*3.5. Antioxidant Capacity of Fresh and Dried Arils*

The antioxidant capacity of fresh pomegranate arils decreased significantly with storage time from 12.4 to 4.92 mM TE/ 100 mL RSA and 2.36 to 2.07 mM TE/ 100 mL FRAP (Table 3). In relation to their nutritional benefits, phenolic compounds in fruit contribute to the total antioxidant capacity and its subsequent human health benefits [49]. The observed increase in both TPC and TAC was inversely related to the antioxidant capacity (RSA and FRAP) exhibited by pomegranate fruit during storage at 7 ± 0.3 ◦C, with 92 ± 3% RH. This suggested that antioxidants often react differently depending on the type of antioxidant assay [50]. Siddhuraju et al. [51] reported that a decrease in reducing power could be attributed to the bioactive compounds—total phenolics, flavonoids, ascorbic acids and other hydrophilic antioxidants—associated with the component of the antioxidants present in the fruit.

For dried pomegranate arils, there were significant interactions on the antioxidant capacity (RSA, *p* < 0.023; FRAP, *p* < 0.0001) (Figure 5). The trend showed a general decrease in RSA and FRAP for both hot-air and freeze-dried arils after storage. The FRAP of freeze-dried arils was unchanged at 4 weeks also followed by gradual decline with the storage period (Figure 5) During the storage period, the RSA (26.9 and 29.5 mM TE/g DM) of hot-air dried arils was close to the values reported previously for hot-air dried pomegranate (22.7 to 30.6 mM TE/g) [52] and higher than papaya (9.72 mM TE/g) [53]. Our study showed similar FRAP (2.49–3.27 mM TE/g DM) in freeze-dried arils to those reported for pomegranate cv. Mollar de Elche (3.4 mM TE/g) [54].

**Figure 5.** Changes in the antioxidant capacity (**A**) RSA and (**B**) FRAP activity of pomegranate dried arils during 12 weeks of cold storage at 7 ± 0.3 ◦C, 92 ± 3% RH (w.b). HD, hot-air drying; FD, freeze-drying. D, drying methods; S, storage period (week). Different letters are significantly different (*p* < 0.05).

The decrease in the antioxidant capacity of dried arils could be attributed not only to the same observed decrease in the antioxidant capacity in fresh arils, but also to the thermal degradation of heat-sensitive phenolics—since TPC is reported to be the major contributors to antioxidant capacity. Additionally, Moser et al. [55] reported up to 25% reduction in antioxidant capacity in grape powder after 45 days of storage due to the formation of antioxidant polymers, such as low molecular weight procyanidins. This explanation was also supported by Mrad et al. [56]. However, Michalczyk et al. [57] reported that the antioxidant capacity of dried berries was retained during prolonged storage to a remarkably high degree, which is in contrast with the results from this present study.

Furthermore, freeze-drying amounted to approximately 12.1 and 22.9% lower antioxidant capacity (RSA and FRAP) after the storage period compared to the hot-air dried arils, respectively (Figure 5). Fracassetti et al. observed a similar decline in antioxidant activity while studying the storage of freeze-dried wild blueberry powder [58]. Mphahlele et al. [2] also reported better retention of antioxidants in the oven drying at higher temperatures 60 ◦C than in freeze-dried pomegranate peel. The authors attributed this to the concentration of compounds contained in the peel, as these are considered scavengers of free radicals produced during oxidation.
