Zeolites: A selective alternative for managing volatile phenols in wine

Abstract

The wine industry is undergoing profound changes. Climate change, evolving pest pressure, and shifting oenological practices – notably the reduction of SO₂ and increasing pH levels – are creating an environment conducive to the emergence of contaminating molecules and organoleptic defects. While current winemaking tools can treat some of these deviations, they often lack specificity, impacting the structure or aromatic profile of the wine. In response to the demand for environmentally friendly processes, zeolites offer innovative prospects. These crystalline aluminosilicates, already authorized by the OIV for TCA removal, possess adjustable porosity and modulable physicochemical properties that enable high-precision adsorption. Recent works have validated their effectiveness in reducing pesticide residues (patented results). Current research is diversifying targets toward the mitigation of heavy metals and molecules responsible for premature oxidation or volatile phenol spoilage. This study focuses on the adsorption capacity of various zeolite structures regarding phenolic ring molecules, such as ethyl phenols (4-EP, 4-EG) derived from Brettanomyces bruxellensis and molecules from wildfire smoke. Adsorption kinetics and isotherms of 4-EP and 4-EG were determined in model solutions, including competition tests and studies on medium complexity. The performance of the best-performing zeolites was assessed on numerous wines and compared to classical adsorbers like activated carbons. The study showed that specific zeolites could adsorb large quantities of volatile phenols. This effectiveness is linked to zeolite topology, chemical composition, and concentration. Furthermore, unlike activated carbon—which has high gross efficiency but is non-specific—zeolite preserves the integrity of the wine. While carbon causes a loss of color and aromatic complexity, zeolite treatment maintains analytical and sensory balance. These results confirm the significant superiority of selected zeolites for the adsorption of target compounds. Selecting the right zeolite can drastically reduce volatile phenol levels without the drawbacks associated with activated carbons. This work highlights the importance of understanding adsorption mechanisms and molecular selectivity to adapt the material to the specific winemaking challenge.

References

Noviello, M.; Gattullo, C.E.; Faccia, M.; Paradiso, V.M.; Gambacorta, G. (2021).  Application of natural and synthetic zeolites in the oenological field. Food Res. Int., Volume 150, Part A