## 3 Results and Discussion  
### Bioactive Compounds and Antioxidant Activity  
The water content of the fruit batch used in this study was x\({}_{\text{w}}\) 85.8 \(\pm\) 0.3 g/100 g for K and 89.9 \(\pm\) 1.3 g/100 g for S and decreased to around 2.5 \(\pm\) 0.1 g/100 g for the corresponding freeze-dried samples. The concentration of each phytochemical component analysed and the AOP of kiwifruit and strawberry samples are shown in Table 1 and Figure 1. In general, the TP of kiwifruit samples was lower than in strawberries. The initial TP of fresh fruit samples varied from 349 to 2237 mg GAE/100 g db in K and S, respectively. K presented values similar to those reported by [PERSON] et al. (2009) [31], and S showed higher TP than those obtained in other studies with different strawberry varieties [32]. This variability can be attributed to the different fruit variety or states of maturity and the different solvents used in the extraction process. Generally, plant preparations are marketed in the form of liquid extracts or as powders resulting from the drying of plant material or the liquid extracts themselves. Solid forms (powders) of plants are being used increasingly because they offer numerous advantages over liquid extracts: ease of standardization; greater physical, chemical, and biological stability; lower transport and storage costs; and the possibility of achieving higher concentrations. For all these reasons, dehydration of samples is a crucial step in order to achieve a product that is suitable for industrial use. However, it is important to bear in mind that dehydration, to some extent, can affect the activity and stability of bioactive compounds due to chemical, enzymatic, and enzymatic degradation and losses through volatilisation and/or thermal degradation. The freeze-drying technique was chosen in this study because of its benefits over other dehydration techniques [21]. The comparison of K and S data with the corresponding KD and SD extracts showed that the freeze-drying process favoured (\(p<0.05\)) the extraction of phenolic compounds. An increase in TP up to 6.48% and 8.85% was observed for kiwi and strawberry, respectively (Equation (1)). This rise could be explained based on the breaking of the remaining cellular structure of the fruit puree due to the ice crystals formed during the freezing step. In this way, the subsequent entry of the solvent is facilitated, and consequently, the extraction of the TP may be improved. The high porosity characteristic of freeze-dried products can also contribute in this sense. Other studies have also shown that the freeze-drying process increases the amount of phenolic compounds [33; 34]. Freeze drying caused a reduction in the particle size of the sample, which favoured the contact surface with the solvent and could cause an increase in yield extraction. TP are considered important contributors to AOP in fruits. This activity may be related to several properties such as redox characteristics, which allow them to act as reducing agents, hydrogen donors, singlet oxygen quenchers, and even metal chelators [35]. Spectrophotometric techniques are helpful for estimating the TP and the antioxidant capacity. However, more selective techniques, such as chromatographic ones, must be utilised to determine the individual polyphenic profile. Figure S2 (Supplementary Material) illustrates an example of an obtained chromatogram, and Figure 1 shows the content of each of the phenolic compounds identified in the fresh fruits and in the corresponding KD (Figure 1a) and SD (Figure 1b) methanolic extracts. The percentage of changes due to the freeze-drying process (Equation (1)) has also been included. The molecules were classified as different phenolic compounds: phenolic acids (ferulic and ellagic acid), flavonoids (quercetin and epicatechin), and anthocyanins (pelargonidin-3-glucoside).