Influence of electrostatic heteroaggregation of lipid droplets on their stability and digestibility under simulated gastrointestinal conditions.

There is emerging interest in the impact of food structure on lipid digestion and its relationship to human nutrition. The objective of this study was to investigate the influence of heteroaggregation of lipid droplets on their potential biological fate using a simulated gastrointestinal tract (GIT). At neutral pH, a highly viscous "mixed emulsion" was formed by mixing anionic β-lactogobulin (β-Lg) coated lipid droplets with cationic lactoferrin (LF) coated lipid droplets due to electrostatic attraction. We compared the behavior of β-Lg-emulsions, LF-emulsions and mixed emulsions under in vitro oral, gastric, and small intestinal conditions. In the oral stage, the β-Lg emulsion and mixed emulsion were stable but the LF emulsion aggregated, which was attributed to electrostatic interactions with mucin. In the gastric stage, extensive droplet aggregation occurred in all three emulsions, which was attributed to proteolysis of adsorbed proteins by pepsin, as well as the influence of high acidity and ionic strength on electrostatic interactions. Despite the differences in the initial compositions and microstructures of the three emulsions, we did not observe an appreciable difference in the rate or extent of their lipid digestion in the small intestine. Qualitatively similar results were obtained using a simple GIT model (small intestine only) and the full GIT model (oral, gastric, and small intestine). The knowledge gained from this study will be useful for the creation of functional foods to improve health and well-being.