Changes in the volatile composition of wine from grapes treated with Bordeaux mixture: a laboratory-scale study

Background and Aims: We investigated the effect of the application of Bordeaux mixture in the vineyard on the copper concentration in the must, and the consequences for the volatile composition of wine. Methods and Results: Musts from grapes cv. Vinhao treated with Bordeaux mixture or with a triazole-based fungicide were prepared at a laboratory scale. Copper concentration decreased from 31.4 to 12.6 mg/L during fermentation, as determined by atomic absorption spectrometry. Increased copper concentration promoted a significant decrease in the concentration of higher alcohols, including isoamyl alcohol, and of esters of organic acids, including ethyl lactate, as determined by liquid-liquid microextraction Gas chromatography (GC)-flame ionisation detection and solid phase extraction GC-ion trap-mass spectrometry (MS) analysis. In contrast, the concentration of acetates such as ethyl acetate increased sharply, together with terpenes, namely linalool. Conclusions: The treatment of grapes in the vineyard with Bordeaux mixture shifted the aromatic composition of wine. Significance of the Study: Besides its scientific importance, the elucidation of how Bordeaux mixture affects grape and wine quality is of significant interest in oenology, especially in organic viticulture.