β-lactoglobulin and its thermolysin derived hydrolysates on regulating selected biological functions of onion skin flavonoids through microencapsulation

β-lactoglobulin and its thermolysin-derived hydrolysates were compared regarding the potential for microencapsulating of the flavonoids from yellow onion skins. Antioxidant activity of powders was of 500.28 ± 2.89 mMol Trolox/g dry weight (DW) for hydrolysates (P1) and 480.11 ± 4.45 mMol Trolox/g DW for whole protein (P2). Both powders showed antidiabetic activity against α-glucosidase, with inhibitory effect of 44.79 ± 0.58% for P1 and 32.76 ± 2.08% for P2. The bioinformatics analysis indicated that the Ala32-Ser37, Val59-Ile72, Leu111-Tyr118 and Val139-Ala148 amino acid sequences are particularly important for exerting potential antidiabetic activity. The finest powder was P2, with small 1–2 µm microspherosomes, whereas the peptides caused the agglutination of the flavonoids, leading to coacervates larger than 20 μm. Such an integrative approach might be useful in terms of recovering health-promoting bioactives from underutilized sources, such as onion skins and whey, contributing to the management and valorization of by-products, simultaneous with the development of innovative ingredients for functional applications.