Effects of urea and nano-urea foliar treatments on the aromatic profile of Monastrell wines

Abstract

Foliar application of urea has proven to be an effective method for increasing the amino acid content in grapes, especially when the vineyard has additional nitrogen needs. These treatments can prevent problems of stucking fermentation during winemaking. Furthermore, the synthesis of different aromatic compounds in wine is partially related to the content of different amino acids in must.

In this work, the effect over wine aromatic profile of foliar treatments with urea and nano-urea in Monastrell vineyards during two vintages, 2020 and 2021, was studied. Foliar treatments were applied at veraison and one week later: i) Control (water), ii) urea and iii) nano-urea. The aromatic profile of wines was analysed by solid phase microextraction (SPME) coupled to a gas chromatograph, using the methodology of Moreno-Olivares [1]. An organoleptic analysis was carried out in order to check whether there were organoleptic differences between control wines and those from the treatments.

Regarding to the results, in 2020 there was no clear effect of the treatments on the aromatic composition of wines, with a decrease in total aromatic concentration with respect to control wine in both treatments, being 14% for urea and 6% for nano-urea. This fall was mainly due to the lower values found in the alcohol family. In contrast, fruity esters were not affected in the urea treatment and increased in the nano-treatment by 12%. On the other hand, 3-methyl-thio-1-propanol was lower for the urea treatment by 17% and unchanged for the nano-treatment.

In 2021 for urea treatment, the effects were opposite to previous year, total aromas were increased by 24%, mainly due to the increment in alcohol family. Moreover, fruity esters were also increased. However, the behaviour of wines from grapes treated with nano-urea was very similar to that obtained in 2020, showing a 5% decrease in total aromatic composition. Both treatments presented a reduction in 3-methyl-thio-1-propanol compared to control wine, being 16% for urea and 51% for nano-urea treatment.

Finally, during the two years of the study, the organoleptic analysis showed no significant differences between the control wines and the wines from the treated grapes.

In conclusion, the aromatic profile of wines from grapes treated with urea and nano-urea revealed small changes, these variations were dependent on both vintage and treatment, also the sensory characteristics of wines were not modified.

References

[1] Moreno-Olivares, J.D., Giménez-Bañón, M.J., Paladines-Quezada, D.F., Gómez-Martínez, J.C., Cebrián-Pérez, A., FernándezFernández, J.I., Bleda-Sánchez, J.A., Gil-Muñoz, R.(2020). Molecules, 25, 3917.