*2.3. Antioxidant Capacity*

The antioxidant capacity (AC) was measured by a ferric reducing antioxidant power assay (FRAP) [23,24]. Extracts were obtained in the same way as for TPC determination. Distilled water (30 μL), the sample (30 μL), and FRAP reagent (900 μL) were placed in the cuvette. The cuvettes were incubated for 30 min in a water bath at 37 ◦C and the absorbance was measured at 595 nm. A calibration curve was obtained using different concentrations of Trolox in 960 g kg−<sup>1</sup> ethanol. The results were expressed as μmol Trolox/mL of sample. Three separate extractions were made for each treatment and the measurements were performed in triplicate.

### *2.4. Chokeberry Microstructure*

The microstructure analysis was carried out following Hernández-Carrión et al. [25] with some modifications. For the study of the chokeberry microstructure, a Nikon Eclipse E80i microscope (Nikon, Tokyo, Japan) was used. The autofluorescence of the phenolic compounds in the samples was observed using a mercury arc lamp with a tetramethyl rhodamine filter (λex = 543/22 nm, λem = 593/40 nm) as the excitation source. Samples were visualized using ×10 and ×20 objective lenses. The micrographs were stored at a 1280 × 1024-pixel resolution using the microscope software (NIS-Elements F, Version 4.0, Nikon, Tokyo, Japan). Analysis of the fluorescence intensity was conducted with the ImageJ software.
