Grapes with Perfect Sweetness

When is the right time to harvest grapes? An important parameter determining when the best time to bring in the harvest is the sugar content of grapes. It can be checked directly in the vineyard using the METTLER TOLEDO Density2Go™, a high-precision portable density meter.
 
Grape harvesting is the first of many stages of winemaking. At the Swiss Arenenberg Vineyard, grapes are harvested in September and October. During these months, Peter Mössner, vineyard and cellar master, goes into the vineyard daily to measure the sugar content of the grapes and determine how ripe they are. And since last year, the Density2Go™ portable density meter is always at his side.

Interplay between Sugar and Acid

Each grape variety has its own individual ripening period, during which time the grapes store solar energy in the form of sugar. Since the areas north of the Alps receive fewer hours of sunshine than those in the south, early-ripening grape varieties, such as Müller-Thurgau, are usually grown here. This is also the case at Arenenberg, where Pinot noir and Kerner grapes are pressed alongside Müller-Thurgau on the over seven-acre (three-hectare) estate. “The optimal degree of ripeness for each of the grape varieties is one of the most important factors that will influence a successful vintage, which is why it must be constantly monitored,” explains Peter Mössner. “When the weather is dry and sunny, the sugar content in the grapes increases rapidly, while the weight of the grapes decreases rapidly.”

The concentration of fructose in the growing grapes is measured in different units depending on the country.  The Density2Go can measure in various units such as Oechsle degrees, Brix, and many more to meet your needs. Generally, the riper the grape, the higher its sugar content. The value provides information about the future possible alcohol content of the wine, since during fermentation, the sugar is converted into alcohol by the wine yeasts. In northern regions that receive just a few hours of sunshine, a high fructose content is a sign of quality. However, a high sugar content decreases the acidity in the grapes. For elegant, full-bodied wines, it is precisely the interplay between sweetness and pleasant acidity that is important. Experience and intuition are therefore required of the winemaker to find the optimal harvest time.

Sugar Concentration via Density Measurement

In addition to knowledge, accurate measurement data are crucial. Since last year, winemaker Peter Mössner has been relying on the Density2Go portable density meter to measure sugar concentration with the highest Swiss quality.  “The Density2Go is lightweight, handy, and user-friendly,” states Mössner. Since it can be conveniently operated with just one hand, it simplifies work in the vineyard. “For the measurements, we simply crush a few grapes and pour the juice into a small vessel. The device determines the sugar content in seconds."

However, the uses of the Density2Go in winemaking go even further; the compact device also plays a major role in monitoring fermentation. After harvesting, the grapes are crushed into must -- a mixture of skins, seeds and stems. The grape must ferments in the wine cellar for one to two weeks. The cellar master then mixes pure yeast cultures into the must. The yeasts convert the sugar into alcohol and carbon dioxide. This is a delicate process that must be closely monitored. The faster the fermentation, the more flavors are drawn out by the carbon dioxide. On the other hand, undesirable interruptions of fermentation need to be prevented.  To intervene quickly if necessary, the cellar master takes daily measures of the decrease in sugar concentration. What is his tool of choice? The Density2Go, of course.

Would you like to learn more about wine production at the Arenenberg Vinyard? Then watch the video: