Coagulation properties of ultrafiltered milk retentates measured using rheology and diffusing wave spectroscopy
Coagulation properties of ultrafiltered milk retentates measured using rheology and diffusing wave spectroscopy
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DOI：
10.1016/j.foodres.2011.02.018
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发表时间：
2011-05
影响因子：
8.1
通讯作者：
S. Sandra;C. Cooper;M. Alexander;M. Corredig
中科院分区：
文献类型：
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作者：
S. Sandra;C. Cooper;M. Alexander;M. Corredig
超滤浓缩牛奶对凝乳酶的影响已被广泛研究，因为它在乳制品技术中引起了极大的兴趣。尽管有许多关于不同浓度下形成的乳凝胶的质地和微观结构的报告，但对于浓度对聚集之前阶段的影响或浓度如何影响胶束之间的相互作用知之甚少。本研究旨在研究通过超滤（无渗滤）浓缩至 3× 和 5× (v/v) 的牛奶的凝乳行为，并将其与脱脂牛奶进行比较。酪蛋白胶束在静态条件下的散射特性表明，它们在 5 倍浓度（胶束体积分数，φ=0.5）下偏离硬球行为。在所测试的三种不同酪蛋白浓度（1×、3×和5×）中，凝乳酶过程中酪蛋白巨肽的释放没有显着差异。通过扩散波光谱和流变学检测，凝乳酶凝固时间也没有显着差异。由于网络中的键数量增加，浓缩牛奶样品形成的凝胶比普通牛奶明显（p 值<0.05）更硬。由于总体颗粒间距离的减小和碰撞频率的增加，牛奶浓度的水平还加速了胶束的空间分布和浊度变化率的变化。对浓缩牛奶样品的原位研究表明，凝乳酶凝固随浓度的变化仅仅是拥挤效应的一个原因。
The effect of concentration of milk by ultrafiltration on renneting has been widely studied as it is of great interest in dairy technology. Although a number of reports are available on the texture and microstructure of the milk gels formed at various concentrations, very little is understood on the effect of concentration on the stages preceding aggregation, or how concentration may affect the interactions between micelles. This study aims to investigate the renneting behavior of milk concentrated by ultrafiltration (without diafiltration) to 3× and 5× (v/v) and compare it to that of skim milk. The scattering properties of the casein micelles under quiescent conditions suggest that they deviate from hard-sphere behavior at 5× concentration (micelle volume fraction, ϕ=0.5). The release of the caseinomacropeptide during renneting was not significantly different amongst the three different casein concentrations tested (1×, 3×, and 5×). No significant differences were also noted in the rennet coagulation time as detected by both diffusing wave spectroscopy and rheology. Concentrated milk samples formed significantly (p-value<0.05) stiffer gels than regular milk due to an increased number of bonds in the network. The level of milk concentration also accelerated a change in the spatial distribution and rate of change of turbidity of the micelles because of a decrease in the overall inter-particle distance and increased collision frequencies. This in situ investigation of concentrated milk samples suggested that the changes in rennet coagulation with concentration are merely a cause of crowding effects.