Analysis of mechanical properties of cork stoppers and synthetic closures used for wine bottling

There is an increasing interest towards synthetic closures as an alternative to cork stoppers for sealing wine bottles. In this preliminary study, a set of testing conditions using the TA-HDI Texture Analyzer were implemented to measure selected mechanical parameters for the characterization of wine closures (natural and technical corks, co-extruded and injected synthetic closures in terms of compression force, extraction force and resilience. The results showed the presence of significant differences among the closures for the parameters tested. Injected closures were characterized by the highest weight (range = 6.8–7.2 g), whereas the corks showed wide variability (SD = 0.23–0.57 = 4.4–15.3%). The force required to pull-out the closure from the bottle ranged between 176 and 421 N and the extreme values were found on natural (196 ± 20 N) and technical cork (329 ± 39 N). The force of compression was highest for corks (1006–1046 N), whereas lowest values were found for the synthetic closures (566–639 N). The Principal Component Analysis grouped the synthetic closures according to the technology process, i.e. injected and co-extruded, whereas the corks broadened aside with a little dispersion of technical cork compared to the natural cork.