety where time of the harvest determines the style of wines. Dry Style (Trocken),Late Harvest (Spatlese), Late Harvest with Noble Rot (Beerenauslese).
Californian Zinfandel is another example. As this specific variety is known to have both unripe and ripe fruits on the same bunch, a lot of care has to be taken for a high-quality wine. In warmer parts of California, there is always the option whether to utilise shrivelled grapes for higher alcohol wine or a potential wine with more residual sugar in the final wine. White Zinfanel which are rose wines are generally zinfandel that are early harvest. This helps the variety to retain its acidity and freshness that fits the style for rosé wines.
Vendange Tardive which is a style of French Dessert wine, where the grapes are left to hang on the vines until they start to dehydrate and concentrate sugars in the must. This also changes the overall taste profile of the resultant wine. On the other hand, botrytis affected grapes will undergo several passes through the vineyard, where the grape pickers are trained to pick the most botrytis affected grapes during each passing, making the harvest process during certain vintages last for weeks.
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