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

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• 作者：Tomohito Hanazawa ; Brent S. Murray
• 刊名：Langmuir
• 出版年：2013
• 出版时间：August 6, 2013
• 年：2013
• 卷：29
• 期：31
• 页码：9841-9848
• 全文大小：394K
• 年卷期：v.29,no.31(August 6, 2013)
• ISSN：1520-5827

文摘

The phase separation of a model system consisting of sodium caseinate + xanthan 卤 a low fraction (up to 3 wt %) of an oil-in-water emulsion was studied at room temperature (20鈥?5 掳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 鈥渆mulsions鈥?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 (畏_i) between two macroscopically separated phases was also measured. In the presence of the semisolid mixed droplets 畏_i = 25 mN s m^鈥?, significantly higher than 畏_i with the pure (liquid) TD droplets (15 mN s m^鈥?) or with the pure solid EC droplets (12 mN s m^鈥?) or in the absence of droplets (<3 mN s m^鈥?). Confocal microscopy showed that the microstructure of the phase separating regions also depended upon the composition of the oil droplets, and it is tentatively suggested that the more marked effects of the mixed emulsion droplets were due to them forming a stronger network at the interface via partial coalescence. Control of the extent of interfacial aggregation of droplets is therefore possibly one way to influence the course of phase separation in biopolymer mixtures.