Sugar content of grapes by variety and what it depends on, table

The sugar content of grapes is more than just a number reflecting the sweetness of the berries; it's a key indicator that directly affects the taste of the harvest and its potential for further use. The amount of accumulated sugar determines whether a grape variety is suitable for fine wine, aromatic raisins, or fresh consumption. Sugar content is influenced by a complex set of factors, from grape variety and climate to soil composition and care. Understanding these nuances will help any gardener and viticulturist obtain a harvest of precisely the quality that perfectly suits their goals.

Let's get some concepts straight

There are indicators of "sugar content" or "sugar accumulation," which are very important in determining the quality of raw materials for further processing. Their content is made up of glucose and fructose, although by the time the harvest begins, other substances—galactose, ribose, maltose, raffinose, xylose, and others—also accumulate in the berries. On average, the figures range from 13-28%, with only some varieties reaching 40% when overripe. The quality of the harvest and its subsequent use depend on the sugar content.

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When describing a variety, the average sugar concentration is taken into account, but in reality it can fluctuate depending on ripening conditions, soil, rainfall, and sunshine. The berries reach their peak sweetness in the final days before harvest. For table wines, the berries are picked at full ripeness, for champagnes, a little earlier, and for dessert wines, a little later, allowing the grapes to overripe.

What does sugar content depend on?

This indicator depends on the variety and its characteristics. It's also important to consider several other factors that collectively influence the taste and sugar content:

• soil type (acidity, moisture, density, mineral composition);
• geographical location (climate, precipitation, altitude);
• insolation level (solar radiation indicator);
• proximity to water bodies;
• level of agricultural technology.

Growing region

The higher the average annual temperature and the number of sunny days in the growing area, the higher the sugar content in the fruit. Asian, Central Asian, and coastal regions are ideally suited for this climate, as their warm weather promotes better ripening and higher sugar content in grapes. On average, grape varieties grown here have a sugar content of around 30-32%. It's also worth noting that mountainous terrain favorably influences the flavor and sweetness of grapes. Mountains provide protection from strong winds and heavy rainfall, which also helps preserve the high flavor of the harvest.

Soil composition

Grapes can grow in any soil, but flavor, sugar content, and bunch size will vary greatly even within a single variety. Therefore, it's important to consider certain factors that will help produce a sweeter harvest. It's best to avoid planting wine grapes in black soil, as the high nitrogen content will result in vigorous stems and weak vine development. Mixed soils—sandy, sandy loam, loamy, and clayey—with silt, rocks, and organic matter are best. The key is to ensure the soil drains well and does not allow water to stagnate.

Water supply

To grow a good harvest With pronounced sugar content, it's important to consider the specific characteristics of this crop when watering. Optimal conditions include periodic watering during stem and leaf growth and no watering during the ripening of the bunches before harvest. It's important to maintain a balance whereby the plants receive sufficient moisture but are not subject to drought or waterlogging. Excessive moisture results in waterlogged berries without a pronounced flavor profile; insufficient moisture results in sweet berries that remain small. If the groundwater level is no deeper than 6 meters and the annual rainfall is at least 400 mm, vineyards can do without supplemental irrigation. In drier climates or with very deep groundwater sources, a supplemental irrigation system will be necessary. On average, soil moisture levels should be maintained at 70-75% to achieve satisfactory sweetness.

Determination of sugar content

Sugar content is determined using additional equipment, such as a hydrometer or refractometer. For combined samples, approximately 3 kg of grapes or 1 kg of pulp are required for chemical analysis using direct volumetric titration. To ensure that the analysis is averaged across the entire vineyard, berries must be picked from different vines, including those growing at the bottom, top, and center of the vine. If sampling is performed in the vineyard, a field refractometer is used. Measurements are taken three times over the 15 days prior to harvest, once every five days. Once technical maturity is reached, samples are taken daily. To obtain objective indicators of average sugar content, at least 10 samples must be taken at each site.

