Department of Food Science and Technology, School of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece.
J Colloid Interface Sci. 2012 Jun 1;375(1):50-9. doi: 10.1016/j.jcis.2012.02.048. Epub 2012 Mar 3.
The sol-gel transition of aqueous barley β-glucan solutions which undergo gelation with ageing has been studied by conventional bulk rheology, phase contrast microscopy and particle tracking microrheology. Characterisation of the primary structure of the β-glucan isolate was carried out by enzymic methods and HPLC. The Brownian diffusion of fluorescent microspheres (0.75 μm diameter, carboxylate-coated particles) was used to probe the spatial mechanical properties of the gelling systems at the scale of microns; the potential use of passive particle tracking to study biopolymer gelling systems that present spatial heterogeneities is thus explored. For the β-glucan gels cured at 25°C both microrheology and bulk rheology revealed that with increasing the polysaccharide concentration the gelation time decreased, while the gelation rate and gel strength of the barley β-glucan gels increased. The particle tracking method had higher sensitivity and could map molecular ordering and structural heterogeneities in the evolving polysaccharide network at a micro-level. That is, different size pores were generated upon ageing with regions of depleted or less amount of β-glucan molecules. Furthermore, this method could detect changes in the fine structure of the system before such events can be registered by bulk rheological measurements; i.e. microheterogeneity and aggregation of β-glucan chains were revealed by particle tracking at earlier temporal stages of the experiment.
通过常规的体相流变学、相差显微镜和粒子追踪微流变学研究了具有老化凝胶化作用的水性大麦β-葡聚糖溶液的溶胶-凝胶转变。通过酶法和高效液相色谱法对β-葡聚糖分离物的一级结构进行了表征。荧光微球（直径 0.75μm，羧基涂层颗粒）的布朗扩散用于探测微米尺度下凝胶体系的空间力学性质；因此，探索了被动粒子跟踪在研究具有空间异质性的生物聚合物凝胶体系中的潜在应用。对于在 25°C 下固化的β-葡聚糖凝胶，微流变学和体相流变学都表明，随着多糖浓度的增加，凝胶时间缩短，而大麦β-葡聚糖凝胶的凝胶速率和凝胶强度增加。粒子追踪法具有更高的灵敏度，可以在微观水平上绘制出不断演变的多糖网络中的分子有序性和结构异质性。也就是说，在老化过程中会产生不同大小的孔，其中β-葡聚糖分子的数量减少或减少。此外，该方法可以在通过体相流变学测量可以记录的此类事件之前检测到系统的精细结构变化；也就是说，在实验的早期阶段，通过粒子跟踪可以揭示β-葡聚糖链的微异质性和聚集。
