Influence of Saccharomyces cerevisiae autochthonous strains on volatile profile of Negroamaro wine

The aim of this work is to study the influence of 30 different autochthonous Saccharomyces cerevisiae strains, isolated from Negroamaro grapes, sampled in the northern (NN strain) and in the southern (NS strain) of Salento (south Apulia, ITALY), on the volatile fraction of the corresponding Negroamaro wines made using the different isolated yeast strains by controlled microvinification processes. A further aim is to compare the volatile profiles of the as-obtained 30 different Negroamaro wines with the volatile profile of a Negroamaro wine produced by using a commercial yeast strain selected among the most employed by local producers. Modern wine makers prefer to employ commercial yeast strains due to their known specific yield and efficiency characteristics so as to ensure a reproducible product, reduce the risk of wine spoilage and allow a more predictable control of fermentation and quality. However, it's important to know the potential of using the autochthonous S. cerevisiae yeast strains with the best performance, in order to exploit them to improve wine quality and commercial standards. In the present work we have used two different analytical methods in order to analyze different compounds present in wine volatile fraction in a wide range of concentrations. Highly compounds concentrations (major volatiles) were directly determined on wine by GC-FID, whereas represented minor molecules were extracted by SPE method and then analysed by GC/MS. The complete volatile profile of all the wine samples was obtained together with a quantitative analysis by internal standardization method. Principal Component Analysis, applied to compound concentrations data showed that the wines, respectively produced with NN strains and strains NS, differentiated among them according to their aroma composition. The differences in the composition appear to be quantitative rather than qualitative. In fact, the formation of secondary products depends both on the yeast's enzymes and on the nitrogen nutrients and cofactors present in must so that the same yeast can produce different volatile patterns, depending on must composition. The obtained results suggest that the concentration of most of the volatile compounds was significantly influenced by the particular inoculated S. cerevisiae yeast strain. Autochthonous yeast strains have been shown to be able to produce wines with different volatile profiles. In particular most of NN strain have produced wines rich in alcohols and esters, most of NS strain have produced have produce wines rich in acids, esters and acetaldehyde.