Types of sugars

There are three main types of sugars: glucose, fructose, and sucrose. Glucose is the least sweet of all, sucrose is slightly sweeter (1.45 times sweeter), and fructose is the sweetest (2.2 times higher than glucose). The ratio of these substances in the fruit changes as it ripens. Sucrose gradually forms in the green leaves and stems, then, as the berries begin to form, glucose appears in the pulp, initially accounting for about 80% of the total sugar content. Only with maturity does the fructose level increase, reaching approximately 50/50 ratio with glucose. If the vines are overripe, the fructose level increases at harvest due to the loss of excess moisture.

Sucrose in fruits is significantly lower than the main sugar-containing substances; its level directly depends on the amount of sunlight and heat received during stem formation. Slightly higher levels are found in varieties grown in America. Depending on the variety, the levels range from 0.04-0.4% in some, and 1.23-10.7% in others.

As berries develop color and sweetness, the sugars gradually break down, producing organic acids. About 90-95% of all acids are tartaric and malic, although glycolic, citric, oxalic, succinic, and other acids are also present in much smaller quantities.

Sugar content of grapes table

To determine whether sugar or acid needs to be added or reduced, you need to test the wort for sugar content and acidity. This requires additional equipment. However, at home, these aren't always readily available, so a table with average values ​​for each variety can serve as a guide:

Grape maturity and wine production

There's no single date for harvesting. Too many factors influence ripeness and timing—varietal characteristics, climate, the year's sunshine and rainfall, and what the harvested grapes will be used for. Whether the grapes are white or black, suitable for dry, table, or dessert wines, whether more or better quality grapes are needed—all of these factors dramatically change the timing.

It's impossible to determine ripeness by appearance, and even regular sugar tests don't provide a complete picture. If the vineyards are large, sometimes, to avoid the risk of losing the entire harvest, the harvest begins a little earlier to ensure all the berries are picked. The likelihood of rain must also be taken into account, as it will significantly affect the taste, adding a watery texture. Smaller estates, for whom high quality is more important, may age the vines longer to ultimately achieve higher sugar levels and use them for dessert wines.

Each type of wine has its own parameters, determined by its sugar and acidity levels. Different varieties and regions have their own indicators for full ripeness:

• for white table wines, sugar should be 16-18%, with acidity of 7-9%;
• for red table sugar, 17-19% is enough, with an acidity of 7-8%;
• for dessert grapes, the required level is 20-22% with an acidity of 6-7% (for such indicators, the grapes are kept on the branches a little longer, waiting for the so-called over-ripeness);
• To produce champagne, berries are harvested slightly before they reach technical maturity, so that they do not acquire excessive sweetness.

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The hotter and drier the climate, the earlier the harvest begins, often with the berries still slightly unripe. In northern regions, it takes a little longer for the fruit to acquire the desired sweetness. However, don't over-ripen the grapes, or you'll end up with overly strong, cloying wines.

Acidity and sugar content

In addition to sugar, grapes contain numerous acids, two of which are the most abundant: tartaric and malic. Their percentages are important to winemakers, as variations in their amounts can create completely different flavors, lending the unique charm of certain wines. This is especially important for white varieties. On average, these levels should be between 7-10 g/liter, with the exception of specialty wines. Some winemakers focus more on pH (hydrogen peroxide), which ranges from 2.7 to 3.7. pH indicates the presence of non-volatile acids that affect flavor, while total acidity measures all possible acids, including those that evaporate over time.

Tartaric and malic acids have completely different characteristics: the former is soft and has a pleasant flavor profile, while the latter is harsh and angular, imparting a boldness to young drinks. Well-known brands with a high content of malic acid are: Pinot NoirMalbec. In winemaking, there's a concept called a "harvest year," which partly depends on the malic acid content of the vines at any given time. The cooler the summer, the higher the malic acid content, meaning the harvest will be of poor quality, and vice versa. In red wines, malic acid is converted to lactic acid, softening the overall flavor.

Conclusion

Sugar content and acidity are two important variables in determining the start of the harvest and subsequent use of the grapes. While there are established standards for a given grape variety, these vary each year depending on rainfall, sunshine, and other factors. Winemakers determine the success of the season by analyzing these parameters and comparing them with previous years.