Development of two-level design of experiments for the optimization of a HS-SPME-GC-MS method to study Greek monovarietal PDO and PGI wines

Aroma is a key element in the description of wine's hedonistic character and commercial value. The volatile compounds that compose a wine's aroma belong to various very different chemical groups and their concentration varies from ppt to ppm. Therefore, the development of an analytical method able to cover such variability is a challenging task. In the present work, arduous method development was applied to reach optimal headspace solid-phase microextraction (HS-SPME) conditions, for the characterization of wine volatilome, by using a two-level screening-to-modelling Design of Experiments (DoE) approach. The optimized and comprehensive HS-SPME-GC-MS protocol was then used for the analysis of seventy wine samples of six monovarietal Greek Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI) white and red wine cultivars (Moschofilero, Assyrtiko, Savvatiano, Malagouzia, Agiorgitiko and Xinomavro). One hundred volatile metabolites were identified and semi-quantified in several concentration ranges according to variety. Fatty acids and their corresponding ethyl esters were found in higher concentrations in the white wines, while higher alcohols were characteristic for the red wines. Differences between the cultivars were evaluated through multivariate statistical analysis and PCA and OPLS-DA models. The results demonstrated that Moschofilero is a very aromatic and floral variety, as it is very rich in terpenic compounds, while Malagouzia and Agiorgitiko were characterized by isoamyl alcohol and ho-trienol, respectively