Effects of malondialdehyde-induced oxidative modifications on the techno-functional and in-vitro digestive properties of α-Lactalbumin

α-lactalbumin, rich in essential amino acids, is widely used in infant formula and special medical foods containing polyunsaturated fatty acids, which may induce interactions between proteins and lipids/lipid derivatives during processing and storage. This study investigates the effects of malondialdehyde (MDA) oxidation, a typical product of lipid peroxidation, on the structure, functionality, and digestibility of α-lactalbumin. Spectroscopic techniques showed that MDA incubation altered the secondary and tertiary structure of α-lactalbumin and increased its surface hydrophobicity. After MDA modification, the rehydrated particle size of α-lactalbumin increased from ∼2.00 nm to ∼13.00 nm, and SDS-PAGE results confirmed the presence of protein crosslinking and aggregation. Additionally, MDA modification reduced the solubility and interfacial properties of α-lactalbumin. In vitro gastrointestinal digestion results showed that MDA modification delayed protein hydrolysis, which finally increased the abundance of high-molecular-weight peptides, and decreased the release of free amino acids. This is probably due to MDA-induced protein aggregation, which shields the hydrolysis sites of digestive enzymes, enhancing resistance to proteolysis. The findings of this study provide a theoretical basis for elucidating lipid–protein interactions and their consequences in complex food systems, offering valuable insights for the formulation design and monitoring of nutritional component changes during processing and storage.