Effect of topographical conditions on the amino acid content and the yeast-assimilable nitrogen concentration on the red Mencía cv. in the D.O. Ribeira Sacra (Northwest Spain)

Abstract

Ribeira Sacra is a Spanish DO located in Galicia (NW of Spain). Mencía is the most important red grape grown in the region. Most vineyards in the region are terraced due to the steep slopes that characterize the region. The aim of this research was to perform the effect of vintage, elevation and exposition on the YAN (Yeast Assimilable Nitrogen) and amino acid profile in Mencía grapes. Fifteen plots of Mencía were chosen over a distance of 120 km. Phenological development, nitrogen status and grape maturation of vines were monitored. A four-year study was conducted to investigate the YAN accumulation during the final weeks of ripening. Berry samples were collected weekly from 15 vineyard sites across the Ribeira Sacra from September through harvest. Since 2009 until 2012, samples of grapes were harvested during the ripening period to study the amino acid content using HPLC-DAD techniques. Total amino acid content (TAC), total aminic nitrogen (TAN) and the yeast assimilable nitrogen (YAN) of the must samples were determined32 different amino acids of must were identified, to which we should add proline and hidroxyproline that are not assimilated by the yeasts. Proline, arginine and citrulline are the most representative amino acids in Mencía grapes. Statistical analysis found significant differences in the content of the three most abundant amino acids (proline, arginine and citrulline), according to vintages and sub-areas. The differences between the different sub-areas were also significant in the case of TAC, YAN and TAN. This work has so far confirmed that YAN level in must contributes to the terroir effect on the wine quality. YAN concentration and amino acid profile are clearly influenced by vintage and site.