Baussay Karine, Durand Dominique, Nicolai Taco
Polymères, Colloïdes, Interfaces, UMR CNRS, Université du Maine, 72085 Le Mans Cedex 9, France.
J Colloid Interface Sci. 2006 Dec 15;304(2):335-41. doi: 10.1016/j.jcis.2006.09.059. Epub 2006 Sep 26.
The effect of gelation of the polysaccharide phase on the phase separation was investigated for mixtures of anionic polysaccharide (kappa-carrageenan) and globular protein (beta-lactoglobulin) clusters at pH 7 well above the iso-electric point. Gelation of kappa-carrageenan was induced by cooling in the presence of KCl. In the liquid state the protein clusters phase-separate into relatively dense micro-domains. When the polysaccharide phase gelled during cooling, the turbidity of the systems decreased dramatically. Light scattering experiments showed that the density of the micro-domains decreased, while microscopy showed that the number and size was not strongly modified. It is concluded that smaller protein clusters leave the micro-domains when kappa-carrageenan gels. The effect could be reversed by reheating the samples and thus melting the gel and was observed for repeated heating and cooling cycles. The effect of gelation on phase separation decreases with increasing polysaccharide concentration and with ageing of the liquid mixture. The latter is caused by the formation of bonds between the protein clusters in the micro-domains that slowly reinforce with time.
在远高于等电点的pH 7条件下，研究了多糖相凝胶化对阴离子多糖（κ-卡拉胶）和球状蛋白（β-乳球蛋白）聚集体混合物相分离的影响。κ-卡拉胶的凝胶化是通过在KCl存在下冷却诱导的。在液态时，蛋白质聚集体相分离成相对致密的微区。当多糖相在冷却过程中凝胶化时，体系的浊度急剧下降。光散射实验表明微区的密度降低，而显微镜观察表明其数量和尺寸没有明显改变。得出的结论是，当κ-卡拉胶凝胶化时，较小的蛋白质聚集体离开微区。通过重新加热样品使凝胶熔化可以逆转这种效应，并且在反复的加热和冷却循环中都能观察到。凝胶化对相分离的影响随着多糖浓度的增加和液体混合物的老化而降低。后者是由微区中蛋白质聚集体之间形成的键随着时间缓慢增强所导致的。
