How do we know when the grapes are ready to pick?

It’s time to pick the grapes! The big question is how do we know when the grapes are ready? Can you tell by look or by tasting them? Are mind-straining mathematical equations required? Or do one of those little tiny birds in the vineyard let us know?

Well, it’s actually all of the above and more.  Here’s a rundown of the things that we monitor prior to harvesting:

Critters
Birds, wild turkeys, raccoons, and other wildlife like to eat grapes – specifically, ripe grapes. When we see the birds getting more active in the vineyard, this is our first sign that harvest will be soon. This is when our modern-day scarecrow, the inflatable dancing tube guy we call Coo Coo Cachoo, gets to make his debut. His job is to scare those critters away until we harvest the grapes.

Coo Coo Cachoo, our modern-day scarecrow

Color
We want the grape berries to be rich in color, but not green. Even though the color has turned, it doesn’t always mean that the grapes are ripe. In general, grapes can need a few weeks to a few months more of hang time after they have turned color. The timing of this depends on the grape variety, the weather, and what type of wine you are making.

We also look at the color of the stems and seeds. In many varieties, the stems will go from green to brown, which is another indication of ripening. The same thing will happen with the seeds – they will go from green to brown when the grape ripens. We further test the seeds by chewing them. The seeds will break easily when the grapes are ripe.

Seeds at top are brown, seeds at lower right are green and tan. Seeds at bottom left are brown in the middle.

Touch
The grape berries start out as small, hard green berries. As they mature, the berries will swell. A ripe grape is plump and juicy. It will crush easily. If it is overripe, it will begin to shrivel up like a raisin. Another sign of ripeness is that ripe grape berries can be pulled from the grape cluster easily.

Plump, juicy grape

Taste
When grapes first develop they are small and filled with acid (think super bitter). As they mature, sugar is transported from the leaves into the fruit. The grapes will swell with increased water that will dilute the concentration of acids. In addition, the flavor compounds and tannins will increase. Each variety of grape has its own special flavors to look for. When the grape is fully ripe, we will taste those varietal flavors.

Whether tasting grapes, or doing any of the many other tests we do to evaluate ripeness, it is important to get many samples because not all grape berries ripen at the same time. Grapes that get more sunshine typically have higher sugar levels than those that might be slightly shaded. In August, you’ll find our winemaker, Mark Wenzel, and his vineyard crew taking daily romps through the vineyard sampling grapes from all over the vineyard.

The Numbers
Yes, there are some numbers involved when evaluating grape ripeness so it means we have to head to the laboratory for some testing. As the grapes ripen, sugar and pH increase as total acidity decreases. Finding the right sugar-acid balance is very important for making wine. For sparkling wines, we are looking for lower sugar levels and higher acid levels than grapes that will be used for still wines.

Sugar is measured using what is called the Brix scale, which is the percentage of sugars in the grapes. Sparkling wine grapes are typically harvested when Brix is 18° and 20° Brix; grapes for still wines are typically harvested when Brix levels are between 19° and 25°. Brix levels are measured using two different tools. With the refractometer, the juice of the grapes is squeezed into the refractometer plate and the instrument is held toward the light. The sugar reading can be seen through an eyepiece. The other tool used to measure Brix is the hydrometer. This tool requires more grapes, but is more accurate. We float the hydrometer in the grape juice and the sugar content is identified by the scale on the hydrometer. We use both methods as we get closer to harvest.

We look at both the pH level and the titratable acid (TA) level when evaluating acidity; both of these values change from vintage year.  As the grapes ripen, the pH level will rise and the TA level will drop.  Using a pH meter, we want our pH values to be between 2.90 to 3.20 so that the yeast can ferment the sugars. These target pH levels are also important because they enable our wines to be held in more stable conditions from the time we finish our first fermentation to the time we bottle for our second fermentation. The TA levels vary depending on the style of sparkling wine we are making.  For our wines made in the brut style, we are looking at TA levels of 9 to 11 g/L and for our wines made in the sec and demi-sec style we look at TA levels from 11 to 15 g/L.

Sarah using the refractometer to measure Brix (sugar level).

In the lab, measuring TA, pH, and Brix.

Summing it all up
As you can see, quite a bit of thought goes into determining when the grapes are ready to pick. Each year, we keep notes on the numbers, the dates we harvested, the appearance and taste at the time of harvest, and even the weather during the growing season. Over time, we get a better idea of what numbers and characteristics we need to look for to make sure we are harvesting the grapes at the optimal time for us to produce high-quality wines.

And while many wineries are now harvesting their grapes by machine, we feel it is important to do it the old-fashioned way – by hand. Machine harvesting of grapes shakes the berries off the stems, and allows some of the precious juice to escape. For sparkling wine, we whole berry press to get the premium juice from the grape, which is the first juice that is released from the grape. So we hand pick. It’s hard work, but we know it’s worth it.

www.illinoissparklingco.com