## 3 Results and Discussion
### Investigation of the Apple Wines
#### 3.2.3 Sensory Analysis  
In addition to the analysis of non-volatile and volatile compounds, we aimed to investigate the impact of different fermentation strategies on the sensory properties of the resulting _Ilzer Rose_ apple wines. As we were not interested in the appeal of the products to consumers, but in a detailed sensory characterization of the products, we worked with a well-trained panel. Due to the well-known limitations of sensory techniques that are based on intensity scoring, we decided to apply CATA which is a citation frequency-based method. The suitability of CATA for product characterization with the use of trained panellists has been described in the literature previously [37; 38]. The selection of appropriate descriptors is regarded as essential. Descriptors were collected from the panellists during the pre-study and training phase. The final list of descriptors contained no attributes referring to liking or preference and consisted solely of strictly analytic descriptors that were considered as important for apple juices and apple wines. Prior to the statistical analysis, one attribute (\"exotic\") was removed from the list as it was not ticked in any individual protocol. Figure 5 shows the results of the sensory evaluation in terms of a biplot after correspondence analysis. As from the multivariate analysis of the volatile compounds (Figure 4), a clear differentiation of the apple wines was obtained by CATA analysis. The attributes with the highest significance and thus, the highest impact on the classification of the apple wines, were the attributes 'apple flavour', 'high acidity', 'inexpressive/bland', 'yeast notes', 'apple skin', 'fermentative notes' and 'woody'. All other descriptors were not discriminative, but they nevertheless deliver valuable information about the products. Similar product groupings were obtained as from the analysis of the volatile compounds (Figure 4). The product AW1 did not show correlations with any of the other apple wines; AW1 showed high correlations with the descriptors 'inexpressive/bland', but also with the positively associated descriptors 'complex fruits' and 'wine-like'. As from the results of the volatilome, high correlations--and thus high similarities in flavour--were observed between AW2 and AW4 as well as between AW3 and AW5. The results from sensory evaluation again demonstrate that the addition of the clarifying agent Gerbinol(r) does not significantly impact the flavour, but that the fermentation strategy (i.e., maccation of the mash and mash fermentation) is the driver for the formation of distinct flavour properties. The maceration of the mash prior to the controlled fermentation of AW2 and AW4 leads to the promotion of 'apple flavour' in the wine supported by 'green/grassy', 'citrus' and 'floral' notes. In addition, AW2 and AW4 are strongly correlated with the term 'high acidity' which is in accordance with the higher concentrations of acids in these products (Table 2). The biplot in Figure 4 shows a strong correlation of AW2 and AW4 with a large number of fruit esters--their presence seems to be responsible for the expressed perceived fruitiness of AW2 and AW4. The apple wines AW3 and AW5 are strongly correlated with the descriptors 'fermentation' and 'yeast notes', 'woody' and 'apple skin'. Furthermore, descriptors such as 'oxidative note' or 'dry fruits' show high correlations with the mash fermented products. In a recent study, the impact of the amount of grape skin during white wine fermentation on the sensory properties of the resulting products was investigated. A similar behaviour--loss in fruitiness and floral notes, loss in acidity, increase in sensory properties not related to fresh fruitiness--was observed in this study [24]. The observed malo alncatic fermentation in AW3 and AW5 is the reason for perceived low acidity of these two fruit wines.  
Figure 4: PCA plot (Pearson correlation) showing the correlation of the volatile compounds and the apple wine samples.