# Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients
## 3 Results and Discussion
### Volatile Composition of Industrial Apple Aroma
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compound** & **Retention Time (min)** & **Concentration (mg/L) 1** & **Aroma Descriptor 2** & **Oder Threshold (ppb) 2** \\ \hline _Acids_ & & & & \\ Hexanoic acid & 42.0 & 25.4 & Sour, Fatty, Sweat, Cheese & 3000 \\ Octanoic acid & 46.5 & 5.1 & Rancid, Harsh, Sweaty & 3000 \\ _Alcohols_ & & & & \\
2-methylpropanol & 11.2 & 17.8 & Chemical & 250 \\
1-butanol & 15.6 & 548.8 & Sweet, Malty, Solventlike & 500 \\
2-Methyl-1-butanol & 19.3 & 488.8 & Highly diluted-pleasant, Malty & 300 \\
1-Pentanol & 22.1 & 30.5 & Fusel, Sweet, Fruity & 4000 \\
1-Hexanol & 27.8 & 1426.5 & Herbaceous, Green, Fruity, Slightly & 500 \\ _Cis_-3-hexenol & 28.8 & 17.9 & Grass & 70 \\ _Trans_-2-hexenol & 29.7 & 280.4 & Green, Leaf, Walnut & 400 \\ _Alddehydes_ & & & & \\ Hexanal & 10.1 & 26.5 & Green, Grass & 11 \\ _Trans_-2-hexenal & 17.8 & 111.6 & Green, Apple & 17 \\ Benzaldehyde & 33.3 & 5.3 & Bitter almond, Green almond, & 350 \\ _Esters_ & & & & \\ Ethyl-2-methylbutanoate & 8.8 & 13.6 & Sweet, Fruity, Strawberry, & 0.006 \\  & & & & Blackberry, Green apple & 66 \\ Butyl acetate & 9.7 & 59.4 & Red apple aroma & 66 \\
2-Methylbutyl acetate & 12.0 & 21.4 & Fruity & 11 \\ Hexyl acetate & 20.2 & 20.7 & Herbaceous, Fruity & 2 \\ _Phenols_ & & & & \\ Estragole & 37.3 & 1.8 & Licorice, Anise & 16 \\ \hline \hline \end{tabular}  
* Concentration expressed as pentanoic acid equivalents. 2 Odor descriptor and threshold in water, reported in the literature [13; 14; 15; 16; 17; 18; 17].  
\end{table} 
Table 2: SDE/GC-qMS volatile compound quantification of apple aroma stored at room temperature, aroma descriptors, and odor threshold reported in literature. than 1000 corresponds to compounds that have a higher impact in aroma, presenting an odor intensity in the suprathreshold area. The odor intensity is the second dimension of the sensory perception of odorants and refers to the perceived strength or magnitude of the odor sensation. Intensity increases as a function of concentration. The relation between perceived intensity and the logarithm of odor concentration is linear. The relationship between perceived intensity and stimulus concentration was described by [PERSON] as a derived logarithmic function, which is the product of the Aroma Index and Weber-Fechner coefficient (2.33), plus 0.5 [27; 28]. There is an intensity scale where 0 corresponds to \"no odor\", 1 is \"very faint odor\", 2 is \"faint odor\", 3 is \"distinct odor\", 4 is \"strong odor\", 5 is \"very strong odor\", and 6 or more correspond to \"overwhelming odor\", where the saturation is attained at 10 [26; 28]. As observed in Figure 1, each compound identified in industrial apple aroma has different magnitudes of intensity. Using the Relative Aroma Index and the HS-SPME/GC-qMS peak area data as an approach to this, there were six compounds (nonanoic acid, ethanol, benzyl acetate, 2-phenylethyl acetate, _trans_-anethole, and geranylacetone) above 1 (Table 1, Figure 1a). This allows inference that these compounds were in the subthreshold area, being irrelevant to the aroma [26]. These compounds were not identified in the industrial apple aroma analyzed by SDE/GC-qMS (Table 2, Figure 1b). The Aroma Index calculated by the concentrations estimated by SDE/GC-qMS for all compounds identified showed values higher than 1. Due to the higher detection limits of the SDE technique, the concentrations determined were in the range of mg/L, showing only the major compounds present in industrial apple aroma (Table 2). The Relative Aroma Index could be an approach to complement the contribution of a wide range of volatile compounds present in the scent of apple aroma. Comparing both values (Aroma Index and Relative Aroma Index) to the same compounds identified, it was possible to validate the semi-quantification obtained by SPME. For the family of compounds present in apple aroma, the response factors and affinity of the SPME fiber polymeric material were similar, inferring that Aroma Index is comparable to the Relative Aroma Index.