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Encapsulation of Bioactive Compounds in Liposomes prepared with Milk Fat Globule Membrane-Derived Phospholipids

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Title: Encapsulation of Bioactive Compounds in Liposomes prepared with Milk Fat Globule Membrane-Derived Phospholipids
Author: Farhang, Bita
Department: Department of Food Science
Program: Food Science
Advisor: Kakuda, Yukio
Abstract: Liposome technology is considered to be an effective technology for the encapsulation and controlled release of nutraceuticals and bioactive compounds, as well as for enhancing their stability and bioavailability. This research focused on liposomes prepared from milk phospholipids. Model hydrophobic and hydrophilic compounds, namely β-carotene and ascorbic acid were incorporated in the liposomes and their properties studied. Liposomes prepared by microfluidization with milk phospholipids showed an apparent diameter of about 100 nm, but in the presence of hydrophobic compounds, they were larger. The incorporation efficiencies for ascorbic acid increased as the concentration of phospholipid-rich powder increased from 5% to 10% (w/w). However, from 10% to 16% (w/w), the incorporation efficiency reached a plateau value of 26%. There appeared to be a change in liposome structure from unilamellar to multivesicular/multilamellar vesicles with high levels of phospholipids (16%) and a high number of passes through the microfluidizer. Storage studies showed less stable dispersions when stored at pH 3 compared to pH 7. The incorporation of hydrophobic compounds was investigated using heat, ethanol and chloroform methods. High incorporation efficiencies of β-carotene were obtained in all cases, i.e. 91 % for the heat and ethanol methods and 98 % for the chloroform method. No significant differences were observed in the encapsulation efficiency (26%± 0.5) of ascorbic acid. The liposomes made using chloroform to dissolve -carotene were significantly smaller in size (120±2 nm) compared to those prepared using the heat or ethanol (approximately 175 nm) methods; however with all treatments, after one day of storage at 4°C, the liposome dispersion showed phase separation. This occurred not only with β-carotene but also with other hydrophobic compounds, namely, coenzyme Q10 and Vitamin D3, and it was concluded that when hydrophobic compounds are incorporated within the unilamellar membrane of the liposomes, the vesicles become colloidally unstable. The instability was resolved by preparing liposomes containing hydrophobic compounds and covering them with a secondary layer of phospholipids, using a secondary homogenization process. As more information becomes available on the health benefits associated with the consumption of milk derived phospholipids, there will be an ever increasing need to design solvent free phospholipid vesicles for incorporation into foods.
Date: 2013-01
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