Optimization of Conventional Extraction Parameters for Recovering Phenolic Compounds from Potato (Solanum tuberosum L.) Peels and Their Application as an Antioxidant in Yogurt Formulation

The aim of this work was to optimize the conventional parameters for the extraction of phenolic compounds from potato (Solanum tuberosum L.) peels (PP). A central composite design (CCD) was used to establish the impacts of ethanol concentration (%), extraction time (min), and liquid/solid ratio (mL/g). The optimal experimental conditions that maximized extraction were ethanol at a concentration of 80% (v/v) for a time of 150 min with a ratio of 1 g/30 mL. Under optimal conditions, the total phenolic content (TPC) and the total flavonoid content (TFC) were 204.41 ± 8.64 mg GAE/100 g DW and 21.47 ± 0.76 mg QE/100 g DW, respectively. The PP extract had a potent antioxidant capacity tested by phosphomolybdate and DPPH assays with IC(50) of 10.65 ± 0.21 and 179.75 ± 3.18 µg/mL, respectively. Furthermore, by fortifying yogurt with PP as a natural ingredient, an improvement ofits physical, nutritional, antioxidant, and sensorial qualities was attempted in this study. The yogurts formulated with PP revealed significantly higher (p ≤ 0.05) TPC, TFC, and antioxidant capacity in comparison with the control sample. In addition, the sensory evaluation showed that the yogurts enriched with PP were preferred over the control yogurt. The results indicate that PP can be considered an interesting byproduct since it can improve the nutritional, bioactive, and sensorial profile of yogurt, highlighting that PP, due to its high phenol content, can substantially improve the antioxidant effect of the new formulated yogurt.