Interactions between Soy Lysophospholipid and Sodium Caseinate and Their Influence on W/O Emulsion

Abstract

Competitive adsorption on air/water surface was investigated in a sodium caseinate/surfactant system. Surface tension data on caseinate/surfactant mixtures gave information on their interactions. The values of surface tension were measured for soy lysophosphatidylcholine (SLPC), SLPC/fatty acid (FA) mixtures, soy lysophospholipid (SLP), sucrose mono-distearate (SE) and SLP/SE mixture as a function of surfactant concentration in the presence or absence of caseinate. SE and SLPC which is neutral lipid had no interaction with the protein. On the other hand, SLP and equimolar mixtures of SLPC/FA interacted strongly with the protein, both at the interface and in bulk solution, and it was suggested that electrostatic complex formation might have occurred. SLP was added to SE for the preparation of O/W emulsions containing caseinate. The addition of SLP improved quality and stability of the emulsions. It seems that the protein/SLP complex molecules attach tightly to the droplets and stabilize the emulsions, whereas the stability of emulsion prepared with the same amount of LPC was poor. Therefore, it is suggested that the protein moleculs are displaced from the droplet surface by the action of excessive surfactant.