Uso de nanoformulaciones para un cultivo más sostenible y de calidad de la variedad Monastrell

Abstract

This Doctoral Thesis is part of the "nano-VIT (RTI2018-095794-B-C21, RTI2018-095794-A-C22)" project, which seeks to optimise the application of urea and methyl jasmonate in vineyards in order to improve the quality of Monastrell grapes and wines. Previous researches have studied the foliar application of urea as a source of nitrogen and methyl jasmonate (MeJ) as a strategy to increase the synthesis of secondary metabolites in the plant. The results obtained have not always shown the expected effectiveness, which is why this Doctoral Thesis proposes the use of nanotechnology as an alternative to the conventional way of applying these compounds. Over the course of three successive seasons, an investigation was conducted to assess the impact of urea and MeJ application in two distinct modalities, conventional and supported on hydroxyapatite nanoparticles (nano-urea and nano-MeJ), on the quality attributes of Monastrell grapevines and the resulting wines. To this end, the effect of the different treatments on the composition of the cell wall, the phenolic composition (anthocyanins, stilbenes and proanthocyanidins) and nitrogen in grapes and wines was studied. Finally, the sensory quality of the wines obtained was evaluated. The research findings indicate that both conventional and nanoparticle treatments increased cell wall thickness. All treatments affected the structural components of the cell wall, increasing the contents of proteins, hemicellulose and uronic acids. On the other hand, phenolic compounds were not affected and cellulose showed lower concentrations than the control. Regarding the phenolic composition of grapes and wines, the results were different depending on the vintage and treatment. In the context of urea treatments, divergent outcomes were observed concerning the quantity of anthocyanins present in the grapes. Grapes treated with nano-urea obtained a lower concentration than control grapes. An inferior concentration of anthocyanins was also reflected in the wines from grapes of both treatments. As for stilbenes, the urea treatment caused an increase in their content in the grapes, although it was not transferred to the wine. The effect of the nano-urea treatment was not clear due to the disparity of the results obtained in the three years of study. The total proanthocyanidin content in grapes and wines was not affected by the urea and nano-urea treatments. On the other hand, the MeJ treatment achieved increases in anthocyanins in both grapes and wine when grapes achieved optimal maturity. However, such enhancements were not observed in the nano-MeJ treatment. Regarding stilbenes, both MeJ and nano-MeJ treatments showed increases in both grapes and wines. In contrast, total proanthocyanidins from the grape skins in the MeJ and nano-MeJ treatments showed lower values than in the control grapes, while the effect of proanthocyanidins from the seeds was different in the three years of the study. Finally, the content in the wines was not modified by the treatments. Turning to nitrogen compounds, all treatments caused an increase in both grapes and wines. These increments were more pronounced when the nitrogen content of the control grapes was initially lower. Finally, in the sensory evaluation of the wines obtained, the treatments with urea and nano-urea showed no perceptible differences compared to the control wine. In contrast, the wines derived from the MeJ and nano-MeJ treatments were discerned by the panelists as distinct from the control wine, with a preference expressed for the former. Therefore, in this Doctoral Thesis has demonstrated that, although the main factor influencing the variability of the results found was the vintage, both conventional and nanoparticle treatments are capable of producing variable effects on Monastrell grapes and wines. Moreover, conventional treatments produced more significant results than nanoparticle treatments. Even so, we must bear in mind that we have applied doses 8 (in the case of urea) and 10 (in the case of MeJ) lower than the conventional mode. Given that the results have not been totally satisfactory, it is necessary to optimise its application in order to improve its effectiveness and offer it to the sector as a new viticultural tool.