Cork and Cork Stoppers: Quality and Performance

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.

Bottle Aging and Storage of Wines: A Review

“…To avoid the spoilage caused by these compounds, preventive measures to avoid contamination must be taken during the winemaking process, as well as a proper storage of the bottles in a likewise sanitized environment [ 169 , 170 ]. Nevertheless, sanitizers used must be free of chlorine, since this chemical might bind with cork components to form TCA and TBA [ 171 ]. An alternative way to partially avoid the appearance of the responsible microorganisms is using synthetic stoppers or screw caps, since are easily sterilized and do not promote the growth of the microorganism responsible for these compounds.…”

Cork Development: What Lies Within

“…Regardless, all cork removed from the tree can be exploited commercially as raw material for final products as agglomerates. Only second reproduction cork and following harvests named “amadia” cork meets the quality standards necessary for stopper production demanded by wine companies [ 11 ] ( Figure 1 b). Stopper bottles are the product with the higher industrial revenue; however, the amount of available good-quality cork needed is becoming scarcer in the field, compromising cork manufacturing goals.…”

“…Albeit, the importance of cork products in countries like Portugal, which accounts for 2% of all exported goods, cork production has shown a reduction of 2.7% over the last decade [ 11 , 12 ] reflecting a cork oak decline associated with abiotic stresses phenomena such as prolonged drought events and ever more frequent and long-lasting heat waves [ 14 ]. These authors came to the conclusion that besides environment, tree genetics have a strong contribution to the cork chemical composition.…”

Cork, a Natural Choice to Wine?

“… Schematic representation of the cellular structure of cork with scanning electron micrographs of sections of reproduction cork: ( a ) tangential, ( b ) radial, and ( c ) transverse sections, from [ 14 ]. …”

“…Ultimately, such research would be crucial to obtaining a predictive tool to improve wine production and quality [ 9 ]. Several reviews have already focused on the wine’s evolution and the main characteristics of cork [ 9 , 10 , 11 , 12 , 13 , 14 ]. However, none of them showed the correlation that may exist between the wine ageing under a natural cork stopper and the compounds that can be extracted from cork.…”