Acidification of lactoferrin-casein micelle complexes in skim milk

Lactoferrin-Based Heteroprotein Systems, From Their Formation Mechanism, Properties, To Applications

Lactoferrin (LF) is an important iron-binding glycoprotein found in milk and mucosal secretions. The alkaline lactoferrin can interact with some acidic proteins to form heteroprotein systems with multifunctional properties and a wide range of applications. Lactoferrin can interact with animal and plant proteins mainly through the electrostatic forces, dipolar attraction, and hydrophobic interactions. In this review, the types of heteroprotein complexes formed by the complex coacervation of lactoferrin with other proteins are introduced, including the preparation, structure, and applications. The factors affecting the formation of heteroprotein complexes are described, such as pH, ionic strength, mixing ratio, total protein concentration, and temperature. The issues and challenges in the formation of heteroprotein complexes are also discussed.

Research Advances of Lactoferrin in Electrostatic Spinning, Nano Self-Assembly, and Immune and Gut Microbiota Regulation

Lactoferrin (LF) is a naturally present iron-binding globulin with the structural properties of an N-lobe strongly positively charged terminus and a cage-like structure of nano self-assembly encapsulation. These unique structural properties give it potential for development in the fields of electrostatic spinning, targeted delivery systems, and the gut-brain axis. This review will provide an overview of LF's unique structure, encapsulation, and targeted transport capabilities, as well as its applications in immunity and gut microbiota regulation. First, the microstructure of LF is summarized and compared with its homologous ferritin, revealing both structural and functional similarities and differences between them. Second, the electrostatic interactions of LF and its application in electrostatic spinning are summarized. Its positive charge properties can be applied to functional environmental protection packaging materials and to improving drug stability and antiviral effects, while electrostatic spinning can promote bone regeneration and anti-inflammatory effects. Then the nano self-assembly behavior of LF is exploited as a cage-like protein to encapsulate bioactive substances to construct functional targeted delivery systems for applications such as contrast agents, antibacterial dressings, anti-cancer therapy, and gene delivery. In addition, some covalent and noncovalent interactions of LF in the Maillard reaction and protein interactions and other topics are briefly discussed. Finally, LF may affect immunological function via controlling the gut microbiota. In conclusion, this paper reviews the research advances of LF in electrostatic spinning, nano self-assembly, and immune and gut microbiota regulation, aiming to provide a reference for its application in the food and pharmaceutical fields.

Modification of protein structures by altering the whey protein profile and heat treatment affects in vitro static digestion of model infant milk formulas

Heat treatments induce changes in the protein structure in infant milk formulas (IMFs). The present study aims to investigate whether these structural modifications affect protein digestion. Model IMFs (1.3% proteins), with a bovine or a human whey protein profile, were unheated or heated at 67.5 °C or 80 °C to reach 65% of denaturation, resulting in six protein structures. IMFs were submitted to in vitro static gastrointestinal digestion simulating infant conditions. During digestion, laser light scattering was performed to analyze IMF destabilization and SDS-PAGE, OPA assay and cation exchange chromatography were used to monitor proteolysis. Results showed that, during gastric digestion, α-lactalbumin and β-lactoglobulin were resistant to hydrolysis in a similar manner for all protein structures within IMFs (p > 0.05), while the heat-induced denaturation of lactoferrin significantly increased its susceptibility to hydrolysis. Casein hydrolysis was enhanced when the native casein micelle structure was modified, i.e. partially disintegrated in the presence of lactoferrin or covered by heat-denatured whey proteins. The IMF destabilization at the end of the gastric digestion varied with protein structures, with larger particle size for IMF containing native casein micelles. During intestinal digestion, the kinetics of protein hydrolysis varied with the IMF protein structures, particularly for IMFs containing denatured lactoferrin, exhibiting higher proteolysis degree (67.5 °C and 80 °C vs. unheated) and essential amino acid bioaccessibility (67.5 °C vs. unheated). Overall, the protein structures, generated by modulating the whey protein profile and the heating conditions, impacted the IMF destabilization during the gastric phase and the proteolysis during the entire simulated infant digestion.