How do you know when the winegrapes are ready to harvest?

At LangeTwins, we use a few different methods to determine when our winegrapes are at their optimal flavor and composition to produce our award-winning wines.

As harvest approaches, we begin taking “sugar tests”, or samples of berries from a particular vineyard block to measure, essentially, the content of sugar in the grape juice.  Remember that by the process of fermentation, sugars are converted into alcohol, so, the higher the sugar, the more potential alcohol your wine will have, depending on how your fermentation goes.  Taking a sugar test of the grapes is the most basic way of measuring the maturity of the fruit in the vineyard, but certainly not the only way.

Here’s how we do it:

First, we find a sucker who wants to work all summer in a dirty, sticky environment, taking sugar samples for us.  This year, that lucky individual is Michael VerHagen, a young man with significant agricultural experience from the Lodi area.

Michael samples berries in the vineyard cruising on his ATV, taking a representative sample of the fruit.  That means that he is taking three or four berries per cluster, from different positions on the cluster and the vine, and doing it throughout the vineyard. In a 10 acre vineyard, he might take three or four passes through, grabbing berries from clusters on the outside of vine, inside, high, low, and in different positions on the cluster (shoulder, wing, center, etc).  Michael then places these berries in a one-gallon bag.

Once back at the truck, Michael crushes the berries inside the bag, and pours the juice on the refractometer, a device to measure dissolved sugar-to-water mass ratio, or more simply, the percent amount of sugar in the juice. Read more about how a refractometer works here.

Looking through the eyepiece, we can see that the sugar level in this sample is 12 degrees Brix.   In general, winegrapes are harvested between 18 °Bx and 25 °Bx, depending on winegrape variety and goals of the winemaker.  But sugar is not the only measurement of a winegrapes maturity.  As we near harvest, we will use similar samples to measure the TA (total acid), pH, and perhaps some phenolic compounds to help us decide when a winegrape is at its peak of perfection to harvest.

Even though we have all of this fancy technology at our fingertips, we still employ the tried-and-true taste test and visual evaluation to decide when a vineyard is ready to harvest.

The color, texture, and flavor of the skins and seeds of the grape can easily override the empirical, objective data gathered through measurements.  Is it still tasting a little herbaceous?   Is that deep cherry flavor there that we want for this variety?  How about the seeds – soft, crunchy, flavor?  How does the vineyard look and do we think it can continue to support/improve the flavors of the winegrapes?

Our viticultural and winemaking team walk the vineyards and evaluate the fruit and vines before harvest to ensure that we are picking at the optimal time to make the best possible wines.

After all, the vineyard team works all year long for this moment, so it’s imperative that we  harvest the fruit at the right time, because amazing wines can only be made from amazing grapes.

Related posts:

1. Pics: Aaron’s best shots of Harvest 2009 so far
2. Pics: More of Aaron’s Shots from Harvest 2009
3. Two Golds, Two Silvers from the Grand Harvest Awards
4. Review: Randy Watson discovers our signature wine style

Tags: Brix, fermentation, grape maturity testing, pH, phenolic compounds, refractometer, viticultural team, wine style, winegrape sugar testing

This entry was posted on Saturday, August 8th, 2009 at 9:15 am and is filed under Harvest, In the Vineyards. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.