Characterization techniques comparison towards a better understanding of different cork-based stoppers types

The study aimed to evaluate the use of conventionally-applied techniques for biopolymer characterization to improve the knowledge about the properties of five different commercial cork-based stoppers types. Although low porosities were observed (max. value of 23%), for some samples the technique applied to obtain the density promoted significant changes in this property. The stoppers presented low water (WAC) and wine absorption capacities (WIAC) (max. values of 34% and 27% after 24 h, respectively), confirming cork's hydrophobicity. In general, ethanol absorption capacity was higher than WAC and WIAC. Micrographs showed that the agglomeration process used to format micro-agglomerated, silktop 1 + 1, and champagne stoppers can deform but not disrupt the cells, confirming cork's suitability to be used in stoppers' development. Besides that, agglomeration was responsible for increasing the flexibility of the stoppers, once micro-agglomerated samples presented the lowest elastic modulus (17.6 MPa); cork's thermal stability can be linked to chemical composition. • Cork is a versatile, natural, renewable, and biodegradable material. • Five different cork stoppers types had their properties evaluated. • Natural stoppers presented the lowest porosity and higher absorption capacities. • The agglomeration increased the flexibility and changed the cork's structure. • High thermal stability can be attributed to lignin presence in cork composition.