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Date of Award
Doctor of Philosophy (PhD)
David J. McClements
Eric A. Decker
The aim of this thesis was to develop and test novel food-grade nanodispersions, such as nanoemulsions and solid lipid nanoparticles, for the encapsulation, protection and delivery of bioactive lipophilic food components. Initially, the impact of system composition and homogenization conditions on the formation of nanoemulsions using a high pressure homogenizer (microfluidizer) was examined. The mean particle diameter decreased with increasing homogenization pressure and number of passes, with a linear log-log relationship between mean particle diameter and homogenization pressure. Surfactants emulsifiers formed smaller droplets than protein emulsifiers, which was attributed to their ability to rapidly adsorb to the droplet surfaces during homogenization. At low oil phase-to-aqueous phase viscosity ratios, much smaller mean droplet diameters could be achieved for SDS ( d ∼ 60 nm) than for β-lactoglobulin ( d ∼ 150 nm).
The effectiveness of various biopolymer emulsifiers at forming and stabilizing model beverage emulsions was examined: β-lactoglobulin (BLG); gum arabic (GA); modified starch (MS). Orange oil-in-water nanoemulsions (5% oil) were prepared using high pressure homogenization. Extensive droplet aggregation occurred in BLG-stabilized nanoemulsions around their isoelectric point, at high salt concentrations, and at high temperatures, due to changes in electrostatic and hydrophobic interactions. There was little effect of pH, ionic strength, and temperature on emulsions stabilized by GA or MS, due to strong steric (rather than electrostatic) stabilization.
The potential of utilizing oil-in-water (O/W) nanoemulsions stabilized by a globular protein (β-lactoglobulin) for encapsulating and protecting β-carotene was examined. The influence of temperature, pH, ionic strength, and emulsifier type on the physical and chemical stability of β-carotene enriched nanoemulsions was investigated. The rate of color fading due to β-carotene degradation increased with increasing storage temperature (5 to 55 oC), decreasing pH, and was largely independent of ionic strength (0 to 500 mM of NaCl). β-carotene degradation was considerably slower in β-lactoglobulin-stabilized nanoemulsions than in Tween 20-stabilized ones. The rate of β-carotene degradation decreased upon addition of additional antioxidants. EDTA was found more effective than ascorbic acid, and Coenzyme Q10 was more effective than vitamin E acetate. The utilization of water-soluble and oil-soluble antioxidants in combination (EDTA and vitamin E acetate) was less effective than using them individually.
Solid lipid nanoparticles (SLN) were prepared by homogenizing at a temperature ([approximate] 80°C) exceeding the melting point of the lipid phase (tripalmitin), and then cooling the resulting oil-in-water nanoemulsions to induce lipid droplet crystallization. Blending tripalmitin with low melting point lipids (either medium chain triglycerides or orange oil) prior to homogenization led to a considerable alteration in the phase behavior and stability of SLN. The presence of the carrier oils reduced the crystallization temperature, melting temperature, and melting enthalpy of tripalmitin.
The bioaccessibility of β-carotene encapsulated within nanoemulsion-based delivery systems was examined. A non-ionic surfactant (Tween 20) was used as an emulsifier and long chain triglycerides (LCT), medium chain triglycerides (MCT) or orange oil were used as carrier oils. The bioaccessibility of β-carotene was negligible ([approximate] 0%) in orange oil nanoemulsions because no mixed micelles were formed to solubilize β-carotene, and was relatively low ([approximate] 2%) in MCT nanoemulsions because the mixed micelles formed were too small to solubilize β-carotene. In contrast, β-carotene bioaccessibility was relatively high (about 66%) in LCT nanoemulsions because the mixed micelles were large enough to solubilize the bioactive molecule.
Overall, our results have important implications for the design of effective delivery systems for encapsulation of carotenoids and other lipophilic bioactive components so that they can be incorporated into functional food and beverage products.
Qian, Cheng, "Food-Grade Nanodispersions For Encapsulation, Protection and Delivery Of Bioactive Food Component" (2013). Doctoral Dissertations 1896 - February 2014. 438.