On the role of bile salts in the digestion of emulsified lipids

The objective of this study was to understand quantitatively the role that bile salts play in the digestion of emulsified lipids. The behaviours of digestion by pancreatin (1.6 mg/mL) of sodium-caseinate-stabilized emulsions (0.5 wt% protein) and bile-extract-stabilized emulsions (0.2–5 mg/mL) as influenced by the addition of aqueous bile extract were studied under simulated intestinal conditions (37 °C; pH 7.5; 39 mM K2HPO4, 150 mM NaCl; with continuous agitation at ∼ 150 rev/min for 3 h). The droplet characteristics (size and ζ-potential) of the sodium caseinate- and bile extract-stabilized droplets were evaluated by light scattering techniques. The kinetics of the total fatty acids released by hydrolysis of the emulsified lipids were monitored by the pH-stat method with or without the presence of continuous phase bile extract. The results suggested that the presence of unadsorbed bile extract markedly enhanced the rate and the extent of lipid digestion. This could be attributed to considerable removal of lipolysis products (free fatty acids, mono- and/or di-acylglycerols) in mixed micelles, which are known to inhibit lipid digestion, by the unadsorbed bile salts. This study provides new insights for the lipid digestion of food formulations.