How do you know when grapes are ripe?

A couple of days ago, I was taking a group of American tourists round the beautiful cellars of Château St Jacques d’Albas in the Minervois when I was asked the seemingly simple question ‘how do you know when the grapes are ripe?’.

This is the question that is currently preoccupying every winemaker in Europe, and the answer is not straightforward. There are several factors that need to be taken into account: the chemical composition of the grapes, the physical changes in the grape, the health of the grapes and, very importantly, the taste.

The main components in the grape to measure are sugar and acidity. As grapes ripen, the sugar level goes up and the acidity goes down. Sugar levels can be simply measured by a refractometer. The reading in this pic shows a sugar reading of 14 Baumé which equates to a potential alcohol of 14%. Acidity is more difficult to measure and there are different ways of measuring it. But however it is done, the total acidity in the grape juice will give a good idea of the balance of the juice (and hence the wine) in terms of alcohol and acidity. Of course the ‘ideal’ sugar and acidity will vary according to the style of wine. Grapes destined for sparkling wine will be lower in sugar and higher in acid and those for a full bodied red wine.

Looking at the grapes gives clues to ripeness too. The grape pips turn from green to brown and the stems turn browner and become more woody. Assessing the health of the grapes is important. If there is grey rot then it may be best to harvest soon before it gets worse, even if the other indicators of ripeness are not there yet.

Tasting the grapes is vital. Every variety will develop its own flavours which indicate ripeness. A local oenologue who spent some time in Argentina tells me that Syrah tastes like Mate when it is ripe. I can’t remember what mate tastes like (and it’s not easy to get hold of in the Languedoc) but – note to self – I’ll have to try it again.

In an ideal world, all the indicators of ripeness would come together at exactly the same time. The 2013 vintage is a reminder that it doesn’t often happen like that as the harvest is so late and conditions at the moment are humid. At Domaine Lou Cayla we visit the vines daily to taste the grapes and assess the vineyard. We thought we would harvest this week but the acidity was too high and the flavours were not developed so we decided to wait as the grapes look nice and healthy. There is rain forecast for this weekend, so we are praying that it isn’t too heavy and that we will harvest next week under cloudless skies.

Talking of praying, here is a cute picture of a praying mantis, snapped in a trailer-load of Syrah grapes on their way to the co-op.