Multiple Emulsions – Preparation and Stability

Multiple emulsions (W1/O/W2) with a long-term stability of at least 12 months were prepared in order to encapsulate low molecular weight bioactive substances (Mr < 2000 g/mol). The influence of the emulsifying procedure, i.e. the variation in energy input for dispersing W1/O in W2, and the influence of the emulsion composition were investigated in relation to emulsion stability and encapsulation efficiency. In order to incorporate the W1/O into the W2 phase membrane emulsification, or low pressure emulsification, using a special orifice valve is favourable. A satisfactory coalescence stability of multiple emulsions with small oil droplets can be achieved by using proteins as O/W emulsifiers instead of low molecular weight emulsifiers. For good emulsion stability and low leakage from the inner to the outer water phase, an osmotic gradient (~ 180-200 mOsmol/kg) between W1 and W2 is necessary. Long-term stable multiple emulsions enriched with bioactive or flavouring substances can be prepared with low and high dry matter in both aqueous phases by adding different carbohydrates. The stability and release properties can be tailored by varying the oil phase or by modifying the O/W interface. PC depleted lecithin proved to be a suitable substitute for PGPR as an emulsifier for the effective dispersal of the W1 phase into the oil phase. Therefore, multiple emulsions offer the opportunity to enclose nutritional components for multidispersed functional foods.