Integrated extraction of phenolic-rich apple peel extracts and in silico evaluation of quercetin dairy protein interactions

Apple peel (Malus sp.), a by-product of fruit processing, is rich in phenolic compounds, particularly quercetin, as well as other flavonoids and dietary fiber. This study integrated conventional maceration with Microwave-Assisted Extraction (MAE) to obtain phenolic- and flavonoid-rich apple peel extracts and to explore their potential interaction with major dairy proteins through in silico docking. Apple peel powders were first macerated and then subjected to MAE at irradiation times (3, 6, 9, and 12 minutes). The extracts were assessed for antioxidant activity (DPPH), total phenolic content (TPC), and total flavonoid content (TFC), with all experiments performed in triplicate and analyzed using one-way ANOVA followed by an appropriate post hoc test. Prolonged MAE treatment enhanced antioxidant activity (93.85–95.09%), phenolic content (13.52–14.73 mg GAE/g), and flavonoid content (23.76–29.62 ppm). Molecular docking indicated that quercetin showed comparable predicted binding affinity toward both milk proteins, with binding energy values of −6.7 kcal/mol for β-lactoglobulin and −6.9 kcal/mol for α-lactalbumin. These findings suggest that apple peel extract obtained through integrated extraction may have potential for future application in dairy-based functional systems, although formulation and stability studies are still required.