The purpose of this study was to investigate the effects of three anionic polysaccharides (low methoxyl pectin (LMP), high methoxyl pectin (HMP) and alginate) on the physicochemical properties and stability of lactoferrin (LF)-coated lipid droplets. LMP, HMP and alginate were shown to adsorb to the surfaces of LF-coated droplets at neutral pH, which was primarily attributed to electrostatic attraction between anionic groups on the polysaccharide molecules and cationic patches on the protein surfaces. In the absence of polysaccharide, the LF-coated droplets were highly unstable to aggregation when heated above about 60 degrees C at pH 7, presumably because thermal denaturation of the adsorbed proteins increased droplet attraction. The addition of either LMP or HMP prior to heating greatly improved the thermal stability of the emulsions, with no aggregation being observed from 30 to 90 degrees C. On the other hand, the presence of anionic polysaccharides had little effect on emulsion stability or even promoted emulsion instability when 0 to 200 mM NaCl or CaCl2 was added. This study shows that the stability of LF-coated lipid droplets can be improved by careful selection of an appropriate type and amount of anionic polysaccharide to incorporate.
Multilayer emulsions containing lipid droplets coated by lactoferrin (LF) - anionic polysaccharide layers have improved resistance to environmental stresses (such as pH, salt, and temperature), but their behavior within the gastrointestinal tract (GIT) is currently unknown. The objective of this research was therefore to monitor changes in the physicochemical properties and digestibility of these systems under simulated GIT conditions. Primary emulsions (5% corn oil, 0.5% LF) were prepared using a high-pressure homogenizer. Secondary emulsions (5% corn oil, 0.5% LF, 0.5% polysaccharide) were prepared by incorporating alginate, low methoxyl pectin (LMP) or high methoxyl pectin (HMP) into primary emulsions. Emulsions were then subjected to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) conditions in sequence. LF, LF-LMP and LF-HMP emulsions were stable to droplet aggregation in the stomach but aggregated in the small intestine, whereas LF-alginate emulsions aggregated in both the stomach and small intestine. The presence of a dietary fiber coating around the initial lipid droplets had little influence on the total extent of lipid digestion in SIF, but LF-alginate emulsions had a slower initial digestion rate than the other emulsions. These results suggest that the dietary fiber coatings may become detached in the small intestine, or that they were permeable to digestive enzymes. Pepsin was found to have little influence on the physical stability or digestibility of the emulsions. The knowledge obtained from this study is important for the design of delivery systems for encapsulation and release of lipophilic bioactive ingredients.
Nanolaminated protein coatings may be useful for stabilizing encapsulated lipids in functional food and pharmaceutical products during storage, but releasing them after ingestion. Protein coatings had little impact on triglyceride digestion, but they greatly reduced β-carotene bioaccessibility, possibly due to binding to lactoferrin.
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