## 4 Discussion
### Impact of Each Equivalent Processing Condition on the Antioxidant Activity  
Antioxidant compounds play a major role protecting cells from reactive oxygen species, which can contribute to the development of chronic diseases or other disorders. Apples are a reliable source of antioxidant compounds such as quercetin, catechchin, chlorogenic acid, and phloridzin that have been associated with several health benefits (lower changes in heart diseases, cancer, diabetes, etc.) [48]. However, it is noteworthy that the antioxidant content of apples may vary depending on the apple cultivar, growing conditions, and, ultimately, processing methods.  
The antioxidant capacity of apple puree, as determined through DPPH and ABTS assays, has been addressed in several papers. The antioxidant activity of Reineta Parda AP produced in this study was 0.195 \(\pm\) 0.02 mmol/100 g Trolox, surpassing that of the Idared variety (0.16 mmol Trolox/100 g) [41], yet not reaching the levels found in the Shampion variety (0.40 mmol Trolox/100 g) [41]. Such variability in antioxidant activity could be attributed to multiple factors including the diversity and quantity of phytochemicalspresent, differences in total phenolic content, and the distinct structural and functional properties of these phytochemicals across various apple varieties [49]. Apples are notably rich in polyphenolic compounds such as flavonoids and phenolic acids, renowned for their antioxidative properties. Nonetheless, the polyphenol profile, including the content and composition, can vary significantly among different apple varieties, influenced by factors such as the cultivar, stage of ripeness, and environmental conditions. The structural variations in flavonoids are also known to affect their antioxidative potency [50].  
Regarding the ABTS assay, the antioxidant capacity of Reineta Parda apple puree was measured at 0.242 \(\pm\) 0.006 mmol Trolox/100 g, markedly lower than the values recorded for purees from Granny Smith (7.35 mmol Trolox/100 g) [51], Gold Rush (12.78 mmol Trolox/100 g) [51], Idared (0.54 mmol Trolox/100 g) [41], and Shampion (1.27 mmol Trolox/100 g) [41] varieties. This discrepancy could be ascribed to the same factors mentioned earlier, highlighting the significant impact of phytochemical diversity, phenolic content, and the specific properties of these compounds on the antioxidant potential of different apple cultivars.  
For both DPPH and ABTS, the increase in the antioxidant activity of AP right after BL is remarkable, and it increased even more after each processing condition. This may be attributed to an increased extraction (due to the disruption of cell walls and release of cellular content to the external media) and solubilization of compounds with antioxidant capacity, which will ultimately lead to an increment in the antioxidant activity.  
These results highlight that these processing technologies not only can be used to ensure food safety, but also to enhance the bioavailability of antioxidant compounds, which are known to have key health-promotion abilities and could allow the formulation of functional foods [52]. Additionally, as AP can be used as an ingredient for other food products, enhancing its antioxidant activity with these emergent technologies can considerably contribute to the development of other apple-based functional foods, like smoothes, yoghurts, fruit jams, etc.