## 4 Discussion  
In the course of the present study, the reduction in cork taint, mould, and \"animal\" phenolic aromas, as well as the loss of other volatile compounds such as esters, free monoterenes, and wood aromas in Austrian white and red wines, were tested using the patented filter sheet Fibrafix(r) TX in comparison with conventional sterile filter layers. Furthermore, a novel prototype of filter layers with embedded zeolites for the reduction in \"animal\" phenolic aromas was tested. The patented, commercially available filter layers were able to reduce the cork taint 2,4,6-trichloroanisole as well as geosmin, the lead substance of the mould aroma, to a sufficient extent, whereas the lead compounds of \"animal\" phenolic aromas were not reduced to a sufficient extent. The results thus not only confirm the statements of the work of [11; 12] that TCA can be reduced but also the statements of [8; 15] with regard to the positive, reducing power towards geosmin. The unconfirmed assumptions, findings from practical application, that the Fibrafix(r) TX layers filter layers can also be used to reduce strong \"animal\" phenolic taste, therefore, cannot be confirmed. The new prototype for the specific reduction in these flavours also could not substantially reach the goal of pushing the existing aromas below the perception threshold, even though these layers achieved a higher reduction (in a different trial wine) compared with the Fibrafix(r) TX layers. By filtration with the Fibrafix(r) TX, the loss of ester and monoterenes was partly considerable and very heterogeneous (from 4-90% reduction in single compounds at the beginning of filtration), but wood aroma compounds were less affected. This is in contradiction to the overall conclusion of [11], which summarises that filtration with Fibrafix(r) TX layers does not result in any significant loss of volatile compounds. However, in this study [11], only main aroma compounds, mainly higher alcohols, and carboxylic acids, were considered, but also some esters, including isoamyl acetate. With this compound, an aroma loss of about 20% was found, whereas, in the present study, the loss was 24% for this compound in the large-scale test. This means that the present study suggests another overall conclusion than [11], but looking in detail, there are some similarities between the two studies. However, there was a specific reduction in individual compounds, while other compounds were less reduced. According to the theory of zeolites acting as molecular sieves, the molecular size should be responsible for the exclusion [10]. The actual principle of elimination cannot be fully clarified. A significant correlation with the molecular weight of the compounds could not be established, although the molecular weight should tend to play a role after all. Compounds with molecular weights between 182 (geosmin) and 211 (TCA) were reduced by an average of 63.3% in the large-scale test, while compounds with molecular weights higher than 211 were reduced by only 42.6%, and compounds smaller than 182 by only 32.7%, although there were outliers declared in all three groups. The aroma loss was most significantly higher in comparison with conventional filter sheets. The fact that conventional filtration with sterile filter layers also leads to aroma loss is known from practical experience but has not been specifically studied to date. The fact that compounds such as ethyl dodecanote were reduced by up to 29% (comparison with Fibrafix(r) TX: 56%) in the large-scale test is a bit surprising. In the majority of compounds, however, the loss of volatile compounds through sterile filtration was moderate (far below 10%). A significant reduction in TCA by up to 25% by conventional depth filtration with sterilisation filter layers shows a certain potential.