Unraveling Vitis vinifera L. grape maturity markers based on integration of terpenic pattern and chemometric methods

The current research attempts to provide an alternative tool for grape maturity measurement related to the wine composition since, the classical parameters (weight grape berries, sugar content, titratable acidity), commonly used in the winemaking industry, do not provide any sensorial information. In this context, the evolution of terpenic compounds (TC) during ripening of four V. vinifera L. grape varieties - Bual, Malvasia, Sercial (white grapes) and Tinta Negra (red grapes), was investigated, in addition to the establishment of terpenic pattern, using headspace solid phase microextraction (HS-SPME) combined with GC–MS. Using the optimal analytical conditions were identified 62 TC in the investigated V. vinifera L. grapes. The integration of chromatographic and chemometric data provides a powerful strategy to identify potential maturity markers. The maximum potential of mono- and sesquiterpenic compounds was reached at maturity, whereas the highest levels of norisoprenoids were observed at véraison. Partial Least Squares Regression (PLS-R) was employed to describe the relationship between classical parameters and TC. Based on PLS-R models, three monoterpenic (linalool, α-terpineol, carvomenthol), one sesquiterpenic (bicyclogermacrene) and two norisoprenoids compounds (vitispirane I, β-damascenone) could be used to define the optimum harvest date. The obtained results represent a very important tool to support, in an objective way, the winemakers decision for long-term strategic planning based on the sensory potentialities of grape varieties and consequently improving the excellence of Madeira wine.