δ15N from soil to wine in bulk samples and proline

The feasibility of using δ15N as an additional isotopic marker able to link wine to its area of origin was investigated. The whole production chain (soil–leaves–grape–wine) was considered. Moreover, the research included evaluation of the effect of the fermentation process, the use of different types of yeast and white and red vinification, the addition of nitrogen adjuvants and ultrasound lysis simulating wine ageing. The δ15N of grapes and wine was measured in bulk samples and compounds, specifically in proline, for the first time. Despite isotopic fractionation from soil to wine, the δ15N values of leaves, grapes, wine and particularly must and wine proline conserved the variability of δ15N in the growing soil. Fermentation and ultrasound treatment did not affect the δ15N values of grape must, which was therefore conserved in wine. The addition of inorganic or organic adjuvants was able to influence the δ15N of bulk wine, depending on the amount and the difference between the δ15N of must and that of the adjuvant. The δ15N of wine proline was not influenced by adjuvant addition and is therefore the best marker for tracing the geographical origin of wine