Utilization of interfacial engineering to improve food emulsion properties
Abstract (Summary)The Layer by layer electrostatic deposition (LBL) technique has been shown to have potential applications in foods such as controlled/triggered release, prevention of lipid oxidation and stabilization of emulsions to processing and storage conditions. Biopolymer properties (e.g. , as charge density, molecular weight and conformation) and droplet properties ( e.g. , concentration, size and charge) are the most important factors in the production of stable multilayered emulsions using this technique. In this study all natural biopolymers, Ã?Â²-lactoglobulin (Blg), pectin and chitosan have been used to produce multilayer-coated O/W emulsions. Blg was used to produce a primary emulsion with small droplet sizes, then, an anionic biopolymer (pectin) was added to the system to produce secondary emulsions containing droplets coated with an emulsifier-biopolymer (Blg-pectin) layer. The effect of preparation pH, presence or absence of NaCl, and thermal treatment was studied. It was found that mixing the droplets and biopolymer at a pH where they initially had similar charges (pH 7) and then adjusting the pH to values where they had opposite charges (pH 3-4) led to the formation of more stable secondary emulsions than directly mixing the droplets and biopolymer at pH values where they had opposite charges. The Blg-pectin coated droplets in the secondary emulsions were stable to droplet aggregation and creaming at temperatures up to 90Ã?Â°C and NaCl concentrations up to 300 mM. The interaction of Blg and chitosan as a function of pH and chitosan concentration was examined with the expectation of drawing conclusions for their interaction at emulsion droplet surfaces. Chitosan interacted with Blg exothermically to form either soluble or insoluble complexes depending on the pH. At pH values where chitosan and Blg have opposite charges (pH 6 and 7) they interact strongly with each other to form insoluble complexes. Stable Blg/chitosan secondary emulsions however could not be produced due to the narrow range of chitosan concentration (between saturation and depletion concentrations) where this could be achieved. Stability maps are suggested as a strategy to predict areas of possible multilayer formation based on preparation conditions and polyelectrolyte and droplet characteristics. Blg-pectin-chitosan tertiary emulsions were also prepared and found to be stable over a wider range of pH (3-6) which was attributed to the ability of the multi-layered interfaces to either increase the repulsive interactions between the droplets (e.g., steric and electrostatic), decrease the attractive interactions (e.g. , van der Waals), and/or to increase the resistance of the interfacial layer to rupture. This study provides valuable information on use of the LBL technique in the area of multilayered food emulsions with a focus on the effects of preparation conditions and biopolymer characteristics on stable emulsion formation and long term stability. Better understanding of these systems provided here may lead to applications in the area of encapsulation and delivery of sensitive active ingredients.
School Location:USA - Massachusetts
Source Type:Master's Thesis
Date of Publication:01/01/2006