Harvest time – so how do we know when the grapes are ready to be picked?
Blog Tsouris Wine Winemaking
It may seem pretty obvious, but in fact a great deal of care needs to be taken to ensure the grapes are ripe for the particular wine you plan to make. We started our harvest this year in early September, as the first of our grapes became fully ripe. So, what exactly is ripeness in grapes and how do we test for it?
What happens to grapes as they ripen
The evolution of a grape starts with flowering (usually in early May) and as the flowers pollinate and the grapes form they begin their lives as tiny, green berries tucked in close to the main body of the vine. As the summer progresses and the sunlight and warmth permeate the vine, the tiny berries begin to grow in size and weight and start turning from green to red (in the case of red grapes). In France, this moment is known as véraison – meaning “the onset of ripening”.
During this phase there are lots of things going on inside the grapes. As the leaves drive the photosynthesis engine of the vine, the sugars begin to develop in the grape and the acids begin to decline. The berries turn from small, hard, acid bombs to softer, sweeter, and altogether more desirable fruit (a favourite snack for the sangliers – the wild boars of the region who love to feast on grapes – more on sangliers in a future blog).
But just because the grapes seem ripe to the sangliers, doesn’t mean the are necessarily ripe from an oenological (winemaking) perspective.
There used to be a traditional view that the grapes would be ready for harvest 100 days after the onset of flowering, but these days we are a little more scientific about the optimal time for harvesting.
What do we mean by ‘ripe’?
In winemaking, we look at several factors in order to determine whether grapes are ready for picking.
The style of wine we are making is the main consideration (early picking for higher acidity and later picking for higher sugar content). These are the different elements we look at:
The sugar ripeness. This dictates the strength of the alcohol and the dryness (or not) of the final wine. In Provence, both the level of the alcohol and of the residual sugar is mandated by the AOC.
The acids, to see whether they have dropped sufficiently low to provide a balanced wine but still enough to provide a little bite (one of the characteristics that makes the rosé such a versatile food wine is the right combination of the right types acidity). There are several different acids present in wine.
We also look at the overall physiological ripeness (colour of skin and pips, the taste of the grapes, tannins etc.). If the tannins are under-ripe (or green) these can lead to unpleasant bitter flavours in the finished wine.
Technology lends a hand
Nature isn’t always (indeed, isn’t often) on the side of the winemaker, so we look long and hard at the final stages in the development of the grape to try and pick the best possible moment for picking. The sugar levels are usually measured in the vineyard with a small, handheld instrument called a refractometer (see picture).
These days we tend to lean on technology more and more and we use more advanced laboratory technology to measure the overall state of a grape’s ripeness; so we’ll also send samples of grapes from various parts of each vineyard plot to the lab for a detailed analysis.
Often the easiest way is to just taste
But of course, the best way to get an overall impression of the grape’s ripeness is by using our good, old-fashioned senses, taste and smell. But even picking grapes by hand from around the vineyard needs to be done in a methodical way, as bunches of grapes from the same plot (or even the same vine) will ripen at different rates, depending on several factors, including whether they are exposed to the sun, covered by foliage etc.
So, once the winery has agreed that the grapes are ripe for picking, the harvest begins. These days, thankfully, we just pick up the phone to the guy who drives the machine harvester and the vendange begins.