The Impact of Grape Harvest on Fermentation Process and Red Wine Quality

Harvesting is one of the most important technological decisions in wine production, as its timing largely determines the initial chemical, microbiological, and phenolic potential of the raw material, thereby influencing the fermentation process, extraction of color and tannins, and the final sensory profile of the wine. To produce quality red wine, it is necessary to achieve appropriate levels of sugar, alcohol, total and individual acids, primary aromas, anthocyanins, and tannins. In warm, dry years, which have been common in recent years, grapes may reach high sugar content while acids decrease, but seeds and skins may still impart pronounced green, coarse, or aggressive phenolic characteristics. Delaying harvest to achieve better phenolic ripeness carries the risk of excessive sugar accumulation, high alcohol levels, elevated pH, and loss of freshness. Additionally, grapes that have ripened under significant heat and water stress may have unfavorable fermentation potential, requiring laboratory analysis and, if necessary, nutrient adjustments. The optimal temperature at the start of fermentation for red wines is 18-20°C (measured in the must). Allowed enological additives (such as sulfur dioxide, yeasts, enzymes, yeast nutrients, etc.) should be used. Implementing parcel-based harvesting—harvesting earlier in vineyard sections with suitable conditions and leaving other parts for later—is recommended.