Rediguieri Camila F, de Freitas Osvaldo, Lettinga M Paul, Tuinier Remco
Department of Pharmaceutical Sciences, University of São Paulo (FCFRP-USP), Avenida do Café s/n, Ribeirão Preto, SP, Brazil.
Biomacromolecules. 2007 Nov;8(11):3345-54. doi: 10.1021/bm7004438.
The instability of polysaccharide/protein mixtures occurs because of either thermodynamic incompatibility or complexation. We studied which instability mechanism dominated given the external conditions. Therefore the effect of temperature, pH, and biopolymer concentration on the phase separation of pectin/caseinate mixtures was investigated. At pH > 6, thermodynamic incompatibility with spinodal decomposition was observed in pectin/caseinate mixtures resulting in the formation of water-in-water emulsions in intermediate stages of the phase separation process. The demixing rate of these emulsions and appearance of two macroscopic phases (lower phase enriched with caseinate and upper phase with pectin) was retarded when the pectin concentration increased or when the storage temperature decreased due to a higher viscosity of the mixtures at those conditions. As the pH of the mixture was lowered below 6, pectin accumulated in the caseinate-rich phase. Complexation of pectin and caseinate led to the formation of microparticles (approximately 3 microm), whose shape depends on the biopolymer concentration ratio and rate of acidification. These pectin/caseinate particles do not coalesce and are insensitive to salt addition.
多糖/蛋白质混合物的不稳定性是由热力学不相容性或络合作用引起的。我们研究了在给定外部条件下哪种不稳定性机制起主导作用。因此，研究了温度、pH值和生物聚合物浓度对果胶/酪蛋白酸盐混合物相分离的影响。在pH>6时，果胶/酪蛋白酸盐混合物中观察到与旋节线分解相关的热力学不相容性，导致在相分离过程的中间阶段形成水包水乳液。当果胶浓度增加或储存温度降低时，由于混合物在这些条件下具有较高的粘度，这些乳液的分层速率和两个宏观相（富含酪蛋白酸盐的下层相和富含果胶的上层相）的出现会延迟。当混合物的pH值降低到6以下时，果胶会在富含酪蛋白酸盐的相中积累。果胶与酪蛋白酸盐的络合导致形成微粒（约3微米），其形状取决于生物聚合物浓度比和酸化速率。这些果胶/酪蛋白酸盐颗粒不会聚结，并且对添加盐不敏感。
