Effect of gelation of inner dispersed phase on stability of (w1/o/w2) multiple emulsions

• Non-gelled multiple emulsions have reasonable yield and processing stability.
• High yields of multiple emulsions with gelled w1 phase.
• Yield depends on type of gelling agent used.
• Yield also depends on fracture stress of inner droplets.
• Yield, oil droplet size and fracture stress of inner droplets are correlated.

The use of water-in-oil-in-water (w1/o/w2) multiple emulsions offers a method for the reduction of oil in foods. In this study we investigated the influence of osmotic pressure tailoring and gelation of the inner dispersed w1 water droplets on the stability and yield of multiple emulsions. Yield is defined as the percentage of water retained in the inner dispersed phase w1 after preparation, storage, heat or shear treatment. Differential scanning calorimetry (DSC) was used to determine the yield. Gelation of the inner aqueous phase w1 by gelatin or whey protein isolate increased stability and yield of multiple emulsions after preparation, storage (after 7 days at 20 °C), shear (5 min at 10,000 rpm) and heat treatment (30 min at 97 °C) by 20%–50% compared to reference emulsions. Yield and emulsion stability were correlated to oil droplet sizes and the mechanical properties of the gelled inner dispersed droplets. Yield increased with increasing fracture stress and modulus of gelled w1 droplets. We conclude from the present study that stable food-grade multiple (w1/o/w2) emulsions can be prepared by gelling the inner dispersed phase. These multiple emulsions are able to withstand shear and heat treatments. This provides opportunities to use these emulsions as potential fat replacers in foods.

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