Untargeted metabolomics to investigate the phenolic composition of Chardonnay wines from different origins

Chardonnay is a grape variety widely used to produce different white wine styles. In this work, a metabolomic approach based on ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-ESI/QTOF-MS) has been applied to clarify the entire phenolic composition of commercial Chardonnay wines. For this purpose, six wines from different viticultural regions were comprehensively profiled and the phenolic markers discriminating different samples were identified through orthogonal partial least squares discriminant analysis (OPLS-DA). Polyphenols were quantified according to their chemical class and subclass. The most abundant phenolic compounds detected in Chardonnay wines were campesteryl ferulate, caffeic acid and 4-hydroxybenzoic acid (on average 42.4, 5.7, and 5.6 mg/L, respectively). The averaged stilbenes' content detected (as resveratrol equivalents) was 1.3 mg/L. Flavonoids (i.e., flavonols) were the main class of polyphenols contributing to discrimination of wines according to their geographical origin. Furthermore, the OPLS-DA approach provided an excellent discrimination when considering steel vs. barrel ageing process. These preliminary findings highlight that UHPLC-ESI/QTOF MS-based profiling appears to be a very promising approach in the comprehensive analysis of nutraceuticals, such as polyphenols, in white wine from different geographical origin.