Novel ATR-FTIR and UV-Vis spectral markers for assessing the Prooxidant/Antioxidant Balance (PAB) in white wines

The browning index (BI), based on the absorbance at 420 nm, is a common oxidation marker in white wines, typically measured after thermal stress (50–60 °C for 5 up to 12 days) in air-saturated wines. However, oxidative shifts begin much earlier, with initiation and propagation reactions altering the prooxidant/antioxidant balance (PAB) before browning appears. This study investigates whether non-targeted fingerprinting by ATR- FTIR and UV-Vis spectroscopy can capture early-stage compositional changes that occur during the first hours of the treatment (1 – 8 hours at 60 °C). Moschofilero wines (2023 vintage, two bottling batches) were used for this purpose. Spectral data were analyzed using Principal Component Analysis (PCA) and Generalized Two- Dimensional Correlation Spectroscopy (2D-COS). Key oenological and antioxidant-related parameters (free and total SO₂, pH, redox potential, total phenols, DPPH•, FRAP) were also monitored. Time-related patterns of UV- Vis absorbance at 350–370 nm, possibly linked to Fe(III)-tartrate complexes and ATR-FTIR shifts at 3000–3600 cm⁻¹, due to hydrogen bond rearrangements, were observed. They coincided with a rise in redox potential (+106 to +123 mV) and free SO₂ depletion (below 30 mg/L), indicating a progressive decline of wine redox buffering capacity. In contrast, the total phenolic content and antioxidant activity remained unchanged. Validation with additional samples (Asirtiko, Malagouzia, vintages 2022, 2023) confirmed the potential of the identified markers. These findings highlight a novel approach for interpreting UV-Vis and ATR-FTIR spectroscopic data to monitor early oxidation in white wines. Further validation is ongoing to support the development of rapid, non- destructive, and data-driven tools for proactive wine stability management and more sustainable oenological practices.