Creating cleaner, taint-free natural corks

New technologies developed by Amorim guaranties TCA free cork stoppers

By Paulo Lopes* and Miguel Cabral*

Figure 1. Naturity® technology which removes TCA and hundreds of other volatile compounds by thermal desorption through a proprietary, nonsequential use of pressure, temperature, purified water and time.

Throughout the years Amorim Cork has been leading the technological development on cleansing technologies designed to eradicate compounds that can be responsible for the cork taint. Amorim Cork was the first company to develop in 2003 an industrial superheated steam cleaning process, called ROSA® (Cabral 2005), to remove TCA from cork granules, which was independently validated by AWRI and Campden BRI (Hall et al. 2004; Sefton and Simpson 2005). The first version of the ROSA system was able to remove 75 to 80% of the released TCA from cork granules. Over the years, Amorim was able to upgrade and optimize the ROSA (ROSA Hightech) to yield 100% of TCA remove when the levels of releasable TCA in granules were lower than 6 ng/L. In 2005, the ROSA process was upgraded, and applied to the treatment of natural cork stoppers (ROSA Evolution®), removing by 80 to 85% its TCA levels. Bottling trials have fully demonstrated the effectiveness of the ROSA® and ROSA Evolution®, processes to remove the TCA from cork and therefore prevent its transfer into wine over the years. The extraction of haloanisoles with steam has become one of the most typical processes, with numerous variants having been proposed by the different cork manufacturers.

More recently, Amorim Cork launched Naturity®, a new technology to remove TCA and other compounds with similar properties, from natural cork stoppers by thermal desorption (Figure 1). The level of TCA extraction can be as high as 99%. Removal is based on desorption stimulated by temperature which supplies thermal energy to break the bond between the volatile contaminants and cork, in a process that can be described as thermal vaporization assisted by vacuum (Teodoro 2018). Others proposed similar processes but comprising preliminary stages of recrystallisation of haloanisoles that precedes the desorption stage, which allegedly enhances the removal of contaminants (Palacios et al. 2013). To guarantee that the haloanisoles and halophenols are in a gaseous state, the desorption stage must take place at a temperature higher than the boiling temperature of contaminant compounds, which depend on the pressure applied to the cork. The melting and boiling points of contaminant compounds quickly decrease when the pressure diminishes. For example, TCA at a pressure of 1 mbar it would require 56°C; at 10 mbar 98°C and at 1000 mbar 239°C. Thus, the thermal removal of TCA and other contaminants can be performed at very moderate temperatures, if very low pressures are used.

Amorim also developed NDtech® in collaboration with a UK Company, a process for the high-end natural corks, where each individual cork stopper is analyzed for TCA, by gas chromatography in a high-speed industrial process (Figure 2). With this system, high-end natural corks have an additional guarantee for TCA.

Taylor et al. (2000) used supercritical fluid extraction of cork stoppers in a new analytical method to determine TCA in corks. This technique was evolved into an industrial process to remove TCA from cork granules (Lumia 2001). This process comprises the circulation of supercritical CO₂ fluid (100-300 bar) at a certain temperature (40-80°C), with water as co-solvent through a batch of cork granules. Contaminant compounds from cork are extracted by solubilizing in the CO₂ fluid which then is purified in a separator and an adsorbent. This process is very effective to remove TCA (eliminate 100% of the TCA content when the levels of releasable TCA in granules (0.3 to 1.4 mm) are up to 18 ng/L) from cork granules (Lumia and Aracil 2006); however, it is time and energy consuming. In 2021, Amorim Cork developed, Xpür, a new generation of industrial CO₂ supercritical equipment’s, by reengineering and upgrading the concept developed several decades ago (Figure 3). Amorim’s Xpür removes of 100% of contaminants such as TCA from cork granules with different dimensions regardless the initial content levels of releasable TCA using only 25% of the energy and 10% of the CO₂ previously required by the more conventional technologies.

 

The extraction of haloanisoles with steam has become one of the most typical processes, with numerous variants having been proposed by the different cork manufacturers.

 

References

Barker, D.A.; Capone, D.L.; Pollnitz, A.P.; McLean, H.J.; Francis, I.L.; Oakey, H.; Sefton, M. 2001. Absorption of 2,4,6-trichloroanisole by wine corks via vapour phase in an enclosed environment. Australian Journal of Grape and Wine Research 7, 40-46.

Cabral, M. 2005. Cork product treatment process by extraction of compounds dragged in water vapour. Patent no EP1551463A1.

Hall, M., Byrd, N.; Williams, J. (2004). An assessment of the effect of the ROSA treatment on the levels of TCA natural contaminated cork granules. Australian and New Zealand Grapegrower and Winemaker 484, 57-59.

Lumia G; Perre, C.; Aracil, J.M: 2001. Method for treating cork for extracting organic compounds with a dense fluid under pressure. Patent No WO 2001023155.

Lumia G; Aracil, J.M: 2006. Supercritical fluids – An innovation for cork closures. Revue des Oenologues 118, 1-4.

Palacios, F.S.; Misiego, C.; Montero, M.J.; Garcia, J.; Sánchez, N. 2013. Process for the elimination of the haloanisoles and halophenols present in cork and installation. Patent no EP 2 639 025 B1.

Sefton, M.; Simpson, R. 2005. Compounds causing cork taint and the factors affecting their transfer from natural cork closures to wine – a review. Australian Journal of Grape and Wine Research 11, 226-240.

Taylor, M.K.; Young, T.M.; Butzke, C.E.; Ebeler, S. 2000. Supercritical fluid extractionof 2,4,6 – trichloroanisole from cork stoppers. Journal of Agricultural and Food Chemistry 48, 2208-2221.

Teodoro, O. 2018. Processo de extração de contaminantes voláteis da cortiça por dessorção térmica. PT 109878 A.

 

*Amorim Cork – R. dos Corticeiros, 850, 4535-387 Santa Maria de Lamas – Portugal