Pancreatin-induced coalescence of oil-in-water emulsions in an in vitro duodenal model

The behaviour of cationic lactoferrin-stabilized and anionic β-lactoglobulin (β-lg)-stabilized oil-in-water emulsions (20.0% (w/w) soy oil, 1.0% (w/w) protein) in the presence of simulated intestinal fluid (SIF) containing physiological concentrations of pancreatin (0.0–10.0 mg mL−1) and/or bile salts (0.0–25.0 mg mL−1) at 37 °C, pH 7.5 and inorganic salts (39 mm K2HPO4, 150 mm NaCl and 30 mm CaCl2) was investigated. Both emulsions showed a significant degree of coalescence and fatty acid release on mixing with SIF. Appreciably negative ζ-potential values (≥−50 mV) for both types of emulsion droplet at the highest pancreatin/bile salts concentration could be attributed to displacement of and/or binding to the interfacial proteins by bile salts, together with interfacial proteolysis by pancreatin, which enhanced the potential for lipase to act on the hydrophobic lipid core, thus generating free fatty acids and possibly mono- and/or diglycerides at the droplet surface.