46C-15 |
Utilization of lecithin-chitosan membranes to improve stability of food emulsions |
S. OGAWA1, E. A. Decker, and D. J. McClements. (1) Department of Food Science, University of Massachusetts, Chenoweth Laboratory, Amherst, MA 01003 Many food emulsions are subjected to environmental conditions that promote instability, such as elevated temperatures, freeze-thaw cycling, high mineral contents and mechanical agitation. There is currently a lack of natural emulsifiers available for creating food emulsions that can withstand these harsh conditions. Our objective was to develop a novel emulsifier technology to improve food emulsion stability. An anionic surfactant (lecithin) that rapidly adsorbs to the surface of lipid droplets during homogenization was used to produce a primary emulsion with small droplet sizes, then an oppositely charged biopolymer (chitosan) was added to the system to produce secondary emulsions containing droplets coated with a lecithin-chitosan membrane. A primary emulsion was prepared by homogenizing 5 wt% corn oil with 95 wt% aqueous solution (1 wt% lecithin, 100 mM acetic acid, pH 3.0) using a high pressure valve homogenizer. A series of secondary emulsions was prepared by diluting the primary emulsion with aqueous chitosan solutions to form samples with the following compositions: 1 wt% corn oil, 0.2 wt% lecithin, and 0 to 0.04 wt% chitosan. The particle size distribution, particle charge and creaming stability of the emulsions was then measured. The electrical charge on the droplets increased from -49 to +54 mV as the chitosan concentration was increased from 0 to 0.04 wt%, which indicated that chitosan adsorbed to the surface of the droplets. The mean particle diameter in the emulsions increased dramatically and the emulsions became unstable to creaming when the chitosan concentration exceeded 0.008 wt%, which was attributed to charge neutralization and bridging flocculation effects. However, stable emulsions with small droplet sizes could be produced by sonicating emulsions containing lecithin-chitosan stabilized droplets with high positive charges. The interfacial engineering technology developed in this study could lead to the creation of food emulsions with greatly improved stability to environmental stresses.
Session 46C, Food Chemistry: Lipids, antioxidants and emulsifiers
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