Determination of secondary metabolites as quality and typicalness tracers in autochthonous vitis vinifera grapes and wines from Ischia isle

The structural diversity is one of the most remarkable characteristics of proanthocyanidins (PA). Indeed, PA in wines may vary in the B-ring and C-ring substitutes, the C-ring stereochemistry, the degree of polymerization (DP) and the linkage between the monomers. Knowing in detail the structural characteristics of the PA of a wine can help us to understand and modulate several sensorial characteristics of the wine, such as color, antioxidant properties, flavor, and mouthfeel properties. In the last years was discovered and confirmed the presence of sulfonated monomeric and oligomeric flavan-3-ols in wine [1], as well as was pointed out their importance in wine quality [1,2].

The interaction between cultivar and growing environment is the base of wine quality and typicality. In recent time the behaviour of different clones within the same cultivar became another fundamental factor influencing the enological result. In order to clarify cultivar/clone/environment relations, a trial was carried out in 2008 studying the performances of three clones of ‘Nebbiolo’, grown in different environments: south-east Piedmont (hilly and characterized by a loamy and alkaline soil) and north-east Piedmont (a plain area characterized by a sandy and acidic soil).

Rotundone, the pepper aroma compound, has been detected in wines made from a large number of grape varieties. However, given the fact that analyzed wines were sourced from different winegrowing regions and seasons, made using different winemaking techniques and at different scales, it remains difficult to assess the real variety potential to produce rotundone.

Three compounds, 3-mercaptohexanol (3MH), 3-mercaptohexyl-acetate (3MHA) and 4-mercapto-4-methylpentan-2-one (4MMP), also known as varietal thiols, have been identified to contribute positively to wine aroma and are responsible for the distinct gooseberry, grapefruit, guava and box tree character found in Sauvignon blanc wines. Certain volatile thiol compounds though, can cause off-aromas of onion, garlic, rubber and rotten egg, this group of molecules is known as reductive sulphur compounds (RSC). This study looks into how the addition of sulphur-compounds to Sauvignon blanc juice contributes to the varietal thiol (3MH and 3MHA) concentration and reductive sulphur compound concentration in South African Sauvignon blanc wine.

Residual grape solids (suspended particles) in white and rosé musts vary depending on the clarification pro-cess. These suspended solids contain lipids (more especially phytosterols) that are essential for yeast meta-bolism and viability during fermentation in anaerobic conditions.