How and When Is the Best Time to Pick Grapes?

It is very difficult to determine the best time to pick grapes for making wine. As the grapes ripen acid levels drop while sugar, colour intensity and tannins increase. A wine’s acidity must be balanced against the richness it gains during ripening.

Winemaking begins when ripe grapes are delivered to the cellar but the ripening process in the vineyards needs to be monitored throughout the growing season and, particularly so, as the full ripening stage approaches.

How can you tell if the berries have enough sugar? Well, for one thing, you can taste the grapes. But winemakers also use a fractometer, which measures what is known as ‘degrees Balling’. As grapes approach a ripeness of between 5 and 7 °Balling below their full ripeness winemakers take samples to measure the progress of sugar and acid development. Although both of these measurements follow predictable curves they can vary slightly according to weather conditions.

While laboratory tests are important, the quality and condition of the fruit are best assessed by tasting. This can put a winemaker into a quandary. Sometimes the tasting tests and the lab results don’t correspond and the winemaker then has to make decision on when to actually pick. The decision will influence the wines eventual quality.

Grapes can arrive at the cellar in various containers depending on the method of picking used by the farms. The smallest containers are called Lug Boxes and are the most expensive to use. They allow gentle handling without breaking the berries. Larger containers called Pallet Bins or customized trailers can be used to handle large volumes but, as one can understand, they make it difficult to eliminate bad fruit or foreign bodies.

The fastest process is the use of mechanical harvesters, which pick grapes from their stems in the vineyards. However they break the fruit so there is no scope for selection. A plus in their favour is that they can operate at night or in the early morning and so avoid any spoilage from the sun, heat or excessive exposure to air.

When the grapes arrive they are weighed at the receiving depot and then go through the first stage of mechanical processing.