Corks are the traditional closures for wine bottles and jars, cut from the bark of the cork oak. Their natural compressibility creates a tight seal while their cellular structure resists liquid absorption, allowing controlled oxygen transmission that benefits wine maturation. However, microbial growth on corks can cause the sensory defect known as corking, and corks risk releasing 2,4,6-trichloroanisole, tannins, or peroxides into the wine. These drawbacks have driven the development of synthetic plastic closures as alternatives, though natural cork remains prized for premium wines when sourced from quality-controlled suppliers.