Triglyceride emulsification by amphipaths present in the intestinal lumen during digestion of fat

Abstract

The mechanism of emulsification of ingested liquid triglyceride has been given theoretical consideration but minimal experimental study. The present studies have investigated the capacity of bile salts, phosphatidylcholine, monolein, and oleic acid for triglyceride emulsification using triolein as a test triglyceride, emulsification being induced by slow rotation. Bile salts alone emulsified small amounts of triolein but, as expected, fatty acid soaps and phosphatidylcholine alone produced concentrated emulsions of great stability. However, when fatty acid soaps, monolein, and phosphatidylcholine singly or in combination were mixed with bile salts in concentrations above the critical micellar concentrations (combinations that are present in the upper small intestine), decreasing emulsification was observed. The surface or emulsifying activity of amphipaths was dependent upon their availability to the oil-aqueous interface, which appeared to be inversely related to their incorporation into micelles. Using low-shear forces the particle size distribution did not vary greatly with the amphipaths studied although mean particle size fell slightly with increasing taurocholate concentration. Larger and less variable particles were made using high-shear systems. The combination of bile salts and lipolytic products present in the intestine may readily participate in triglyceride emulsification with low shear.