Effect of Oil Droplets and Their Solid/Liquid Composition on the Phase Separation of Protein–Polysaccharide Mixtures

• Published in: Langmuir 2013-08, Vol.29 (31), p.9841-9848
• Main Authors: Hanazawa, Tomohito, Murray, Brent S
• Format: Article
• Language: English
• Subjects: Alkanes - chemistry; Calcium Chloride - chemistry; Chemistry; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Oils - chemistry; Particle Size; Polysaccharides - chemistry; Proteins - chemistry; Surface Properties
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la401595u

The phase separation of a model system consisting of sodium caseinate + xanthan ± a low fraction (up to 3 wt %) of an oil-in-water emulsion was studied at room temperature (20–25 °C). The composition of the oil phase was either 100 wt % n-tetradecane (TD); 50% TD + 50% eicosane (EC) or 100% EC. The droplets in these three “emulsions” were therefore totally liquid, partially solid, and totally solid, respectively. In the presence of 22 mM CaCl2, the mixed TD+EC droplets were most effective at inhibiting phase separation, while the EC emulsions could not prevent phase separation at all. At 32 mM CaCl2 the emulsions tended to promote phase separation, possibly due to enhanced calcium ion-induced droplet aggregation. The apparent interfacial viscosity (ηi) between two macroscopically separated phases was also measured. In the presence of the semisolid mixed droplets ηi = 25 mN s m–1, significantly higher than ηi with the pure (liquid) TD droplets (15 mN s m–1) or with the pure solid EC droplets (12 mN s m–1) or in the absence of droplets (