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

Abstract

A three step process, based on electrostatic layer-by-layer deposition, was used to produce oil-in-water emulsions containing submicron ( d 32≈0.3 μm) 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 ( ζ≈−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 ( ζ≈+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 ( ζ≈−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 (≤500 mM NaCl), thermal treatments (30–90 °C for 20 min) and freeze–thaw cycling (−20 °C for 22 h/30 °C 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.