Natural encapsulation systems possess unique structural and compositional properties that could potentially improve the physicochemical stability and bioaccessibility of encapsulates. This research was aimed at evaluating the potential of milk fat globules (MFGs) as a model natural carrier system for the encapsulation and stability of diverse lipid soluble compounds. The specific objectives of this work were to: (a) evaluate the role of compound’s molecular properties (i.e. octanol/water partitioning coefficient (log P) and topological polar surface area (TPSA)) and well as process parameter such as time and temperature on the encapsulation of lipid-soluble bioactives; (b) evaluate the in vitro gastric stability of a model bioactive compound encapsulated in MFGs; (c) characterize in vitro gastrointestinal release of a model bioactive compound; and (d) develop electron paramagnetic resonance spectroscopy (EPR) approach to study real time dynamics of MFGs interfacial structure.
In this research, MFGs isolated from raw milk were used to encapsulate a range of lipid-soluble compounds via simple non-thermal diffusion process. To evaluate the influence of compound’s degree of hydrophobicity, bioactive compounds with log P ranging between 1.5 and 8 were tested. Additionally, process parameter such as time, temperature, compound concentration, and carrier solvent concentration effects were evaluated. Findings of this study showed: (a) a positive effect associated with increased concentrations of carrier solvent and incubation temperature, (b) limited effect of prolonged incubation time beyond 40 min, (c) log P and TPSA could be used for predicting the partitioning behavior of lipid-soluble bioactives in MFGs structure. Overall, increase in log P was associated with an increase in encapsulation efficiency, and decrease of TPSA values was associated with preferential deposition of the selected compounds at the MFGs interface.
To assess the gastric stability of MFGs encapsulated compounds, vitamin D3 encapsulated in bovine MFGs was subjected to in vitro gastric digestion and its stability was evaluated using LC-MS methodology. Encapsulated vitamin D3 demonstrated stability and resistance to isomerization for up to 2 h.
In vitro gastrointestinal release of the model bioactive compound curcumin was used to evaluate the release properties of MFGs, and study the physical stability of MFGs based on particle size measurements and fluorescence imaging. No significant release of encapsulated curcumin was achieved in the gastric phase, while rapid and extensive release was recorded in the intestinal phase (>80% curcumin released in 3 h). These results were related to fluorescence images of MFGs and particle size measurements. These measurements illustrated limited morphological changes in MFGs structure in the gastric phase, while significant structural changes were observed in the intestinal phase.
To better understand the interfacial events that occur during intestinal lipid digestion, an EPR approach was developed to study real time dynamics of MFGs interfacial structure. Results of this study correlated changes in MFGs membrane fluidity and interfacial events associated with bile salts and pancreatic lipase adsorption and interaction with MFGs interface. Interactions of MFG interface with bile salts resulted in instantaneous displacement of EPR-probed membrane components and reduced fluidity of the probed membrane. On the other hand, pancreatic lipase caused an increase in measured fluidity due to its ability to adsorb and disrupt interfaces.
Overall, results of this research demonstrated that a wide range of lipid-soluble bioactive compounds could be encapsulated in MFGs using a simple, rapid, and low energy process. Future research focused on creating and optimizing MFGs-based food and pharmaceutical ingredients.
|Commitee:||Taha, Ameer, Voss, John|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||DAI-B 81/2(E), Dissertation Abstracts International|
|Subjects:||Food Science, Biochemistry|
|Keywords:||Encapsulation, In vitro release, Milk fat globules|
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