Influence of environmental stresses on stability of O/W emulsions containing droplets stabilized by multilayered membranes produced by a layer-by-layer electrostatic deposition technique

A three step process, based on electrostatic layer-by-layer deposition, was used to produce oil-in-water emulsions containing submicron (d(32) approximate to 0.3 mum) oil droplets stabilized by sodium dodecyl sulfate (SDS)-chitosan-pectin membranes (100 mM acetic acid, pH 3.0). First, primary emulsions (5 wt% corn oil, 5 mM SDS) containing anionic droplets (zeta approximate to -60 mV) stabilized by SDS membranes were prepared using a high-pressure value homogenizer. Second, secondary emulsions (1 wt% corn oil, 1 mM SDS, 0.024 wt% chitosan) containing cationic droplets (zeta approximate to +59 mV) stabilized by SDS-chitosan membranes were formed by diluting the primary emulsion with aqueous chitosan solution and agitating to disrupt any flocs. Third, tertiary emulsions (0.2 wt% corn oil, 0.2 mM SDS, 0.0048 wt% chitosan, 0.040 wt% pectin) containing anionic droplets (zeta approximate to -14 mV) stabilized by SDS-chitosan-pectin membranes were formed by diluting the secondary emulsion with aqueous pectin solution. The stability of primary, secondary and tertiary emulsions to pH, ionic strength, thermal processing and freeze-thaw cycling were determined. The droplets in tertiary emulsions had good stability to droplet aggregation over a wide range of pH values (pH 3.0-8.0), NaCl concentrations (less than or equal to 500 mM NaCl), thermal treatments (30-90 degreesC for 20 min) and freeze-thaw cycling (-20 degreesC for 22 h/30 degreesC for 2 h). The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to environmental stresses. (C) 2004 Elsevier Ltd. All rights reserved.