Exploring the chemical space of white wine antioxidant capacity: A combined DPPH, EPR and FT-ICR-MS study

•Classification of 106 white wines by high, medium, or low antioxidant capacity.•Isolation of 365 molecular markers correlated with high antioxidant capacity.•Putative identification of oxidative reaction products.•Elucidation of the importance of CHONS and CHOS compounds in the antioxidant metabolome of dry white wines.•Proposed chemical mechanism explaining differences between DPPH and EPR measurements. The chemical composition and functionality of molecular fractions associated with dry white wines oxidative stability remain poorly understood. In the present study, DPPH assay, electron paramagnetic resonance spectroscopy (EPR) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were used to explore the chemical diversity associated with the antioxidant capacity (AC) of white wines. AC determined using the DPPH assay and EPR were complementary and enabled differentiation of wine samples into groups with low, medium, and high AC. Mass spectra variations associated with global DPPH- and EPR-derived indices enabled identification of 365 molecular markers correlated with samples with high AC, of which 32% were CHO compounds including phenolic and sugar derivatives, 20% were CHOS and 36% were CHONS compounds including cysteine-containing peptides. This study confirmed the importance of CHONS and CHOS compounds in the antioxidant metabolome of dry white wines. Knowledge about these compounds will enable better understanding of the oxidative stability of white wines and therefore aid in achieving optimum shelf life.