Development of multiple emulsions based on the repulsive interaction between sodium caseinate and LBG

The stability of oil-in-water, water-in-water and multiple emulsions containing sodium caseinate (Na-CN) and/or locust bean gum (LBG) at pH 5.5 was investigated with different compositions using a visual analysis (creaming and/or phase separation), optical microscopy and rheological measurements. Oil-in-water emulsions (O/W) were produced by high pressure homogenization, which promoted the formation of very small droplets (∼0.4 μm) and hindered the destabilization process. In the second step of this study, a visual phase diagram was constructed in order to identify the concentrations of sodium caseinate (Na-CN) and locust bean gum (LBG) that led to phase separation at pH 5.5. A mixed solution composed of 3% (w/v) Na-CN and 0.3% (w/v) LBG was chosen to produce the water-in-water and multiple emulsions. After centrifugation, the solution was separated into an upper phase rich in polysaccharide (PS) and a bottom phase rich in protein (PR), which were mixed in different proportions (1:3, 1:1, 3:1), forming the water-in-water (W/W) emulsions. The stability, microstructure and rheological properties of the W/W emulsions depended strongly on the composition of the biopolymers. An increase in the polysaccharide concentration in the W/W emulsions led to the production of more viscous and stable systems. Multiple emulsions with different characteristics were prepared and also depended on the biopolymer composition. The system with the highest polysaccharide content was the only one that showed an O/W/W structure, while the others presented the microstructure of an O/W-W/W emulsion.

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► Mixture of Na-CN around pI with a neutral polysaccharide (LBG) formed W/W emulsions.
► Low-fat multiple emulsions were made from W/W and Na-CN-stabilized O/W emulsions.
► The volume fraction of ingredients on the systems determined their microstructures.
► Biopolymer composition determined the type of multiple emulsion (O/W-W/W or O/W/W).