Steam has long been known to be effective in the laboratory for removing volatile compounds such as 2,4,6-trichloroanisole (TCA) from cork. However, getting the process to work reliably on an industrial scale has, before now, eluded cork manufacters.

In scaling up its laboratory trials of ROSA to an industrial system, Amorim's researchers and engineers have had to overcome many obstacles, including:

• uneven levels of reduction of TCA
• adverse effect of the process on the cork's physical properties and visual appearance
• recontamination of the cork due to steam condensation.

The research team found that steam treatment may deform a finished cork, which requires costly and time-consuming rectification, and that steam at high temperatures – while more effective at removing TCA – will adversely affect proportionally more corks than steam at a lower temperature.

This necessitated a series of trials to establish the optimal balance between TCA removal and level of deformation, a research effort that is continuing.

As at 2003, the ROSA process has been perfected for cork granules, which are used in the manufacture of technical corks. A major R&D effort is continuing into optimising the process for whole cork stoppers.

Validation of the process

Amorim's own internal validation of the process has shown that ROSA is highly effective in reducing the concentration of releasable TCA in natural cork. The internal test also revealed that ROSA has little impact on the physical properties of the cork granules.

In addition to its own research, Amorim commissioned independent validations of ROSA by suitably-accredited laboratories – the Australian Wine Research Institute (AWRI), Campden & Chorleywood Food Research Association (CCFRA) in the UK and the Geisenheim Research Institute in Germany.

These respected laboratories undertook chemical analytical tests on cork samples before and after treatment with ROSA to determine the average level of reduction in releasable TCA.

In each case, half the samples were analysed in Portugal using the Amorim laboratory facilities; the other half were analysed in the researchers' own laboratories.

The test results from each laboratory were highly consistent and extremely encouraging. They indicate very large reductions (69-80 per cent) in the average level of TCA in the cork material and provide strong evidence that ROSA is an effective industrial treatment for TCA-affected wine corks.

These results corroborate those of Amorim's own internal validation trials and, as a result, Amorim is introducing the ROSA system into the treatment of cork granules in all its technical cork plants in Portugal.

Amorim is continuing to develop the ROSA process for natural cork stoppers and technical corks. Internal validation has shown comparable reductions in TCA levels for the process in these products at a semi-industrial scale.

Bottling experiments