Microplastics Interact with β-lactoglobulin: Implications for Protein Structure, Digestibility, and Allergenicity

Microplastics are pervasive throughout the food system. Recent research indicates that millions of microplastics are released from baby bottles during infant formula preparation. In this context, microplastics are likely to interact with milk allergens, potentially affecting the structures and characteristics of allergens, which may pose risks to human health, particularly for infants with cow's milk allergy. This study analyzed the interaction between commonly used baby bottle microplastics (polypropylene, polyethersulfone, polyphenylsulfone) and the major milk allergen β-lactoglobulin using multi-spectroscopy techniques and molecular simulation. Furthermore, microplastics-mediated alterations in protein digestibility and allergenicity were evaluated through in vitro gastrointestinal digestion, peptidomics, ELISA, and a KU812 cell degranulation model. The results indicated that microplastics adsorbed β-lactoglobulin through nonpolar interactions, with the surface chemistry of microplastics determining the binding affinity. Microplastics induced the unfolding of β-lactoglobulin tertiary structure, and β-lactoglobulin mixed with microplastics resulted in reduced digestibility. Moreover, β-lactoglobulin that interacted with microplastics showed enhanced IgE binding capacity and a greater ability to elicit KU812 cell degranulation. This effect was especially pronounced with polyphenylsulfone@β-lactoglobulin, whose IgE binding capacity increased by 3.7%, while the release of β-hexosaminidase and histamine increased by 9.4% and 65.5%, respectively. Collectively, these findings provide novel insights into the interactions between microplastics from baby bottles and milk allergens, highlighting potential implications for cow's milk allergy management and broader health risks associated with microplastics exposure in infant nutrition.