Food grade duplex emulsions designed and stabilised with different osmotic pressures

In this study we have investigated the production of food grade W-1/O/W-2 duplex emulsions with salt partitioned into one water phase but not the other. Investigations were carried out with and without balancing osmotic pressures with glucose. A stable 30% primary W-1/O emulsions containing salt could be produced with more than or equal to 2% polyglycerol polyricinoleate (PGPR) in the oil phase. We suggest that the addition of salt strengthens the interactions between surfactant molecules in the adsorbed film. This is supported by interfacial viscosity and elasticity measurements both of which increased on addition of salt and the fact that in the presence of salt the emulsion was more stable. These simple emulsions were then processed to construct duplex emulsions. When osmotic pressures were balanced with glucose there was still a release of salt in storage. The extent and rate of release was proportional to glucose concentration. This effect was followed over a period of 60 days. These data suggest that the release is driven by the chemical potential difference between the two water compartments rather than the unbalanced osmotic pressures. These observations are explained in the context of a water structuring effect from the added glucose, which lowers the interfacial tension of oil-water interface and thus facilitates micellar transport of hydrated salt ions across the oil layer. (C) 2010 Elsevier Inc. All rights reserved.