Winemaking: Managing Your Harvest and Fermentations

Harvest is that magical time when the baton is handed from the grape grower to the winemaker. The crop has been carried from bud break through flowering, fruit set, veraison, and maturation. For the last stretch of this process, the winemaker should be in the vineyard frequently, in close contact with the grapes with which they will be making wine. Selecting the correct picking date can be the difference between making an incredible wine or merely an acceptable one.

The question is how do you know when the grapes are ready to harvest?

What we look for in the vineyard is complicated, multi-fold, and subjective. Depending on the style of wine you are making, the sugars and acids will have arrived at a cross point of balance between pH and sweetness that is to your liking. The flesh/skin of the grape should be firm, yet supple, not dehydrated. The juice inside will be sweet rather than tart. The pips/seeds should be browning, if not brown.

We are looking for a sweetness level of about 25-26 brix for most table wines. The ratio of sugar to potential alcohol is about one-half. A measure of 26 brix should result in a wine of about 13% alcohol by volume (abv).

The pH of the must/juice should be in the range of 3.1 – 3.75. A simple testing kit is helpful for measuring pH. Green grape must typically falls on the lower side of the scale. Black grape musts will be closer to the high end. The simplest way to think about it – the closer the number is to 3, the more tart the wine will be.

There are variations to this assessment for each variety and every winemaker, not to mention every vintage.