EFFECTS OF DROPLET SIZE, TRIACYLGLYCEROL COMPOSITION, AND CALCIUM ON THE HYDROLYSIS OF COMPLEX EMULSIONS BY PANCREATIC LIPASE - AN INVITRO STUDY

The pancreatic lipase-catalyzed hydrolysis of complex lipid emulsions dedicated to enteral nutrition in humans was studied in vitro. The four complex emulsions used had variable triglyceride composition and particle sizes, and a similar phospholipid content. They contained triglycerides in the form of pure medium-chain triglycerides (MCT), pure long-chain triglycerides (LCT), or a mixture of MCT and LCT (MCT/LCT 20/80 wt/wt). The mean droplet sizes of the emulsions were 0.19-mu-m (MCT), 0.43-mu-m (LCT), 0.46-mu-m, or 3.18-mu-m (MCT/LCT). The phase distribution of phospholipids (emulsified particles/aqueous medium) was shown to be related to the saturation of the available triglyceride interface area. The presence of MCTs appears to protect phospholipids from being removed from the droplet surface by bile salt micelles. The affinity of pancreatic lipase for the emulsions was comparable, and calcium ions were shown to play a key role in suppressing the lag phase in a surface area-dependent manner. The enzyme velocity was inversely related to the mean particle size of the emulsions. Pure MCTs were hydrolyzed faster than pure LCTs. With comparable sizes, a mixed MCT/LCT emulsion was hydrolyzed more slowly than a pure MCT emulsion. In conclusion, varying the mean droplet size or the triglyceride composition of emulsions affects their hydrolysis rate catalyzed by pancreatic lipase. The present findings could help in preparing new emulsions for enteral feeding, especially for patients with a reduced digestive capacity.