## 4 Discussion
### Impact of Each Equivalent Processing Condition on Physicochemical Parameters
The observed variations may be attributed to changes in apple cultivars, differences in heat treatments, and the comparatively milder thermal treatments used in this study in terms of both duration and temperature, as compared to previous research. The \(\Delta\)E* obtained in the previously mentioned work by [PERSON] and colleagues [37] was at the lowest for the HPP-treated AP samples, followed by the ohmic and the conventional thermal treatment, which is similar to what was observed by [PERSON] and colleagues in their work with Golden Delicious AP treated by HPP (6 bar, 1 min at 4 \({}^{\circ}\)C), a mild thermal treatment (99 \({}^{\circ}\)C, 1 min) and a standard treatment (92 \({}^{\circ}\)C, 5 min). The authors noted that the \(\Delta\)E* was the lowest for HPP, followed by the mild and the standard thermal treatments, respectively [39]. These results partially coincide with the findings of the present study, where HPP-treated AP showed a lower \(\Delta\)E* for HPP when compared tothe CTP-treated AP but the BL-treated AP was the lowest of all the treatments, perhaps due to its effect on inactivating enzymes like polyphenol oxidase, which are involved in enzymatic browning starting immediately after the mechanical damage induced to the cells during homogenization [42]. Regarding the effects PEF on colour attributes, [PERSON] et al. [43] observed that AP produced from the Golden Delicious variety, subjected to PEF treatment at 20 to 30 kV and a frequency of 800 Hz, featuring pulse fronts between 50 and 200 ns and a pulse duration of 1 ms, exhibited no immediate alterations in colour post-treatment. This outcome is consistent with untreated control samples, corroborating the findings of the current research. Similar findings were reported by [PERSON] and colleagues [15] for apple juice processed by PEF (12.3 kV/cm, 94 Hz, 132.5 kJ/L and 12.5 kV/cm, 62 Hz and 76.4 kJ/L) who compared the processing conditions with thermal pasteurization (72 \({}^{\circ}\)C/15 s and 80 \({}^{\circ}\)C for 30 s) and HPP (400 and 600 MPa for 3 min). In terms of impact on quality attributes such as colour, cloud stability, taste, and aroma, severe thermal processing (85 \({}^{\circ}\)C/15 s) produced the brightest colour compared to the other processing conditions [15]. The stability of colour attributes in fruit juices and pulps is heavily influenced by various factors, including the ripening stage of the fruit, pH levels, processing temperature (which affects both Maillard and caramelization reactions), indigenous enzymes (such as polyphenol-oxidase and peroxidase), and exposure to oxygen. Therefore, it is crucial to take into account these elements when establishing processing conditions for fruit juices and pulps. However, the impact of these factors can be managed through the use of additions, such as ascorbic acid (often referred to as vitamin C) or other substances [44]. When considering the AP pH values reported in the literature, the pH value of the control Reineta Parda AP (3.53 \(\pm\) 0.01) was higher than those reported for Granny Smith AP (3.2 [36] and 3.4 [45]), similar to Braeburn and Gold Delicious AP (3.6 and 3.7, respectively [45]) and lower than an industrial AP (11 \({}^{\circ}\)Brix) and a thermal treated AP (3.86 [46] and 3.85-3.90 [37], respectively). Except for the PEF-treated AP samples (10.77 \({}^{\circ}\)Brix), the TSS values obtained fit well within reported AP TSS values that range from 11 \({}^{\circ}\)Brix (industrial AP) [46] to 17.4 \({}^{\circ}\)Brix (Golden Delicious AP) [47] for different apple cultivars, including Braeburn, Golden Delicious, Golden Smoothee, Granny Smith and Royal Gala [36; 37; 45; 47]. A study tested the physicochemical properties of Bramley's seedling AP enriched with two prebiotics (8% _w/w_) (inulin and fructologosaccharides) immediately after processing (thermal and HPP) and during storage (30 days at 4 \({}^{\circ}\)C). After 30 days, no change in pH was observed for the treated and untreated samples for AP containing either prebiotic.