Impact of the deposition process on oxygen barrier properties of wine bottle overcapping waxes

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This study investigates how processing conditions, particularly temperature, affect wax adhesion on glass wine bottlenecks and the related long-term barrier properties of the sealing system. First, the surface properties of both glass and liquid wax were characterized at temperatures corresponding to the classical coating process conditions. While the total surface tension of glass (25°C to 70°C) and wax (100°C to 120°C) remained stable, the balance between polar and dispersive components shifted slightly with temperature, with the dispersive component becoming predominant at higher temperatures. Second, extraction force tests and oxygen permeability measurements revealed that the temperature of the bottleneck during wax application critically determines the final barrier performance. When wax was deposited on glass heated between 25°C and 50°C, oxygen transfer was highly heterogeneous, with OTR values ranging from low (<0.1 mg·year⁻¹) to very high (>30 mg·year⁻¹). This also correlated with weaker extraction forces from the wax to the bottleneck, around 50 N. However, applying wax to bottlenecks preheated to temperatures between 60°C and 70°C consistently led to stronger adhesion, evidenced by higher extraction forces and low, homogeneous OTR values (<0.1 mg·year⁻¹), similar to the intrinsic barrier properties of the wax. These results demonstrate that higher bottleneck temperatures (>60°C) during wax application improve adhesion between wax and glass and effectively limit oxygen ingress through the wax–glass interface. Overall, this work identifies bottleneck preheating as a critical processing parameter that governs wax adhesion and, in turn, long-term oxygen protection.

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