CHARACTERIZATION OF EMULSIONS AND LIPOLYSIS OF DIETARY LIPIDS IN THE HUMAN STOMACH

Characterization of emulsions and lipolysis of dietary lipids in the human stomach. Am. J. Physiol. 266 (Gastrointest. Liver Physiol. 29): G372-G381, 1994. - Fasting subjects were intragastrically intubated and received a coarsely emulsified test meal. Gastric aspirates were collected after 1, 2, 3, and 4 h. During digestion in the stomach, unemulsified lipids (greater than or equal to 100 mu m) represented a minor fraction. A significant amount of the large 70- to 100-mu m lipid droplets disappeared, and fine 1- to 10-mu m droplets were generated. The median lipid droplet diameter significantly decreased (21.9 vs. 52.9 mu m) after 1 h and kept intermediate values for longer periods of time. The emulsion surface area was 100-120 m(2)/l and was basically provided by 1- to 100-mu m droplets. Lipolysis catalyzed by gastric lipase primarily occurred within the first hour of digestion (11.9%). Smaller droplets were enriched in triglyceride lipolytic products. The free fatty acid concentrations were in the range of 5.6-8.2 mill over 1-4 h. The present finding demonstrates for the first time that in the human stomach most dietary lipids are present in the form of emulsified droplets, in the range of 20-40 mu m, and that gastric lipolysis can help to increase emulsification in the stomach.