The effects of soy lecithin on foaming behavior and digestion properties of infant formula model system

The formation of undesirable foam during the reconstitution of infant formula has become a challenge, leading to feeding difficulties and reduced product stability. Soybean lecithin (SL) is widely used in infant formula as an emulsifier, where it interacts with proteins to modulate interfacial composition and emulsion structure. This study aimed to address this problem by investigating the effect of SL (0-0.21%) on the foaming behaviors, digestion properties, and stability properties of the infant formula emulsion prepared with infant formula protein model system (IFPMS). Multispectral techniques were utilized to study the interactions between SL and IFPMS. The results verified that the IFPMS-SL complex was formed through hydrogen bonds and hydrophobicity bonds. The incorporation of SL resulted smaller particle size, higher absolute charge, and higher emulsion stability. Additionally, SL significantly enhanced lipid digestion, as evidenced by a marked increase in free fatty acid (FFA) release. The smaller particle size and higher net charge of digestive products could stabilize the emulsion and prevent flocculation. As the SL concentration higher than 0.14%, it dramatically decrease the foam volume of emulsions and promote the foam disappeared within 15 min. The higher interfacial pressure and lower dilatational modulus indicated that SL may compete with the protein and change the composition at air-water interface. Furthermore, capillary electrophoresis (CE) photographs revealed that the casein in foam phase was gradually decreased, as compared with control, further revealed that casein was replaced by SL during foam process. These findings provide mechanistic insights into SL's role in improving infant formula quality by reducing foaming and enhancing digestibility/stability, supporting its application in optimized product development.