Milk Science Research Institute, Megmilk Snow Brand Co., Ltd., 1-1-2, Minamidai, Kawagoe, Saitama, 350-1165, Japan.
Langmuir. 2013 Aug 6;29(31):9841-8. doi: 10.1021/la401595u. Epub 2013 Jul 24.
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 (<3 mN s m(-1)). 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.
在室温（20-25°C）下，研究了由酪蛋白酸钠+黄原胶组成的模型体系的相分离，其中含有低浓度（高达 3wt%）的水包油乳液。油相的组成为 100wt%正十四烷（TD）；50%TD+50%二十烷（EC）或 100%EC。因此，这三种“乳液”中的液滴分别为全液态、部分固态和全固态。在存在 22mM CaCl2 的情况下，混合的 TD+EC 液滴最有效地抑制相分离，而 EC 乳液则完全不能防止相分离。在 32mM CaCl2 下，乳液倾向于促进相分离，这可能是由于增强了钙离子诱导的液滴聚集。还测量了两个宏观分离相之间的表观界面粘度（ηi）。在半固态混合液滴存在下，ηi=25mNsm(-1)，显著高于纯（液态）TD 液滴（15mNsm(-1)）或纯固态 EC 液滴（12mNsm(-1)）或不存在液滴时（<3mNsm(-1)）。共焦显微镜显示，相分离区域的微观结构也取决于油滴的组成，因此推测混合乳液液滴的影响更为显著，是因为它们通过部分聚结在界面上形成了更强的网络。因此，控制液滴的界面聚集程度可能是影响生物聚合物混合物相分离过程的一种方法。
