Real-time measurements of milk fat globule membrane modulation during simulated intestinal digestion using electron paramagnetic resonance spectroscopy.

Milk Fat Globules with their unique interfacial structure and membrane composition are a key nutritional source for mammalian infants, however, there is a limited understanding of the dynamics of fat digestion in these structures. Lipid digestion is an interfacial process involving interactions of enzymes and bile salts with the interface of suspended lipid droplets in an aqueous environment. In this study, we have developed an electron paramagnetic resonance spectroscopy approach to evaluate real time dynamics of milk fat globules interfacial structure during simulated intestinal digestion. To measure these dynamics, natural milk fat globule membrane was labeled with EPR-active probe, partitioning of EPR probes into MFGs membrane was validated using saturation-recovery measurements and calculation of the depth parameter Φ. After validation, the selected spin probe was used to evaluate the membrane's fluidity as a measure of the interface's modulation in the presence of bile salts and pancreatic lipase. Independently, bile salts were found to have a rigidifying effect on the spin probed MFGM, while pancreatic lipase resulted in an increase in membrane fluidity. When combined, the effect of lipase appears to be diminished in the presence of bile salts. These results indicate the efficacy of EPR in providing an insight into small time scale molecular dynamics of phospholipid interfaces in milk fat globules. Understanding interfacial dynamics of naturally occurring complex structures can significantly aid in understanding the role of interfacial composition and structural complexity in delivery of nutrients during digestion.

Encapsulation and release of curcumin using an intact milk fat globule delivery system.

The stability and dispersibility of lipid-soluble bioactives in food systems are often modified via encapsulation in oil in water emulsions and lipid or protein-based nanoparticles. These encapsulation approaches frequently require the addition of surfactants/emulsifiers, sacrificial antioxidants, and high-energy methods to create the dispersed phase and stabilize encapsulated compounds. In contrast to conventional encapsulation approaches, this study evaluates pre-formed and naturally occurring lipid structures, milk fat globules (MFGs), for the encapsulation of a model lipid-soluble bioactive, curcumin. Intact MFGs were separated from raw milk and dispersed in water, and then curcumin was added in the presence of ethanol. Partitioning of curcumin to the lipid core of MFGs was confirmed using fluorescence imaging. The encapsulation efficiency and loading capacity of curcumin were measured. 1186.65 ± 14.63 µg of curcumin were encapsulated per gram of milk fat, in the presence of 10% v/v of ethanol with an encapsulation efficiency ranging between 59 and 64%. The study also evaluates the release of curcumin from MFG carriers under simulated gastrointestinal conditions, and correlates the release with morphological changes in milk fat globules during digestion. The results show limited release of encapsulated curcumin in the gastric phase (∼27%), and substantial release in the intestinal phase (>80%). Regarding their morphology, MFGs showed little changes in the gastric phase, and significant changes in the intestinal phase. Overall, the results of this study demonstrate encapsulation of a lipid-soluble bioactive compound in naturally occurring MFGs using a simple, rapid, and low-energy alternative to conventional encapsulation systems.