Effect of Tween Emulsifiers on the Shear Stability of Partially Crystalline Oil-in-Water Emulsions Stabilized By Sodium Caseinate

We investigated the effects of Tween emulsifier fatty acid chain length on the shear stability and crystallization behavior of 35 wt% partially crystalline oil-in-water emulsions prepared with and without 1 wt% sodium caseinate. Emulsions containing sodium caseinate and Tween 20, 40, 60 or 80 varied in shear stability, degree of supercooling and crystallization behavior depending on the type and concentration of Tween as well as the presence of protein. Generally, emulsions containing the unsaturated emulsifier Tween 80 were the most shear sensitive followed by the saturated emulsifiers Tween 20, 40 and 60 in order of increasing fatty acid chain length. Long chain saturated Tween emulsifiers (40 and 60) improved shear stability regardless of whether sodium caseinate was present indicating that alone, these emulsifiers form more robust interfacial films compared to the saturated short chain length Tween 20 and Tween 80. In emulsions prepared with sodium caseinate, the degree of supercooling decreased and the crystallization rate diminished with increasing saturated fatty acid chain length but only negligible changes were found without sodium caseinate. Together, these findings indicate that long chain saturated Tween emulsifiers provide better emulsion stability regardless of the presence of sodium caseinate but with sodium caseinate, stability may also be affected by changes to fat crystallization. These novel findings provide guidance on how combinations of proteins and emulsifiers can be used to modify and control the stability of partially crystalline oil-in-water emulsions through their combined effects on the properties of the interfacial film and fat crystallization.