# Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients
## 3 Results and Discussion
### Volatile Composition of Dried Apple Pomace and Its Infusions  
After conventional hot-air drying at 80 \({}^{\circ}\)C, the apple pomace was stabilized and the volatile composition of the dried sample was analyzed by HS-SPME/GC-MS. The composition of the headspace revealed the presence of 15 compounds (Figure 5). Those present with high intensity were hexanol, 2-ethyl-1-hexanol, hexanal, furfurral, benzenemethanol, benzothiazazole, and 2-methoxy-6-methylpyrazine, with odor descriptors associated to green notes, toasted, caramel, and sweet [17; 35; 40].  
Figure 4: Heatmap comparing the apple hydrodistillate obtained from the wet apple pomace (from January 2014 production) and apple aroma obtained from the industrial juice processing, also from January 2014 production. Columns correspond to duplicates of each sample analyzed by HS–SPME/GC–MS. The GC peak area intensity was represented in a blue to red scale, normalized between the minimum and maximum areas for each compound. Table S1 shows the identification of the volatile compounds present.  
As strategy of valorization, the dried apple pomace performance as an infusion ingredient was also evaluated. Taking in account the consumer preferences when the infusion is tasted, the volatile compounds were determined with and without sugar addition. The volatile profile of the infusions prepared with dried apple pomace allowed the identification of 35 volatile compounds in both infusions (Figure 5), a much higher number than those identified in the dried apple pomace. The infusions prepared without added sugar showed a presence of more intense peaks, namely from the chemical families of aldehydes, esters, and intergenic compounds. From these, 29 were associated with positive notes to the aroma, 20 of them with notes of fruits, apple-like, citric, and spicy. Five compounds were associated with notes of mushroom, fatty, and cucumber, usually depreciated.  
The infusion with sugar addition showed a less intense volatile profile in most of the compounds present. The exception is the benzaldehyde that showed a higher intensity, possibly contributing to almond, caramel, and sweet notes to the infusion [40]. The sugar ability to modulate the aroma perception of the infusion has been reported for sucrose syrups with high \({}^{\circ}\)Brix [41]. The increase of sucrose concentration has been reported to decrease the flavor perception of hexanal and _trans_-2-hexenal, the green notes, while increasing the fruity notes [41]. In filtered aqueous matrices, the effect of sugar addition tends to increase the headspace partitioning of volatile compounds [42] resulting from a \"salting out\" effect. This relative volatility of the flavor compounds in aqueous solutions increases with their hydrophobicity [43]. In the apple infusions with sugar addition only, benzaldehyde was enriched in the headspace, which cannot be explained by its hydrophobicity [43]. It is possible that the generation of benzaldehyde during  
Figure 5: Heatmap of the volatile composition of the dried apple pomace at 80 \({}^{\circ}\)C and infusions obtained with dried apple pomace (from January 2014 production) without and with sugar addition. Columns correspond to triplicates of each sample analyzed by HS–SPME/GC–MS. The GC peak area intensity is represented in a blue to red scale normalized between the minimum to maximum areas for each compound.  
brew preparation could arise from Strecker degradation of phenylalanine in the presence of sugars [44]. All other volatile compounds tend to decrease with the sugar addition, probably due to the presence of apple pomace matrix in the brew, a phenomenon also observed in pulp juices [45]. This phenomenon was only visible in the presence of sucrose because this sugar acts as a solvent sequesterator, which, together with the release of pectin through the cell wall matrix, increases the viscosity of the solution, preventing volatile compound diffusion to the headspace, possibly tending to be sorbed to the apple pomace hydrophobic matrix.