IMPACT OF MUST NITROGEN DEFICIENCY ON WHITE WINE COMPOSITION DEPENDING ON GRAPE VARIETY

Abstract

Nitrogen (N) nutrition of the vineyard strongly influences the must and the wine compositions. Several chemical markers present in wine (i.e., proline, succinic acid, higher alcohols and phenolic compounds) have been proposed for the cultivar Chasselas, as indicators of N deficiency in the grape must at harvest [1]. Grape genetics potentially influences the impact of N deficiency on grape composition, as well as on the concentration of potential indicators in the wine. The goal of this study was to evaluate if the che- mical markers found in Chasselas wine can be extended for other white wines to indicate N deficiency in the grape must.

This study was conducted on the vineyard of Agroscope in Changins (Switzerland) and focussed on four white grape varieties: Chardonnay, Sauvignon blanc, Gewürztraminer and Chasselas. Two treatments were set up (i.e, foliar N fertilisation at veraison and no fertilisation) for three years. Wine was produced for each treatment. The composition of the grapes was analysed at harvest and the potential indicators of N deficiency, mentioned above, were quantified in the wines. In addition, sensorial analysis of wines was carried out and highlighted the fact that wines from N-deficient must, regardless of grape variety, were less appreciated.

Nitrogen fertilisation significantly increased must N concentration (NH3 and amino acids (AA)) for all grape varieties, although the gain was related to the grape variety. Grape varieties influenced both the concentration and profile of AA in must. Nitrogen concentration in must was positively correlated with proline (R2 = 0.656) and propan-1-ol (R2 = 0.579) concentration in wine and negatively correlated with succinic acid, 2-phenyl-ethanol and catechin quantities in wines (R2 = 0.369; 0.368 and 0.266 respec- tively). Grape variety affected the concentration of all N deficiency indicators in wine (p < 0.05).

These results confirm that the chemical markers, initially proposed for Chasselas, can be used for other white wines. However, the threshold of the markers in wine, indicating N deficiency in grape juice, must be determined for each grape variety separately.

1. Dienes-Nagy, ., et al. (2020). Identification of putative chemical markers in white wine (Chasselas) related to nitrogen deficiencies in vineyards. OENO One, 54(3), 583–599