29B-31 |
Production and characterization of O/W emulsions containing multi-layered droplets stabilized by b-lactoglobulin-pectin membranes |
L. Moreau, H. J. KIM, E. A. Decker, and D. J. McClements. Dept. of Food Science, Univ. of Massachusetts, Amherst, Chenoweth Lab., Box 31410, Amherst, MA 01003-1410 Many food emulsions are subjected to environmental conditions that promote instability, such as elevated temperatures, 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. We intended to create oil-in-water emulsions with improved stability by combining the beneficial attributes of different kinds of emulsifiers to form multi-layered membranes around the oil droplets. Oil-in-water emulsions containing multi-layered droplets stabilized by b-lactoglubulin(b-Lg)-pectin membranes were produced using a two-stage process. A primary emulsion was prepared by homogenizing 10 wt% corn oil with 90 wt% aqueous solution (1 wt% b-Lg, 5 mM imidazole/acetate buffer, pH 3.0) using a high pressure valve homogenizer. Secondary emulsions with varying compositions were produced by diluting this emulsion with aqueous pectin solution (5 wt% corn oil, 0.5 wt% b-Lg, 5 mM imidazole/acetate buffer, 0 to 0.22 wt% pectin, pH 3.0). The electrical charge on the droplets decreased from +33 to -19 mV as the pectin concentration was increased from 0 to 0.22 wt%, which indicated that pectin adsorbed to droplet surfaces. The mean particle diameter of the emulsions increased dramatically and the emulsions became unstable to creaming when the pectin concentration exceeded 0.06 wt%, which was attributed to charge neutralization and bridging flocculation effects. Secondary emulsions with relatively small droplet diameters (»1.2 mm) could be produced by disrupting flocs formed in emulsions containing droplets with high negative charges, e.g., by sonication, blending or homogenization. These emulsions had good stability to droplet aggregation at high ionic strength (£ 500mM NaCl) and low pH (pH 3). The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved stability to environmental stresses, e.g., heating, freeze-thaw cycling.
Session 29B, Food Chemistry: Lipids, antioxidants and emulsifiers
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