Harvest timing and postharvest dehydration duration affect grape and wine quality: A three-vintage study on Nebbiolo-based Sforzato di Valtellina DOCG wine production

The production of Sforzato di Valtellina DOCG wine (Valtellina, Italy) mandates a grape withering lasting at least till 1st December of the vintage year. Under these conditions, an earlier harvest will determine a longer withering duration. To understand the changes in fresh and withered grape quality, as well as on wines produced from them, the binomials resulting from the timing of harvest (early, medium, late) and the consequent mandatory natural withering period (long, medium, short) were tested in terms of basic chemical parameters, phenolic extraction from skins, seeds, and resulting in wine, and wine color. The study was replicated for three consecutive vintages and on two cv. Nebbiolo vineyards. The results indicate a shifted behavior in the juice sugars concentration from fresh samples (highest in late harvest) to withered grapes, although acidity was better preserved in early and medium-harvested grapes. Seed tannin extraction resulted highest in early harvested samples, even after dehydration. Wines produced from early harvest/long withering and medium-term harvest/withering where those preferred in terms of chemical features and color. Waiting for a late harvest has not given tangible advantages on the final wines, being even counterproductive in some cases because of a reduced grape health status.