As harvest is fast approaching, I thought I might write a series of blogs on the different tasks and aspects of harvest, or crush, as it is also referred to. Most winemakers will agree that this is the most crucial time in the winemaking process, with fermentation being the most crucial step. Of course, great wine cannot be made from mediocre fruit, but having a successful fermentation will definitely set the stage and make things go a lot more smoothly during the rest of the vinification process than starting out with unhealthy wine. For this reason, harvest can be a stressful time filled with both elation and woe for even the most seasoned winemakers.
image credit to wine folly.
The first step in the harvest process for most winemakers is walking the vineyards and taking samples. This way, the winemaker can get a sense of how the growing conditions are for that particular vintage, whether they are happy with the progress or whether they would like to see some extra attention from the vineyard manager, and how quickly the fruit is ripening. Once the fruit seems fairly close to being ripe, it enters a stage called veraison. Veraison is characterized by, among other things, skin color that has turned from green to the color it will be when ripe, a dimpling of the skin, softening of the berries, and seeds that start to turn from green to brown. Once veraison starts, either the winemaking team or the vineyard management team will start taking regular samples to be tested for sugar, acid, and pH levels. Using this information, together with the physical ripeness of the fruit, is how the winemaker makes the decision to pick the fruit.
Sampling is meant to be a comprehensive example of the entire vineyard block that will be harvested together. For that reason, samples should be taken randomly, from several different rows within the block, several different vines within the rows, and several different clusters within the vines. I will usually walk from one end of the block to the other, zig-zagging between rows, choosing vines instinctively, and averting my eyes as I pick berries from random clusters. Averting my eyes as I pick ensures that I will not just be picking the most attractive berries, because once the grapes are harvested and brought to the winery, there will be "perfect" berries and "less than perfect" berries together on the clusters, so to exclude the latter in sampling would not be a realistic example. Some people like to sample by removing whole clusters, and others by removing several berries from each cluster they sample from. Once you have enough fruit to get about half of liter of juice from, you can move on to the next vineyard block or varietal.
The samples are taken to a lab, crushed into must (a combination of juice and skins), and the juice is strained out. The juice is then tested for sugar content (measured in degrees brix), pH, and TA (titratable acidity, titration being the method of testing for measurable acid in the juice). These numbers are all considered together for picking decisions. Also considered is physical ripeness; how brown and hard the seeds are, how easy the berries the come off of the clusters, how much flavor and pigment are in the pulp, how soft the berries are, etc. Since brix content dictates the finished wine alcohol content, there is usually a range that a winemaker is trying to hit, depending on their style and the type of wine they are trying to make (ex: a dry sparkling wine will have less alcohol content, and a port will have more, than a table wine. Therefore, they will be picked at significantly different brix levels). pH and acid are secondarily important as you can always adjust the acidity up, however, it is very hard to adjust it down. Flavor is also important. Anyone who has picked fruit too early knows that you will have a potentially sweet taste, but it will be bland compared to a fully ripe piece of fruit. Sometimes nature plays nice, and all of these criteria are in line with each other and the optimal picking date is obvious; however, the reality is usually that one or two of these criteria will be out of range, and the winemaker has to decide which one is most important to base their picking date on. This is where experience and intuition comes in.
If you enjoyed this entry, stay tuned for the next entry in this series, where I will talk about harvesting the fruit.