**Abstract**

Cork is a world-renowned material used for sealing wine bottles. Cork is a cellular material with chemical inertia and a set of physical and mechanical properties that provide an outstanding performance for in-bottle wine aging, by combining minute oxygen transfer with sealing, durability, and chemical stability, for example, inertness toward the liquid content and along storage, preventing sensory deterioration. Cork is a natural material, one of the most important nontimber forest products, that is associated with sustainability and ecosystem preservation. The cork industry has steadily improved production processes and adopted innovative technologies, quality control measures, and certification, regarding prevention of potential wine taints and off-flavors. This chapter makes a review of cork stoppers, their properties, and quality and role for wine bottle aging, tackling their importance for wine aroma and off-flavors while presenting the latest advances in cork research.

**Keywords:** cork quality, chemical composition, permeability, oxygen ingress, off-flavors, phenolic compounds
