Influence of cluster thinning on the amino acids concentration of musts and wines of the variety Vilana. Effect on wine volatile compounds

In this work, the influence of cluster thinning on the amino acids concentration of musts and wines was studied. Three vineyards were selected from Peza district of Crete where the white vine variety Vilana is cultivated. One part of each vineyard, containing 100 vines was divided in two sections. The first was used as reference while in the second section, cluster thinning to 50%, just before veraison, was applied. The experimentation was repeated for two continuous years. In 1996, the reference sections yielded 35.5 – 46.7 t/h while the other sections, where cluster thinning took place, yielded 16.5 – 23.0 t/h. The next year, the yields were 43.2 – 48.4 t/h and 12.6 – 14.0 t/h respectively. In all musts and wines, 18 amino acids were determined with the use of HPLC and proline was determined colorimetrically. The volatile components of the wines were also measured because, as it is known, the amino acids contribute to the formation of some higher alcohols, ethyl esters and acetates. From this work the following conclusions were made:The musts and the wines from Vilana variety are poor in amino acids and their levels vary from one year to another. This variation is related to the climatic conditions of the period of maturation but the profile of these acids seems invariable.The musts of Vilana variety deriving from vineyards with cluster thinning, which lead to low yield, contain higher levels of amino acids. This is important, given that a must rich in amino acids, positively influences not only the fermentation process evolution but also the enrichment of the wines in volatile components. Particularly for the Vilana variety, which is poor in amino acids and without any typical aroma, the high yields have a negative effect on their wine quality.