Influence of two yeast strains and different nitrogen nutrition on the aromatic compounds in Lugana wine

Abstract

Lugana Protected Designation of Origin (PDO) wines are made from Turbiana grapes. The aroma of Lugana wines results from the combined contribution of esters, terpenes, norisprenoids, sulfur compounds and the benzenoid methyl salicylate. This study aims to investigate how volatile aroma compounds are affected by different nitrogen supplies and yeast strains. Wines were produced with a standard protocol with 2021 Turbiana grapes with two different yeasts Zymaflore Delta e Zymaflore X5 (Laffort, France). During the alcoholic fermentation of the must when H2S appeared additions of various nitrogen supply were made: inorganic nitrogen, organic nitrogen, a mix of inorganic and organic nitrogen and organic nitrogen with an addition of pure methionine. Free volatile compounds were analyzed using GC-MS techniques. Analyses during the alcoholic fermentation process of the Lugana wines indicate that Zymaflore Delta developed higher concentrations of H2S than the other. Instead observing the influence of the different nitrogen nutrients it can be said that the best solution to limit the formation of H2S is to use the mix of organic and inorganic nitrogen. For almost all the biochemical classes of the analysed compounds, a statistically significant difference was shown about the yeast variable. Regarding the differences given by the variable of nitrogen nutrition, however, it is shown that all classes are influenced by it. With regard to Lugana wines fermented with Zymaflore Delta, the addition of the mix of organic and inorganic nitrogen led to higher concentrations of α-terpineol, the use of organic nitrogen favored a higher presence of TDN, and the use of this type of nitrogen added with methionine led to higher concentrations of α-terpineol. On the other hand, wines fermented with Zymaflore X5, the addition of the nitrogen nutrition mix during fermentation resulted in higher concentrations of norisoprenoids, while the addition of organic nitrogen and methionine resulted in higher levels of DMS, linalool, α-terpineol and methyl salicylate. This study showed that the choice of yeast proved to be the variable with the greatest impact on the volatile chemical profile of the wines studied. Furthermore, the choice of nitrogen nutrient had a significant impact on the production of volatile compounds but did not follow a specific trend within the classes of compounds that could be defined as improving or worsening the general aromatic profile of the wines.