Abstract: As an emerging ingredient for infant formula, milk fat globule membrane (MFGM)-enriched whey protein isolate (M-WPI) has attracted widespread interest in recent years. This study analyzed and compared the amino acid composition, protein solubility, phospholipid distribution, particle size, and zeta potential of M-WPI from three different sources (Hilmar M-WPI, Friesland M-WPI, and Fonterra M-WPI) along with changes in their microstructure and protein hydrolysis characteristics during in vitro simulated infant digestion. Furthermore, three M-WPI emulsions were constructed and analyzed for their structural properties using confocal laser scanning microscopy (CLSM) and Fourier transform infrared (FTIR) spectroscopy. The results showed that compared with Fonterra M-WPI, Hilmar and Friesland M-WPI exhibited higher hydrophilic amino acid relative contents, better protein solubility, smaller particle size, and faster digestion rates. Differences were observed in the simulated infant digestion tolerance of MFGM proteins among the three M-WPI samples, with butyrophilin demonstrating higher digestive stability in the gastric phase. Additionally, emulsions prepared with all three M-WPIs formed phospholipid-coated, breast milk-like fat globule interfacial structures to varying degrees. The findings of this study provide theoretical support for the application and formulation optimization of M-WPI from different sources in infant formula and functional dairy products.

Key words: milk fat globule membrane-enriched whey protein isolate; in vitro simulated infant gastrointestinal digestion; in vitro protein digestion; humanized milk fat globule membrane