Effect of the size and interface composition of milk fat globules on their in vitro digestion by the human pancreatic lipase: Native versus homogenized milk fat globules
Résumé
Although the bioavailability of dietary lipids is of primary importance in human nutrition and health, the mechanisms involved in lipid digestion are not fully understood and are of growing interest. The objective of this study was to determine the effect of the size of milk fat globules and of the composition of their interface on the activity of the human pancreatic lipase (PL). Native milk fat globules of various sizes covered by their biological membrane (MFGM) and homogenized fat globules of various sizes covered by milk proteins were prepared from whole milk and underwent lipolysis by the human PL with colipase and bile salts. A lag phase preceding the hydrolysis of milk TAG occurred with all native milk fat globules samples but not with homogenized milk samples. The kinetic parameters of human PL were determined by measuring the enzyme activity either after the lag phase for native milk fat globules samples or immediately after the addition of the enzyme for homogenized milk samples. The catalytic efficiency of human PL is 4.6-fold higher on small (1.8 mm) than large (6.7 mm) native milk fat globules, related to a 3.6-fold larger available surface. Despite the 25-fold larger available surface, milk TAG from homogenized milk are only 2-fold better hydrolyzed compared to native milk fat globules, as a possible result of a less favourable interface covered by milk proteins. The potential mechanisms involved in native vs. homogenized milk fat globules digestion by the human PL are discussed. Our study highlights the crucial role of the MFGM in the efficient digestion of milk fat globules and brings new insight for the design of dairy products and infant formulas.