## 2 Materials and Methods  
### Material  
Grape pomace var. Tintorera was collected in the Itata Valley, Nuble Region, (36\({}^{\circ}\)37\({}^{\prime}\)6.96\({}^{\prime\prime}\) S, 72\({}^{\circ}\)19\({}^{\prime}\)30.81\({}^{\prime\prime}\) W) in the 2021 season. The pomace was frozen and transported to the BIOINVE (Bioactive Compounds and Ingredients from Plants Laboratory, Faculty of Agronomy, University of Concepcion, Concepcion, Chile) and kept at \(-\)80 \({}^{\circ}\)C until analysis.  
Preparation of the Microencapsulated Supplement by Spray Drying and Characterization of the Grape Pomace Powder (GPP)  
Batchs of 500 g of grape pomace were mixed with 96% ethanol (\(w/v\)) following the methodology described by [PERSON] et al. [27]. Maltodextrin DE-10 at 20% (\(w/v\)) was used as wall material and was acquired from the Sigma Aldrich Chemical Co. (MilliporeSigma, St. Louis, MO, USA). The mini spray-dryer B-290 (Buchi, Flawil, Switzerland) was fed with the aforementioned solution and was homogenized by constant agitation at room temperature and at a flow rate of 4 mL min\({}^{-1}\). The inlet temperature was maintained at 120 \({}^{\circ}\)C, whereas the outlet air temperature was 80 \({}^{\circ}\)C (Table S1). The powder obtained was collected in an opaque, air-tight container at 4 \({}^{\circ}\)C for additional analysis. The morphological characterization of the grape pomace powder (GPP) was carried out by Scanning Electron Microscopy (SEM) (FEI-Inspect S50, FEI Company, Hillsboro, OR, USA). GPP samples were prepared and attached to double-sided adhesive tape mounted on SEM stubs, covered with a gold layer (9 nm) under vacuum SEM working at 5 kV, with 10,003 and 50,003 magnifications. Finally, loading capacity (quantity of total phenolic compounds per 100 grams of powder), entrapment efficiency (g total phenolic compounds encapsulated 100 g\({}^{-1}\) phenolic compounds from pomace added) and powder recovery (ratio between the quantities of powder versus the initial mass solids) were calculated (Table S2). Total phenolic compounds (g) were obtained by HPLC-DAD at 280, 320, 360 and 520 nm similar to that described in Section 2.3.  
Characterization and Quantification of Phenolic Compounds and Antioxidant Properties from Grape Pomace Powder  
The extraction and chemical characterization of the GPP was performed according to the methodology described by [PERSON] et al. (2016). Phenolic compounds were extracted and quantified by a Hitachi HPLC-DAD system (Hitachi technologies, MERCK, Darmstadt, Germany) using the same chromatographic conditions described by [PERSON] et al. (2016), recording chromatograms at 280, 320, 360 and 520 nm. Some external standards were used for quantification, such as gallic acid (99%), (+)-catechin (99%), epigallocatechin gallate (95%), 3-hydroxytrosol (99%) and tyrosol (99) at 280 nm, chlorogenic acid (97%), caffe acid (99%), coumaric acid (99%), ferulic acid (99%) and _trans_-resveratrol (99%) at 320 nm, quercetin hydrate (95%), quercetin 3-O-glucose (90%), myricetin 3-O-glucose (96%), kaempfer 3-O-glucose (99%) at 360 nm, malvidin 3-O-glucose (95%) and cyanidin 3-O-glucose (99%) at 520 nm, (Sigma-Aldrich, St. Louis, MO, USA). All of the solvents used in the extractions were of analytical grade and were obtained from Merck (Darmstadt, Germany). The results were expressed in mg 100 g\({}^{-1}\) DW.  
The antioxidant activity was determined by DPPH* (2,2-diphenyl-1-picrylhydrazyl) and ORAC (oxygen radical absorbance capacity) assays ([PERSON] et al., 2016; [PERSON] et al., 2016). Briefly, the antioxidant capacity for ORAC-FL was estimated by measuring the changes in fluorescence after 120 min of reaction with the radical, whereas DPPH* was evaluated by determining the variation in absorbance at 515 nm after 30 min of reaction with the radical. Both assays were performed using a 96-well micro in a Synergy H1 hybrid multi-mode microplate reader (Biotek, Winooks, VT, USA), and the results were expressed as umol Trolox 100 g\({}^{-1}\) DW. Six replicates were accomplished for each analysis.