Moschakis Thomas, Murray Brent S, Dickinson Eric
Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, UK.
J Colloid Interface Sci. 2005 Apr 15;284(2):714-28. doi: 10.1016/j.jcis.2004.10.036.
The time-dependent evolution of the phase-separated microstructure of a caseinate-stabilised emulsion containing xanthan gum added before emulsification has been investigated by confocal laser scanning microscopy, image analysis and rheology. Moderately low levels of xanthan addition lead to depletion flocculation and gravity-induced phase separation. Increasing the polysaccharide concentration causes immobilisation of the microstructure due to an increase in the local viscoelasticity: that is, the emulsion structure cannot easily rearrange to expel xanthan-enriched aqueous serum phase because a weak gel-like network is generated. The effect of xanthan on the evolving microstructure of phase-separated regions, which reflects indirectly the local emulsion micro-rheology, has been estimated from image analysis of time sequences of confocal micrographs. A comparison has been made between object shape analysis using four different shape descriptors. The roundness parameter has been found to be a convenient descriptor for reliably quantifying the structural change in terms of the relaxation rate of xanthan-rich aqueous drops. The Taylor parameter has been used to link the kinetics of drop relaxation to the time-dependent small-deformation rheological behaviour. The analysis of the combined experimental data reveals the difficulty of relating the evolving microstructure to bulk rheological measurements.
通过共聚焦激光扫描显微镜、图像分析和流变学研究了在乳化前添加黄原胶的酪蛋白酸盐稳定乳液相分离微观结构的时间依赖性演变。适度低水平的黄原胶添加会导致耗尽絮凝和重力诱导的相分离。由于局部粘弹性增加，多糖浓度的增加会导致微观结构固定化：也就是说，乳液结构不易重新排列以排出富含黄原胶的水相血清，因为会产生弱凝胶状网络。黄原胶对相分离区域不断演变的微观结构的影响间接反映了局部乳液微观流变学，已通过共聚焦显微照片时间序列的图像分析进行了估计。使用四种不同形状描述符对物体形状分析进行了比较。已发现圆度参数是一种方便的描述符，可用于根据富含黄原胶的水滴的松弛率可靠地量化结构变化。泰勒参数已用于将液滴松弛动力学与时间依赖性小变形流变行为联系起来。对综合实验数据进行分析后发现，很难将不断演变的微观结构与整体流变测量联系起来。
