## 3 Results and Discussion
### Bioactive Compound Content and Antioxidant Activity Determinations  
The fresh apple juice had TPC, TFC and TFLC values (Table 2) of approximately 244 mg GAE/100 g d.m., 82 mg CEO/100 g d.m., and 124 mg CEQ/100 g d.m., respectively, which were significantly higher than those previously informed by [PERSON] et al. [36]. The difference in results could be explained by factors, such as type of harvesting, ripening stage, climatic conditions in the fresh fruits, and/or specific methods used during juice preparation [37].  
Figure 3: Samples of apple juice: (**a**) fresh juice; (**b**) cryoconcentrated sample (3 rd cycle).  
At each CBCC cycle, the results increased significantly (\(p\leq 0.05\)) when the bioactive compounds content were compared to the fresh apple juice, and in the final cycle, the concentrates samples exhibited values close to 819 mg GAE/100 g d.m., 248 mg CEO/100 g d.m., and 345 mg CEO/100 g d.m. for TPC, TFC, and TFLC, respectively. Hence, the cryoconcentrated samples presented an increase up to 3.4 (TPC), 3.0 (TFC), and 2.8 (TFLC) times compared to the initial value. This tendency has been observed with liquid samples such as orange juice [14], strawberry juice [15], blueberry juice [17], pineapple juice [19], yerba mate [38], and coffee extract [39] obtained by the various CC techniques.  
Similarly, from the TBC results, the retention was calculated at each cycle. From the first cycle, the TBC retention was more than 60%, which allows highlighting the potential advantage, in TBC retention terms, of cryoconcentration as non-thermal concentration technology. Specifically, the TBC retention was approximately 66%, 77%, and 85% for TPC, 63%, 71%, and 77% for TFC, and 61%, 64%, and 71% for TFLC along the cycles. [PERSON] et al. [17, 19] and [PERSON] et al. [39] presented comparable values for fruit juices with CBCC and aqueous coffee extract with FFCC. Specifically, the studies informed TBC retention values from 70% to 95% and 90%, respectively. Thus, TBC retention shows the beneficial CBCC effects to obtain a liquid fraction with high TSSC values and attractive color and, in addition, this emerging technology allows the preservation of important thermolabile bioactive compounds in the final cryoconcentrate.  
In antioxidant activity terms, the DPPH and FRAP assays showed a value close to 523 \(\upmu\)mol TE/100 g d.m. and 467 \(\upmu\)mol TE/100 g d.m for the fresh apple juice, respectively, which was higher than previously reported by [PERSON] et al. [40]. The variation could be related to the growth conditions of apple fruits and the methodology used to obtain the fresh juice, which, in turn, influences the anthocyanins content (main contributors in antioxidant capacity) [41]. Thus, the values exhibited an increasing with significant differences (\(p\leq 0.05\)) as the cycles progressed. CBCC presented values of approximately 1040 \(\upmu\)mol TE/100 g d.m., and 1277 \(\upmu\)mol TE/100 g d.m. (1 st cycle) to 1803 \(\upmu\)mol TE/100 g d.m. and 2936 \(\upmu\)mol TE/100 g d.m. (3 rd cycle) for DPPH and FRAP, respectively. As mentioned above, this behavior could be associated with the use of low temperatures in CBCC to concentrate bioactive compounds, since the damage to the sensitive components is minimal and, therefore, this process allows a higher anthocyanin concentration than other concentration technologies. A similar trend was observed by [PERSON] et al. [39] and [PERSON] et al. [40] during the freeze concentration of coffee extract and apple juice, respectively.