## 3 Results and Discussion
### Profile of Volatile Compounds  
A total of twenty-eight volatile molecules were identified in fresh apple juice (Table 3). These compounds recognized were similar to those found in other studies for different apple juice \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Fresh Apple Juice** & \multicolumn{4}{c}{**Cryoconcentration**} \\ \cline{3-5}  & & **Cycle 1** & **Cycle 2** & **Cycle 3** \\ \hline _Bioactive compound content_ & & & & \\ TPC (mg GAE/100 g d.m.) & 244.3 \(\pm\) 17.04  & 364.8 \(\pm\) 29.05  & 606.3 \(\pm\) 41.95  & 818.9 \(\pm\) 33.04  \\ TPC retention, \% & - & 66.1 & 77.2 & 84.9 \\ TFC (mg CEO/100 g d.m.) & 81.5 \(\pm\) 12.24  & 115.6 \(\pm\) 4.55  & 185.5 \(\pm\) 13.12  \\ TFC retention, \% & - & 62.8 & 70.8 & 77.0 \\ TFLC (mg CEO/100 g d.m.) & 123.8 \(\pm\) 6.14  & 169.8 \(\pm\) 10.05  & 255.1 \(\pm\) 16.32  & 344.9 \(\pm\) 20.04  \\ TFLC retention, \% & - & 60.7 & 64.1 & 70.5 \\ _Antioxidant activity_ & & & & \\ DPPH (\(\upmu\)mol TE/100 g d.m.) & 522.5 \(\pm\) 44.94  & 1039.6 \(\pm\) 43.45  & 1315.7 \(\pm\) 14.55  & 1803.2 \(\pm\) 25.55  \\ FRAP (\(\upmu\)mol TE/100 g d.m.) & 467.1 \(\pm\) 27.24  & 1277.4 \(\pm\) 121.55  & 1635.8 \(\pm\) 78.4  & 2935.5 \(\pm\) 198.3  \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Bioactive compounds content and TBC retention (%) of fresh juice and cryoconcentrate samples at each cycle1. varieties [42; 43; 44], which indicates that several factors affect the production and amount of volatile compounds in a fruit juice, such as harvest, juice extraction, and/or industrial steps, among others. The fresh juice presented fourteen esters, eight alcohols, four aldehydes and two ketones. Specifically, four esters (propanoate, 3-methylbutyl acetate, 2-methyl butyl acetate, ethyl pentanoate) exhibited higher concentration than other compounds (Figure 4). These results corroborate that esters are the main volatile compounds in apple that contribute to its characteristic fruity aroma [45]. In addition, in both fresh juice and cryoconcentrated samples, sixteen volatile molecules are unknown since no reliable matching was performed with previous studies. A lower amount of volatile compounds in the all cycles than fresh juice was detected after CBCC, which can be attributed to the volatilization of components through repeated freezing and thawing operations (Figure S1, see Supplemental Materials). However, as cycles progressed, the aromatic profile was increased, with 18, 22, and 29 compounds in the first, second, and third cycle, respectively. The increase in volatile components could be due to the high concentration of each component (reflected in TSSC) cycle-by-cycle, which can be detected by the chromatograph. This effect is consistent with observed by [PERSON] et al. [46] in coffee beverages, indicating that the concentration of sugars (such as sucrose, glucose, and fructose) positively affects the release of volatiles in the headspace. The volatile compounds concentrated by BCC are showed in the chromatograms. These results were consistent with those found by [PERSON] et al. [27], [PERSON] et al. [47], [PERSON] et al. [48], and [PERSON] et al. [49] for coffee extract, pineapple juice, pear juice, and apple juice obtained by different CC techniques, respectively. In general, the CBCC effect on volatile compounds was varied, since some components increasing and others decreasing in each cycle. [PERSON] et al. [43] mentioned that the volatile compounds variation in a concentrate juice regard to the fresh juice is due to a synergistic effect between the esters (high concentration) with other compounds, resulting in an increases on other volatile compounds concentration, and thus, these can be identifiable by the chromatograph. This coincided with our results, since among for all the samples there was a decrease or increase in components, such as the appearance components, that are not identified in other cycles or fresh juice. Therefore, CBCC allows recovering certain components that are in low concentration in the fresh juice.