Characterisation of pinking precursors in Muscat and their dose-dependent accumulation in a Roditis skin-contact model

Abstract

Pinking in white wines occurs unpredictably due to PPO-mediated oxidation of skin-derived flavan-3-ols and hydroxycinnamic acids into quinones that form chromophores [1,2]. Conventional remedies, such as PVPP, bentonite, and SO₂, are limited by their non-selectivity, allergen concerns, and significant volume losses [3,4,5]. Although GSH can effectively trap quinones as the colourless Grape Reaction Product (GRP), its protective ability is limited, depends on concentration, and is gradually depleted during winemaking, reducing its reliability as a standalone solution [6,7,8]. The natural presence of GSH in oenological nitrogen supplements used during fermentation [9,10] indicates these preparations may provide an additional, readily available form of protection against oxidation without requiring special treatment steps. We characterised the metabolic signature of a natural pinking event in commercial Muscat (Control, Pink, Pink+P1, Pink+P2; where P1 and P2 are oenological supplements) and validated marker origins using a controlled skin-contact model in Roditis Alepou (Control; G1: 1×; G2: 2×; G3: 4× native skin w/w). All samples were analysed utilising an untargeted metabolomics approach with an HPLC-TIMS-QTOF system [11], employing Data-Dependent Acquisition (DDA) to acquire MS/MS fragmentation spectra. Among the 100 most abundant features, five were identified as pinking biomarkers: 4-Hydroxycoumarin (absent in control; +5,521 at G3), the predominant (4S,5Z,6S)-4-(2-methoxy-2-oxoethyl) derivative (Pink vs control: +36,234%; G3 vs Roditis control: +3,909%), (−)-epicatechin (+2,441%; +521%) [12,13], sinapaldehyde (+2,096%; +147%), and an unidentified compound at m/z 259.12891 (+576%; +1,977%). The monotonic accumulation from G1 to G3 confirmed their skin-derived origin [14,15]. Both P1 and P2 reduced all five markers by −9% to −32%, with the dominant precursor exhibiting the most robust response (P1: −32%; P2: −23%), in alignment with downstream GSH-mediated quinone trapping mechanisms [16,10]. The m/z 259.12891 feature is identified as the most skin-sensitive compound within the dataset. Together, these findings extend the known pinking-precursor space beyond classical flavan-3-ols and position oenological supplements as an effective, winery-compatible preventive strategy that does not necessitate additional treatment steps. Future research should aim to validate the conduct of longitudinal ageing studies to verify sustained post-bottling protection.

References

Escudero, A., Campo, E., Fariña, L., Cacho, J., & Ferreira, V. (2025). The role of polyphenols in oxygen consumption and in the accumulation of acetaldehyde and Strecker aldehydes during wine oxidation. Food Chemistry. https://doi.org/10.1016/j.foodchem.2024.142242

Bianchi, S., Bucci, M., Lisanti, M. T., & Moio, L. (2025). Accelerated oxygenation for the production of fortified (mystelle-type) sweet wines: Effects on the chemical and flavor profile. Journal of the Science of Food and Agriculture. https://doi.org/10.1002/jsfa.13978

Wang, L., Li, S., Zhang, B., Duan, C., & Shi, Y. (2025). Balancing wine stability with color and phenolic quality: Insights into the impact of fining agents and tartrate stabilization methods. Food Chemistry. https://doi.org/10.1016/j.foodchem.2025.145731

Lukić, I., Horvat, I., Zdunić, G., Carlin, S., Vrhovsek, U., & Kljusurić, J. G. (2025). Bentonite-clarified white wine: Linking clay physico-chemical properties to protein removal efficiency and wine matrix alterations. Molecules, 30(20), 4117. https://doi.org/10.3390/molecules30204117

Noviello, M., Gattullo, C. E., Faccia, M., & Gambacorta, G. (2025). Beyond color extraction: How pulsed electric fields and sulfites affect phenolic and volatile compounds of Primitivo red wine. Foods, 14(10), 1792. https://doi.org/10.3390/foods14101792

Kritzinger, E. C., Bauer, F. F., & du Toit, W. J. (2013). Role of glutathione in winemaking: A review. Journal of Agricultural and Food Chemistry, 61(2), 269–277. https://doi.org/10.1021/jf303665z

Giménez, P., Just-Borras, A., Pons, P., Gombau, J., Heras, JM., Sieczkowski, N., Canals, JM. & Zamora, F. (2023). Biotechnological tools for reducing the use of sulfur dioxide in white grape must and preventing enzymatic browning: Glutathione; inactivated dry yeasts rich in glutathione; and bioprotection with Metschnikowia pulcherrima. European Food Research and Technology, 249, 1491–1501. https://doi.org/10.1007/s00217-023-04229-6

Viola, E., Naselli, V., Prestianni, R., Matraxia, M., Pirrone, A., Craparo, V., Vagnoli, P., & Alfonzo, A. (2024). The use of a specific glutathione-rich inactivated yeast to protect organic Catarratto grape must and wine from oxidation in the pre-fermentative phase. Food Bioscience, 61, 104656. https://doi.org/10.1016/j.fbio.2024.104656

Garcia, R., Soares, B., Dias, C. B., & Freitas, A. M. C. (2025). White wine lees as a source of antioxidants: Insights into their chemical composition and bioactive potential. Food Chemistry. https://doi.org/10.1016/j.foodchem.2025.146118

De Iseppi, A., Lomolino, G., Marangon, M., & Curioni, A. (2024). Chemical and electrochemical assessment of wine lees extracts tested as novel antioxidant additives in model wine. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.3c00567

Arapitsas, P., Marinaki, M., Virgiliou, C., & Theodoridis, G. (2026). Untargeted metabolomics reveals key biochemical shifts during industrial Muscat of Alexandria alcoholic fermentation. Food Chemistry, 506, 148090. https://doi.org/10.1016/j.foodchem.2026.148090

Singleton, V. L. (1987). Oxygen with phenols and related reactions in musts, wines, and model systems. American Journal of Enology and Viticulture, 38(1), 69–77.

Cheynier, V., Duenas-Paton, M., Salas, E., Maury, C., Souquet, J. M., Sarni-Manchado, P., & Fulcrand, H. (2000). Structure and properties of wine pigments and tannins. American Journal of Enology and Viticulture, 57(3), 298–305.

Dursun, A., Ağçam, E., & Akyildiz, A. (2025). Effect of maceration time and fermentation technique on the phenolic composition and color of wines. Anais da Academia Brasileira de Ciências, 97(1). https://doi.org/10.1590/0001-3765202520241467

Tu, M., Sun, X., Wang, J., Chen, W., & Li, H. (2025). Effects of varying proportions of grape skins, seeds, and stems added prior to fermentation on the phenolic composition and sensory characteristics of wine. Food Chemistry. https://doi.org/10.1016/j.foodchem.2025.145628

Parnigoni, M., Fracassetti, D., Tirelli, A., & De Iseppi, A. (2025). Effect of contrasting redox potential evolutions and cap management techniques on the chemical composition of red wine. Molecules, 30(15), 3172. https://doi.org/10.3390/molecules30153172