This is part 2 in an on going series about the basics of winemaking. If you haven’t already check out part 1 here.
Once you have your perfect vineyard site and the ideal growing condition for your grapes it will eventually come time to harvest. Just before harvest winemakers are in the vineyard almost daily running tests on the grapes and tasting them to determine the best time to pick. Two of the most important benchmarks that they are looking for are sugar content and tannin ripeness.
Lets start with sugar content, this is measured in Brix, for example someone would say that they want to harvest their grapes at 22 brix or 24 brix. Remember, the sugar in the grapes is what turns into the alcohol in the wine. So determining the level of sugar ripeness to pick the grapes at is a factor in determining the style of wine that you want to produce and the climate that the grapes are grown in. Warmer climates will produce grapes with higher sugar contents by default. Once the sugar ripeness is determined the next thing that winemakers will focus on is tannin ripeness. Tannins, as discussed before, are a naturally occurring component of grapes. They are present in the skin, the stems, and even the barrels in which wine is aged. Some varietals tend to have higher tannin content than others like Cabernet Sauvignon or Nebbiolo. Tannins also act as a natural preservative, which is why higher tannin wines can age for years on end and retain their structure and integrity. And in fact some of those more tannic wines need to age longer so that the tannins have a chance to mellow out and become less harsh and bitter. But it turns out there are two different kinds of tannins, ripe tannins and unripe tannins. Ripe tannins are what you are looking for because they produce a rich structured wine that is not overtly bitter, even when it is young. Unripe tannins produce wines that are harsh and have an intense dryness that overpowers everything else. And because they were unripe to begin with they rarely mellow out even with age. But how winemakers determine whether the tannins are ripe or not is not an easy or straightforward task. Unlike sugar content tannin ripeness cannot be measured or quantified. They only way to test for it is to taste the grape. The trick is to sense the tannin ripeness separately from the sugar ripeness.
Now that you have determined when to pick your grapes the next step is how. There are really two options hand harvest and machine harvest. While the romantic notion of a vineyard is that all the grapes are picked by hand that is not necessarily the reality. While hand harvesting definitely still takes place in smaller vineyards and with higher end/higher quality wines, machine harvest is becoming more and more commonplace in the wine industry. And as with any thing it comes with both some pros and some cons. One of the downsides is that a machine can never be as selective as a person – even though they are supposed to be calibrated to choose only the ripe grapes occasionally unripe grapes and other materials get picked as well. Machines can also be slightly less than delicate, meaning they can bruise or break the skins of the grapes or even break off parts of the vines themselves. On the other hand machines can operate 24/7 ensuing that when the grapes are ready to be harvested they are picked quickly, and that speed is critical when a vineyard is in a cooler climate or if bad weather is threatening the grapes. And finally mechanical harvest is considerably less expensive than hand harvesting. It is also important in wine regions that have a lack of labor available, most notably Australia.
Harvest, determining when to pick the grapes and how to pick the grapes, is yet another important winemaking decision that is made in the vineyard before the grapes even reach the winery. These decisions nonetheless significantly affect the outcome of the finished wine even though the actual process of making the wine has yet to begin.