Macro- vs. micromolecular stabilisation of W/O/W-emulsions

• The stability of W/O/W-emulsions was investigated.
• Use of a small molecular surfactant or a high molecular weight hydrophilic emulsifier.
• Different release patterns involved for the two different DEs.
• A gelled W/O/W emulsion were successfully prepared.
• Gelatin based DE less influenced by variation in PGPR.

Water-in-Oil-in-Water (W/O/W) double emulsions (DEs) were prepared with high molecular weight gelatin as hydrophilic emulsifier and gelling agent of the external water phase and their stability was compared to DEs prepared with the hydrophilic emulsifier polysorbate 80. The Water-in-Oil (W/O)-emulsions were prepared with corn oil and polyglycerol polyricinoleate (PGPR) as the lipophilic emulsifier. Tartrazine, a synthetic dye, was added to the inner water phase and the encapsulation efficiency of the marker was measured. A gelled DE was successfully obtained and its rheological properties were possible to adjust without affecting the DE stability to a large degree. During a 90-days stability study, DEs stabilised by gelatin showed a high initial encapsulation yield (98.5–96.5%), with no further release of tartrazine measured after the first day.Release of tartrazine was observed from the DEs prepared with polysorbate 80 during the first days after preparation, whereafter no further release was observed for the remaining 90 days period. Contrary to the DEs stabilised by gelatin, the encapsulation efficiency of tartrazine was highly dependent on the concentration of PGPR. By addition of a counter solute (NaCl) into the external water phase, osmotically adjusted DEs (Δ −0.14, −0.07, 0.00 and 0.14 Osm) were prepared for the polysorbate 80 stabilised W/O/W-emulsion. Higher encapsulation yields were obtained with increasing amounts of NaCl, with the highest amount of tartrazine retained for the hyperosmotic DE (Δ 0.14 Osm) formulation.

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