Main routes of oxygen ingress through different closures into wine bottles.

The main routes of oxygen ingress into wine bottles through "technical" cork stoppers (Neutrocork), natural cork stoppers, and synthetic closures (Nomacorc) were investigated. A comparison was made among closures left uncovered (controls), closures with the closure-glass interface covered, and closures completely covered with a polyurethane impermeable varnish. The oxygen ingress into the bottles was measured by a nondestructive colorimetric method. Technical cork stoppers were essentially impermeable to atmospheric oxygen during the first 24 months of storage. Oxygen within natural corks diffused slowly but continuously into the bottles over the first 12 months of storage and in very tiny amounts through the cork-glass interface the 12 months thereafter. Nomacorc synthetic closures were permeable to atmospheric oxygen, mainly after the first month of storage.